47.5 MB - The Whole Building Design Guide

Risk Management SeriesDesign Guidefor Improving Critical Facility Safetyfrom Flooding and High WindsFEMA 543 / January 2007FEMA

FEMA 543 / January 2007Risk Management SeriesDesign Guide forImproving Critical FacilitySafety from Flooding andHigh WindsProviding Protection to People and Buildings

Any opinions, findings, conclusions, or recommendationsexpressed in this publication do not necessarily reflect the views ofFEMA. Additionally, neither FEMA or any of its employees makesany warrantee, expressed or implied, or assumes any legal liabilityor responsibility for the accuracy, completeness, or usefulness ofany information, product, or process included in this publication.Users of information from this publication assume all liabilityarising from such use.

FOREWORD AND ACKNOWLEDGMENTSBACKGROUNDOn August 29, 2005, Hurricane Katrina caused extensivedamage to the coast along the Gulf of Mexico, resultingin an unprecedented relief, recovery, and reconstructioneffort. This reconstruction presents a unique opportunity to rebuildthe communities and public infrastructure using the latesthazard mitigation techniques proven to be more protective of livesand property.Critical facilities comprise all public and private facilities deemedby a community to be essential for the delivery of vital services,protection of special populations, and the provision of other servicesof importance for that community. This manual concentrateson a smaller group of facilities that are crucial for protecting thehealth and safety of the population: health care, educational, andemergency response facilities.The Design Guide for Improving Critical Facility Safety from Floodingand High Winds (FEMA 543) was developed with the support ofthe Federal Emergency Management Agency (FEMA) RegionIV in the aftermath of Hurricane Katrina. This manual recommendsincorporating hazard mitigation measures into all stagesand at all levels of critical facility planning and design, for bothnew construction and the reconstruction and rehabilitation ofexisting facilities. It provides building professionals and decisionmakerswith information and guidelines for implementinga variety of mitigation measures to reduce the vulnerability todamage and disruption of operations during severe flooding andhigh-wind events. The underlying theme of this manual is thatby building more robust critical facilities that will remain oper-Foreword AND ACKNOWLEDGMENTS

ational during and after a major disaster, people’s lives and thecommunity’s vitality can be better preserved and protected.This manual is a part of FEMA’s Risk Management Series, whichprovides guidelines for mitigating against multiple hazards. Theseries emphasizes mitigation best practices for specific buildinguses, such as schools, hospitals, higher education buildings,multi-family dwellings, commercial buildings, and light industrialfacilities.OBJECTIVESThe poor performance of many critical facilities in the affectedareas was not unique to Hurricane Katrina. It was observed in numeroushurricanes dating back more than three decades. Severalreasons may explain this kind of performance. In many cases thedamaged facilities were quite old and were constructed well beforethe introduction of modern codes and standards. Some ofthe older facilities were damaged because building componentshad deteriorated as a result of inadequate maintenance. Many facilitiesoccupy unsuitable buildings that were never intended forthis type of use. Some newer facilities suffered damage as a resultof deficiencies in design and construction or the application of inappropriatedesign criteria and standards.The primary objective of this manual is to assist the buildingdesign community and local officials and decisionmakers inadopting and implementing sound mitigation measures that willdecrease the vulnerability of critical facilities to major disasters.The goals of this manual are to:m Present and recommend the use of building design featuresand building materials and methods that can improve theperformance of critical facilities in hazard-prone areas duringand after flooding and high-wind events.m Introduce and provide guidelines for implementing floodingand high-wind mitigation best practices into the process ofdesign, construction, and operation and maintenance ofcritical facilities.iiForeword AND ACKNOWLEDGMENTS

SCOPETo aid in the reconstruction of the Gulf Coast in the wake ofHurricane Katrina, this manual presents an overview of the principalplanning and design considerations for improving theperformance of critical facilities during, and in the aftermath of,flooding and high-wind events. It provides design guidance andpractical recommendations for protecting critical facilities andtheir occupants against these natural hazards. The focus is on thedesign for new construction, but this manual also addresses rehabilitationof existing critical facilities. It presents incrementalapproaches that can be implemented over time to decrease thevulnerability of buildings, but emphasizes the importance of incorporatingthe requirements for mitigation against flooding andhigh winds into the planning and design of critical facilities fromthe very beginning of the process.The material and recommendations contained in this manual areapplicable to many facilities, but address primarily the followingcritical facilities:m Schoolsm Health Care Facilitiesm Fire Stationsm Police Stationsm Emergency Operation Centers (EOCs)The information presented in this manual provides a comprehensivesurvey of the methods and processes necessary to protectcritical facilities from natural hazards, but is necessarily limited.It is not expected that the reader will be able to use this informationdirectly to develop plans and specifications. It is intended asan introduction to a broader understanding of the fundamentalapproaches to risk mitigation planning and design. This will helpbuilding officials and professionals move on to the implementationphase that involves consultants, procurement personnel, andproject administrators, with a better grasp of the task in front ofthem—improving the safety and welfare of their communities.Foreword AND ACKNOWLEDGMENTSiii

TARGET AUDIENCEThis manual describes various mitigation measures that have beensuccessful in the past and could be implemented quickly, especiallyin areas recovering from a disaster. The intended audience comprisesthe people who own, operate, design, build, and maintaincritical facilities in hazard-prone areas. This includes planning,building design, and construction professionals working for privateorganizations, State and local government officials working inthe building sector, and relevant technical and management personnelinvolved with the operation of critical facilities.TRAININGIn tandem with the publication of this manual, FEMA has developeda companion training course targeted to building designprofessionals and facility managers interested in improving thefunctionality of critical facilities in natural disasters. For transfer ofits content, FEMA will promote a series of workshops directed atthese professionals and others involved in planning, design, construction,rehabilitation, and management of critical facilities inareas exposed to flooding and high winds.The training course emphasizes the best practices in mitigatingagainst flooding and winds hazards. It is organized around a seriesof exercises, starting with vulnerability analysis, and progressingthrough assessment of risks, assessment of building systems performance(especially the effects of physical damage on the facility’sfunctionality), and the selection of appropriate mitigation measuresto be incorporated into the design of critical facilities.The expansive scope of reconstruction activities in the aftermathof Hurricane Katrina requires that this course be initially offeredand delivered only to affected communities in the Gulf States.However, the relevance and usefulness of this course extends farbeyond the hurricane-prone regions, to areas exposed to otherwind hazards, as well as areas subject to all types of coastal and riverineflooding.ivForeword AND ACKNOWLEDGMENTS

ORGANIZATION AND CONTENTSThis manual is divided into four main chapters.Chapter 1 presents an overview of the principal design considerationsto help owners, managers, and designers whendetermining the location, building characteristics, and hazard resistanceof critical facilities. It outlines the basic principles anddesign tools for improving the safety of critical facilities exposedto flooding and high winds. It also provides guidelines for facilitymanagers and building professionals on how to coordinate theprocess of planning and design of critical facilities.Chapter 2 discusses the nature of flood forces and their effectson buildings. It outlines the procedures for risk assessment,and describes current mitigation methods for reducing the effectsof flooding. It underlines the need to avoid high-risk areasfor the construction of new critical facilities, and encouragesthe application of mitigation measures when critical facilitiesmust remain in high-risk areas. This chapter provides extensivereview of the requirements of the National Flood InsuranceProgram (NFIP), model building codes and other standards,as well as new FEMA policy updates resulting from the experiencesof Hurricanes Katrina and Rita.Chapter 3 discusses the effects of wind forces on the structuraland nonstructural building components of critical facilities. By reviewingnumerous examples of wind-induced damage to thesefacilities, it points out the best practices pertaining to new constructionand rehabilitation of existing facilities. It concentrateson building components most critical for protecting the uninterruptedoperation of critical facilities and provides detailedguidelines for improving their design and construction in hurricane-and tornado-prone areas.Chapter 4 discusses the performance of hospital, schools, andemergency response facilities (i.e., EOCs, and police and firerescue stations) during Hurricane Katrina. This chapter emphasizesthe lessons learned about the adverse effects on thefunctionality of critical facilities arising from damage to buildingsand contents, especially the ways that various types of physicaldamage disrupted their operations.Foreword AND ACKNOWLEDGMENTS

Appendix A contains a list of acronyms and Appendix B contains aglossary of terms that appear in this manual. Appendix C containsan overview of the FEMA grant programs available for fundingconstruction or rehabilitation of critical facilities.ACKNOWLEDGMENTSThe preparation of this document was sponsored by FEMARegion IV. It has been developed based on the work of several recentpublications (as listed below), new insights from the KatrinaMitigation Assessment Teams in the field, and other sources of informationon Hurricane Katrina. The principal and contributingauthors of the following documents are gratefully acknowledged:FEMA 424, Design Guide for Improving School Safety in Earthquakes,Floods, and High Winds; FEMA 489, Mitigation Assessment TeamReport for Hurricane Ivan in Alabama and Florida; FEMA RegionIV, Hurricane Mitigation: A Handbook for Public Facilities; FEMARegion X, Earthquake Hazard Mitigation Handbook for PublicFacilities; Structural Engineers Association of Washington (SEAW)Commentary on Wind Provisions (Volumes 1 and 2); and other referencedocuments presented in Chapter 1.For this manual, the following individuals are acknowledged:Authors:Rebecca C. Quinn, RCQuinn Consulting, Inc.Thomas L. Smith, TLSmith ConsultingBogdan Srdanovic, URSWilliam Coulbourne, URSJon Heintz, ATCLisa Scola, PBS&JWilbur H. Tusler, ConsultantDouglas A. Ramirez, PBS&JviForeword AND ACKNOWLEDGMENTS

William Brown, PBS&JPedro Escobar, PBS&JShaddy Shafie, PBS&JScott Sundberg, URSMilagros Nanita Kennett, FEMA, Project Officer, RiskManagement Series PublicationsContributors:Shabbar Saifee, FEMA, Project MonitorEric Letvin, URS, Project ManagerMark Matulik, ConsultantLawrence Frank, URSJohn Squerciati, DewberryWanda Rizer, design4impactMike Robinson, PBS&JManuel Perotin, PBS&JSusan Patton, URSRob Fernandez, URSJanet Frey, URSThe authors and editors gratefully acknowledge the invaluable assistanceand advice provided by the following reviewers:Christopher Arnold, Building Systems Development Inc.;Ronald B. Bailey, Bailey Engineering Corp.; Bob Baker, BBJEnvironmental Solutions, Inc.; Ron A. Cook, University of Florida;Jim Fields; Doug Fitts, St. Louis County Public Works; LoisForeword AND ACKNOWLEDGMENTSvii

Forster, FEMA; David Godschalk, University of North Carolina;Neil Grigg, Colorado State University; John Ingargiola, FEMA;Philip Keillor, American Society of Flood Plain Managers; LeonKloostra; Richard Kuchnicki, International Code Council;Lawrence Larson, ASFPM; Sheila McKinley, Christopher B. BurkeEngineering; Nancy McNabb, NFPA; Elliott Mittler; Ann Patton,Ann Patton Company; Dan Powell, FEMA; Dennis Quan, FEMA;Jim Rossberg, ASCE; Michael P. Sheerin, TLC Engineering forArchitecture; Emil Simiu, NIST; Robert Slynn, University ofFlorida; Alan Springett, FEMA; Thomas Sputo, University ofFlorida; Jim Tauby; Anton TenWolde; Scott Tezak, URS; DavidUnderwood; Wallace A. Wilson.This manual will be revised periodically and FEMA welcomescomments and suggestions for improvements in future editions.Please send your comments and suggestions via e-mail to:RiskManagementSeriesPubs@dhs.govviiiForeword AND ACKNOWLEDGMENTS

TABLE OF CONTENTSFOREWORD AND ACknowledgments........................................................................iBackground...........................................................................................................................iObjectives............................................................................................................................ iiScope ................................................................................................................................. iiiTarget Audience..................................................................................................................ivTraining ..............................................................................................................................ivOrganization and Contents................................................................................................. vAcknowledgements.............................................................................................................viChapter 1– Critical facility design considerations............................1-11.1 Introduction...................................................................................................................... 1-11.1.1 Critical Facilities................................................................................................1-21.1.2 Hurricane Katrina.............................................................................................1-31.2 Hazard Mitigation............................................................................................................. 1-71.2.1 Hazard Mitigation for Critical Facilities..........................................................1-71.2.2 Site Selection ....................................................................................................1-81.2.3 Facility Design ................................................................................................1-101.3 Performance-Based Design................................................................................................ 1-141.3.1 Background.....................................................................................................1-141.3.2 Prescriptive vs. Performance-Based Design...................................................1-151.3.3 The Process of Performance-Based Design of Critical Facilities..................1-161.3.4 Acceptable Risk and Performance Levels......................................................1-171.3.5 Performance-Based Flood Design .................................................................1-221.3.6 Performance-Based High-Wind Design ........................................................1-231.4 References..................................................................................................................... 1-25table of contentsix

Chapter 2– Making Critical facilities safe from flooding...........2-12.1 General Design Considerations............................................................................................. 2-12.1.1 Nature and Characteristics of Flooding...........................................................2-12.1.1.1 Probability of Occurrence or Frequency......................................2-72.1.1.2 Hazard Identification and Flood Data..........................................2-92.1.1.3 Design Flood Elevation ...............................................................2-152.1.1.4 Advisory Base Flood Elevation ....................................................2-162.1.2 Flood Loads.....................................................................................................2-172.1.2.1 Design Flood Depth ....................................................................2-182.1.2.2 Design Flood Velocity—Riverine.................................................2-192.1.2.3 Design Flood Velocity—Coastal...................................................2-202.1.2.4 Hydrostatic Loads.........................................................................2-212.1.2.5 Hydrodynamic Loads...................................................................2-232.1.2.6 Debris Impact Loads....................................................................2-252.1.2.7 Erosion and Localized Scour.......................................................2-272.1.3 Floodplain Management Requirements and Building Codes .....................2-282.1.3.1 Overview of the NFIP...................................................................2-292.1.3.2 Summary of the NFIP Minimum Requirements .......................2-312.1.3.3 Executive Order 11988 and Critical Facilities ...........................2-332.1.3.4 Scope of Model Building Codes and Standards ........................2-342.2 Critical Facilities Exposed to Flooding ................................................................................. 2-372.2.1 Evaluating Risk and Avoiding Flood Hazards................................................2-372.2.1.1 Benefits/Costs: Determining Acceptable Risk...........................2-382.2.1.2 Identifying Flood Hazards at Critical Facilities Sites..................2-402.2.1.3 Critical Facilities as Emergency Shelters ....................................2-402.2.2 Vulnerability: What Flooding Can Do to Existing Critical Facilities............2-412.2.2.1 Site Damage..................................................................................2-42table of contents

2.2.2.2 Structural Damage.......................................................................2-432.2.2.3 Nonstructural Damage.................................................................2-462.2.2.4 Utility System Damage.................................................................2-492.2.2.5 Contents Damage.........................................................................2-522.3 Requirements and Best Practices in Special Hazard Areas...................................................... 2-552.3.1 Risk Reduction in “A Zones” .........................................................................2-552.3.1.1 Site Modifications.........................................................................2-552.3.1.2 Elevation Considerations.............................................................2-582.3.1.3 Flood-Resistant Materials ............................................................2-622.3.1.4 Dry Floodproofing Considerations ............................................2-642.3.2 Risk Reduction in “V Zones” .........................................................................2-682.3.2.1 Elevation Considerations.............................................................2-692.3.2.2 Flood-Resistant Materials ............................................................2-702.3.3 Risk Reduction in “Coastal A Zones” ............................................................2-702.3.4 Risk Reduction in Hurricane Storm Surge Areas ........................................2-722.3.5 Risk Reduction for Related Facilities.............................................................2-732.3.5.1 Access Roads ................................................................................2-732.3.5.2 Utility Installations ......................................................................2-742.3.5.3 Potable Water and Wastewater Systems......................................2-762.3.5.4 Storage Tank Installations ...........................................................2-772.3.5.5 Accessory Structures ....................................................................2-772.4 Risk Reduction for Existing Critical Facilities........................................................................ 2-782.4.1 Introduction....................................................................................................2-782.4.2 Site Modifications ...........................................................................................2-792.4.3 Additions .........................................................................................................2-812.4.4 Repairs, Renovations, and Upgrades.............................................................2-822.4.5 Retrofit Dry Floodproofing ...........................................................................2-83table of contentsxi

2.4.6 Utility Installations .........................................................................................2-842.4.7 Potable Water and Wastewater Systems.........................................................2-862.4.8 Other Damage Reduction Measures .............................................................2-872.4.9 Emergency Measures......................................................................................2-882.5 Checklist for Building Vulnerability of Flood-Prone Critical Facilities..............................................2-912.6 References and Sources of Additional Information...................................................................2-100Chapter 3– Making Critical facilities safe from High wind........3-13.1 General Design Considerations............................................................................................. 3-13.1.1 Nature of High Winds.......................................................................................3-23.1.2 Probability of Occurrence................................................................................3-53.1.3 Wind/Building Interactions.............................................................................3-83.1.4 Building Codes................................................................................................3-183.1.4.1 Scope of Building Codes..............................................................3-183.1.4.2 Effectiveness and Limitations of Building Codes.......................3-193.2 Critical Facilities Exposed to High Winds............................................................................. 3-233.2.1 Vulnerability: What High Winds Can Do to Critical Facilities......................3-233.2.1.1 Types of Building Damage...........................................................3-233.2.1.2 Ramifications of Damage.............................................................3-263.2.2 Evaluating Critical Facilities for Risk From High Winds..............................3-293.2.2.1 New Buildings...............................................................................3-293.2.2.2 Existing Buildings.........................................................................3-303.3 Critical Facility Design Considerations................................................................................. 3-323.3.1 General Design Considerations......................................................................3-323.3.1.1 Site ................................................................................................3-333.3.1.2 Building Design..............................................................................3-34xiitable of contents

4.2.6 Building Envelope.............................................................................................4-114.2.7 Utility Plumbing Systems..................................................................................4-164.2.8 Mechanical and Electrical Systems...................................................................4-184.2.10 Communications Systems.................................................................................4-214.2.11 Nonstructural and Other Systems....................................................................4-234.2.12 Summary............................................................................................................4-254.3 Educational Facilities ....................................................................................................... 4-264.3.1 Background.......................................................................................................4-264.3.2 Effects of Flooding............................................................................................4-284.3.3 Effects of High Winds.......................................................................................4-294.3.4 Site Selection.....................................................................................................4-304.3.5 Architectural Design.........................................................................................4-324.3.6 Structural Systems.............................................................................................4-344.3.7 Building Envelope.............................................................................................4-354.3.8 Utility Systems....................................................................................................4-394.3.9 Mechanical and Electrical Systems...................................................................4-394.3.10 Nonstructural and Other Systems....................................................................4-404.3.11 Equipment and Auxiliary Installations............................................................4-424.3.12 Summary............................................................................................................4-434.4 Emergency Response Facilities ........................................................................................... 4-454.4.1 Background.......................................................................................................4-454.4.2 Effects of Flooding............................................................................................4-474.4.3 Effects of High Winds.......................................................................................4-484.4.4 Site Selection.....................................................................................................4-484.4.5 Architectural Design.........................................................................................4-514.4.6 Structural Systems.............................................................................................4-544.4.7 Building Envelope.............................................................................................4-56table of contentsxv

4.4.8 Utility Plumbing Systems..................................................................................4-614.4.9 Mechanical and Electrical Systems ..................................................................4-624.4.10 Communications Systems.................................................................................4-654.4.11 Equipment and Auxiliary Installations............................................................4-664.4.12 Summary............................................................................................................4-67APPENDICESAppendix A Acronyms........................................................................................................... A-1Appendix BGlossary of Terms.................................................................................................B-1Appendix C FEMA Mitigation Programs.................................................................................... C-1Public Assistance (Section 406)............................................................................ C-4Hazard Mitigation Grant Program (Section 404)............................................... C-7Pre-Disaster Mitigation (Section 203) ................................................................. C-8Flood Mitigation Assistance Program.................................................................. C-9xvitable of contents

CRITICAL FACILITY DESIGN CONSIDERATIONS 11.1 INTRODUCTIONThis chapter introduces the role of hazard mitigation in theplanning, design, and construction of critical facilities. Itdescribes the way building design determines how well acritical facility is protected against natural hazard risks, specificallythe risks associated with flooding and high winds. Criticalfacilities, and the functions they perform, are the most significantcomponents of the system that protects the health, safety,and well-being of communities at risk.The devastating effects of recent hurricanes, especially HurricaneKatrina, underscored the vulnerability of coastal areas of theUnited States, the fastest growing regions of the country. The populationpressure and the aggressive coastal development in areassubject to hurricanes and coastal storms created the conditionsthat require careful consideration of the effects of natural hazardson the sustainability of this development. One of the most importantdeterminants of the sustainability of coastal communities isthe reliability of their physical and social infrastructure. The communitiesthat cannot rely on their own critical infrastructure areextremely vulnerable to disasters. This is why the design of criticalfacilities to improve their resistance to damage, and their abilityto function without interruption during and in the aftermath ofhazard events, deserves special attention.To ensure safe and uninterrupted operation of critical facilities,which is vital in the post-disaster period, facility owners must incorporatea comprehensive approach to identify hazards andCRITICAL FACILITY DESIGN CONSIDERATIONS1-1

avoid them when feasible. In cases when exposure to hazards isunavoidable, it is recommended that they build new facilities, orrehabilitate the existing ones to resist the forces and conditions associatedwith these hazards.1.1.1 Critical FacilitiesIn general usage, the term “critical facilities” is used to describeall manmade structures or other improvements that, because oftheir function, size, service area, or uniqueness, have the potentialto cause serious bodily harm, extensive property damage, ordisruption of vital socioeconomic activities if they are destroyed,damaged, or if their functionality is impaired.Critical facilities commonly include all public and private facilitiesthat a community considers essential for the delivery of vitalservices and for the protection of the community. They usuallyinclude emergency response facilities (fire stations, police stations,rescue squads, and emergency operation centers [EOCs]),custodial facilities (jails and other detention centers, long-termcare facilities, hospitals, and other health care facilities), schools,emergency shelters, utilities (water supply, wastewater treatmentfacilities, and power), communications facilities, and any other assetsdetermined by the community to be of critical importance forthe protection of the health and safety of the population. The adverseeffects of damaged critical facilities can extend far beyonddirect physical damage. Disruption of health care, fire, and policeservices can impair search and rescue, emergency medical care,and even access to damaged areas.The number and nature of critical facilities in a communitycan differ greatly from one jurisdiction to another, and usuallycomprise both public and private facilities. In this sense, eachcommunity needs to determine the relative importance of thepublicly and privately owned facilities that deliver vital services,provide important functions, and protect special populations.Minimum requirements for the design of new critical facilitiesand for improvements to existing facilities are found in the modelbuilding codes and the design and construction standards. ASCE7, Minimum Design Loads for Buildings and Other Structures, is the1-2 CRITICAL FACILITY DESIGN CONSIDERATIONS

est known standard. Published by the American Society of CivilEngineers (ASCE), it classifies buildings and other structures intofour categories based on occupancy. Most critical facilities fall intoCategory III or Category IV, described below:Category I includes buildings and other structures whose failurewould represent a low hazard to human life, such as agriculturalbuildings and storage facilities.Category II includes all buildings not specifically included in othercategories.Category III includes buildings and other structures that representa substantial hazard to human life in the event of failure. They includebuildings with higher concentrations of occupants (i.e.,where more than 300 people congregate in one area). These aretypically educational facilities with capacities greater than 250 forelementary and secondary facilities, 500 for colleges and adult educationfacilities, or 150 for daycare facilities.Category IV includes essential facilities such as hospitals, fire andpolice stations, rescue and other emergency service facilities,power stations, water supply facilities, aviation facilities, and otherbuildings critical for the national and civil defense.This manual concentrates on a number of critical or, as they aresometimes called, essential facilities, that deal with health andsafety in emergencies, and include health care facilities, police andfire stations, EOCs, and schools. These facilities are chosen becauseof their vitally important role in protecting the health and safety ofthe community. Although limited in scope to several specific typesof facilities, the information and recommendations in this manualare valuable and applicable to other types of critical facilities locatedin areas prone to flooding and exposed to high winds.1.1.2 Hurricane KatrinaAlthough not the strongest storm to hit the coast of the UnitedStates, Hurricane Katrina caused the greatest disaster in the nation'shistory. The hurricane made its first landfall on August 25,2005, on the southeast coast of Florida as a Category 1 hurricane.CRITICAL FACILITY DESIGN CONSIDERATIONS1-3

It then crossed Florida into the Gulf of Mexico, where it gainedstrength to a Category 5 hurricane. Before making its secondlandfall near Buras in southeast Louisiana, Katrina weakened toa Category 3 hurricane. Moving across southeast Louisiana, Katrinacontinued northward, pushing storm surge into coastal areasof Alabama, Mississippi, and Louisiana. After crossing over LakeBorgne, it finally made a third landfall as a Category 3 hurricanenear Pearlington, Mississippi, at the Louisiana/Mississippi border(see Figures 1-1 and 1-2). The hurricane caused extensive devastationalong the gulf coast, with southeast Louisiana and the coast ofMississippi bearing the brunt of the catastrophic damage.Wind damage was widespread and severe in many areas; however,the greatest damage was caused by Hurricane Katrina'sstorm surge flooding. Although the storm weakened froma powerful Category 5 to a Category 3 hurricane just beforemaking landfall in Louisiana and Mississippi, the storm surgeappears to have maintained a level associated with a Category5 hurricane. The surge built by the stronger winds over openwater could not dissipate as quickly as the wind speeds decreased,and the shallow depth of the off-shore shelf and theshape of the shoreline contributed to the high surge elevations.The Mississippi coastline experienced the highest storm surgeon record. The storm surge also contributed to failures of anumber of levees, notably the levee system that protects the Cityof New Orleans from Lake Borgne and Lake Pontchartrain. Anestimated 80 percent of the city subsequently flooded.The disaster was further compounded by the poor performanceof critical facilities during and after the storm. Critical facilitiestypically did not perform any better than ordinary commercialbuildings, but the extent of the damage to these facilities and thesubsequent disruption of their operations caused much greaterhardship. Facilities such as hurricane evacuation shelters, policeand fire stations, hospitals, and EOCs were severely damaged andmany were completely destroyed. Some facilities experienced aloss of function when critical support equipment, such as vehiclesand communication equipment, were damaged or destroyed.While most of the damage to critical facilities was caused by thestorm surge, wind damage also was widespread and substantial. Inseveral instances, critical facilities were destroyed completely ordamaged so severely that all the occupants had to be evacuated1-4 CRITICAL FACILITY DESIGN CONSIDERATIONS

Figure 1-1: Hurricane Katrina’s path through Louisiana and Mississippi(based on hurricane storm track data from the National Hurricane Center)CRITICAL FACILITY DESIGN CONSIDERATIONS1-5

Figure 1-2: Mississippi coast SLOSH NOAA dataSOURCE: National Oceanic and Atmospheric Administration (NOAA)after the hurricane had moved inland. The loss of so many criticalfacilities placed a severe strain on the emergency operations andrecovery efforts.The estimated death toll of Hurricane Katrina exceeded 1,800. Morethan 85 percent of casualties were recorded in Louisiana and about13 percent of victims lost their lives in Mississippi. Other deaths attributedboth directly and indirectly to Katrina were reported inFlorida, Alabama, Georgia, Kentucky, and Ohio. Hurricane Katrinaranks as the third deadliest hurricane in the United States, surpassedonly by the Texas Hurricane at Galveston in 1900, where atleast 6,000 and possibly as many as 10,000 lives were lost, and theFlorida Hurricane at Lake Okeechobee in 1928, which claimed2,500 lives. Estimated total economic losses from Katrina are inexcess of $150 billion, and insured losses are $40 billion, makingKatrina the most expensive natural disaster in the nation’s history.1-6 CRITICAL FACILITY DESIGN CONSIDERATIONS

Since 1977, Federal agencies have beencharged by Executive Order 11988 toprovide leadership “to reduce the risk offlood loss, to minimize the impact of floodson human safety, health and welfare, andto restore and preserve the natural andbeneficial values served by floodplains incarrying out their responsibilities for (1)acquiring, managing, and disposing ofFederal lands and facilities; (2) providingfederally undertaken, financed, or assistedconstruction and improvements; and (3)conducting Federal activities and programsaffecting land use, including but not limited towater and related land resources planning,regulating, and licensing activities.”planning process, States and communitiesare encouraged to identify existing critical facilitiesand to evaluate their vulnerability tonatural hazards. To qualify for certain Federalmitigation grant programs, projects to rehabilitatecritical facilities must be consistent withState and local mitigation plans. AppendixC provides an overview of conditions and requirementsfor obtaining funding assistancefrom major mitigation funding programsadministered by the Federal Emergency ManagementAgency (FEMA).There is no single procedure mandated for theplanning, site selection, and design of criticalfacilities, because none can be assumed to beuniversally applicable. The decision to build acritical facility depends on many factors and requiresa rigorous and comprehensive analysis of all the conditionsthat may affect the operation of a facility. This manual primarily addressesthe design of new facilities and measures to improve thedisaster resistance of existing facilities exposed to flooding andhigh winds, based on the assumption that all other alternatives tominimize or avoid such risks have been thoroughly evaluated andrejected as infeasible or impractical. It is outside the scope of thismanual to try to depict in detail this evaluation process in its fullrange and complexity. Communities, as well as the owners and operatorsof critical facilities, must evaluate all alternatives, assess allrisks, and consider all short-term and long-term effects of proposedprojects, whenever construction or rehabilitation of these facilitiesis considered. Careful analysis of alternatives and the potential adverseeffects of exposing critical facilities to natural hazards is alsointended to help identify the most appropriate hazard-resistantmeasures when avoidance is not practical.1.2.2 Site SelectionSite selection is a particularly significant step when planning newcritical facilities or when planning substantial improvements toexisting facilities in hazard-prone areas. The earliest steps in theplanning process should be to identify hazards and assess the1-8 CRITICAL FACILITY DESIGN CONSIDERATIONS

isks for the facility at the proposed site. Inaddition, alternative solutions should beconsidered in order to avoid site-specific hazardslike floods. After decisions about thebuilding location have been made, hazardmitigation involves acquiring a full understandingof the prevalent hazards andconsidering all appropriate hazard-resistancemeasures to ensure the uninterrupted operationof critical facilities.All work on critical facilities must meet theminimum requirements of building codes andrelated regulations. However, the importanceof uninterrupted operation of criticalfacilities frequently makes it necessary to gobeyond the code requirements to provideacceptable levels of protection for the facility’sfunctionality during, and in the immediateaftermath of, a hazard event.Typically, the selection of a site for a critical facility is based onspecific functions of a facility and the characteristics of its servicearea. In cases where critical facilities may be exposed to floodingand wind hazards, it is recommended that the final site decisionbe made only after all alternative sites have been evaluated forhazard exposure and the resulting effects of the hazard exposureon the design, construction, and operation of a facility.Considering that critical facilities should avoid hazard-prone areas,site selection may sometimes be a difficult and prolonged process.This is especially true in situations when the facility service requirementscannot be easily reconciled with requirements to minimizethe exposure to hazards. Sometimes a facility, like a fire station forexample, cannot fulfill its rapid response function if it is locatedoutside the hazard zone, far from the area the facility is intendedto serve. Additionally, site selection is not always controlled by thecommunity. Many local jurisdictions report that the high cost andthe scarcity of available land can severely limit the consideration ofalternative locations. The consequences of accepting a flood-pronesite include not only the potential physical damage, but also theloss of services provided by the critical facility. This loss of servicecan adversely affect the community as a whole, both in the immediatepost-event period and during its long-term recovery. Section2.5.1 contains a discussion and a number of questions that canhelp guide determinations about whether the risks associated withbuilding a critical facility in a floodplain are acceptable.If the site selection process determines that no other practicaland feasible alternatives are available and that a facility must belocated in a hazard-prone area, the highest level of protectionshould be a design priority.CRITICAL FACILITY DESIGN CONSIDERATIONS1-9

1.2.3 Facility DesignThe nature of services provided by critical facilities requiresthat designers and decisionmakers define a design objective ofachieving building performance levels beyond the minimum requirementsprescribed by the building code. While compliancewith the building code may satisfy the requirements to protect thefacility’s occupants, it may be insufficient to ensure the continuedoperation of the facility. When designing or rehabilitating a criticalfacility located in an area subject to high-wind or floodingrisks, this manual recommends a set of guidelines intended tominimize the interruption in operation of critical facilities, bothduring and in the aftermath of hazard events.m Conduct an in-house assessment of the facility needs, withthe assistance of decisionmakers and consultants. Publiccommittees may contribute advice and guidance throughoutthe programming and design process. For large programs,committees may acquire specialists at different stages asnecessary.m Determine the size and scope of the proposed program. Ina smaller area, an architect may be employed to assist thedecisionmakers with this task, possibly later becoming thedesign architect.m Assess the needs of the facility to determine the availability ofsuitable sites (and lease/purchase as necessary).m Develop occupant specifications, seeking advice from facilitymanagers and both in-house and consulting professionals.m Assess financial needs.m Identify financial resources, including alternative sources offunding (e.g., Federal and State programs, local taxes, bondissues, and utility fees).m Ensure funding (e.g., bond issue, establishment of utilitydistricts, etc.).1-10 CRITICAL FACILITY DESIGN CONSIDERATIONS

m Appoint a building program management staff (appointedofficials or a committee).m Determine the design and construction process (i.e.,conventional design and bid, design/build, or constructionmanagement).m Select and hire architects and other special design consultantsor design/build team members. The timing of this phasevaries depending on the number of variables.m Develop building programs, including building size, roomsize, equipment, and environmental requirements. This maybe done in-house, or architects and independent programconsultants may assist.m Appoint a local representative to the staff and a publicstakeholders committee for the design phase.m Develop designs with cost estimates. Hold public meetings,with the architects in attendance, and encourage public inputinto the design. Implement local area progress reviews.m Complete the design and solicit a local review of the contractdocuments.m Submit construction documents to the local jurisdiction andany permitting agencies for review and approval.m Submit documents to the building department.m Select the contractor (if bidding is used), or finalize design/build or construction management contracts.m Undertake critical facility construction.m Administer the construction contract.m Monitor the construction progress and conduct inspections, asrequired.m Complete contracted tasks.CRITICAL FACILITY DESIGN CONSIDERATIONS1-11

m Conduct inspections and provide proof of the architect’sacceptance.m Inspect the critical facility and obtain concurrence/acceptanceby the owner.m Commission the facility and occupy it.The sequence of the above steps may vary, depending on thecomplexity of the program; some steps may be implemented simultaneously.Figure 1-3 shows a flow chart of this typical process.Also shown (in the five boxes to the right) are specific activities relatedto designing for multiple hazards and how these activities fitinto the construction process.1-12 CRITICAL FACILITY DESIGN CONSIDERATIONS

-Figure 1-3: Process flow chart for decisionmakersCRITICAL FACILITY DESIGN CONSIDERATIONS1-13

1.3 PERFORMANCE-BASED DESIGNPerformance-based codes define acceptableor tolerable levels of risk for a variety ofhealth, safety, and public welfare issues.Currently available are the InternationalCode Council Performance Code forBuildings and Facilities by the InternationalCode Council (ICC, 2006), 101 Life SafetyCode (NFPA, 2006a), and the NFPA5000 Building Construction and SafetyCode (NFPA, 2006b) by the National FireProtection Association (NFPA). The ICCperformance code addresses all types ofbuilding issues, while the provisions of the101 Life Safety Code, “Performance-BasedOption,” address only issues related to “lifesafety systems.” The NFPA 5000 BuildingConstruction and Safety Code sets forth bothperformance and prescriptive options thatapply to all traditional building code issues.1.3.1 BackgroundThe model building codes define the minimum designrequirements to ensure occupants’ safety in critical facilities.Recent natural disasters have forced recognitionthat damage can occur even when buildingsare compliant with the building code.The fact that a large number of criticalfacilities in communities affected by HurricaneKatrina were shut down (frequentlyas a result of minor building or equipmentdamage) suggests that satisfying the minimumcode criteria may not be sufficientto ensure continued availability of criticalservices. Communities depend on the uninterruptedoperation of critical facilities,especially during and immediately followingnatural disasters. In order to meet that need,critical facilities should be designed and constructedaccording to criteria that result incontinued and uninterrupted provision ofcritical services.Building performance indicates how wella structure supports the defined needs ofits users. The term “performance,” as it relatesto critical facilities exposed to natural1-14 CRITICAL FACILITY DESIGN CONSIDERATIONS

hazards, usually refers to a building’s conditionafter a disaster, i.e., it signifies a level ofdamage or a load. Acceptable performanceindicates acceptable levels of damage or abuilding condition ,that allows uninterruptedfacility operation. Consequently, performance-baseddesign for critical facilities is theprocess or methodology used by design professionalsto create buildings that protect afacility’s functionality and the continued availabilityof services. This approach represents amajor change in perception that gives performance-baseddesign considerations a greaterimportance in the decisionmaking process fordesign and construction of critical facilities.The performance-based design approach isnot proposed as an immediate substitute fordesign to traditional codes. Rather, it is seenas an opportunity for enhancing and tailoringthe design to match the objectives of thecommunity.FEMA recently funded the developmentof next-generation, performance-basedseismic design guidelines for new andexisting buildings. This process includesdetailed modeling; simulation of buildingresponse to extreme loading; andestimation of potential casualties, loss ofoccupancy, and economic losses. Theprocess allows the design of a buildingto be adjusted to balance the level ofacceptable risks and the cost of achievingthe required level of building performance.Currently the process focuses on seismichazards, but it is general enough to beused with other hazards, as soon as thedevelopment of performance-based designcriteria for wind and other extreme loadsadvances to the point that they can beincorporated into standardized models.1.3.2 Prescriptive Vs. Performance-Based DesignDesign and construction in the United States is generally regulatedby building codes and standards. Building codes typicallyseek to ensure the health, safety, and well-being of people in buildings.Toward this purpose, the building codes and standards setminimum design and construction requirements to address structuralstrength, adequate means of egress for facilities, sanitaryequipment, light and ventilation, and fire safety. Building regulationsmay also promote other objectives, such as energy efficiency,serviceability, quality or value, and accessibility for persons with disabilities.These prescriptive standards are easy to understand andfollow, and easy to monitor. This is their great strength.Historically, building codes were based on a prescriptive approachthat limited the available solutions for compliance, which did notencourage creativity and innovation. Prescriptive or specifica-CRITICAL FACILITY DESIGN CONSIDERATIONS1-15

tion-based design emphasized the “input,” or the materials andmethods required. In contrast, the focus of performance-based designis the “output,” or the expectations and requirements of theusers of a building.Performance-based design requirements define goals and objectivesto be achieved and describe methods that can be used to demonstratewhether buildings meet these goals and objectives. Thisapproach provides a systematic method for assessing the performancecapabilities of a building, system, or component, which canthen be used to verify the equivalent performance of alternatives, deliverstandard performance at a reduced cost, or confirm the higherperformance needed for critical facilities.1.3.3 The Process of Performance-Based Design of CriticalFacilitiesThe performance-based design process explicitly evaluates howbuilding systems are likely to perform under a variety of conditionsassociated with potential hazard events. The process takes into considerationthe uncertainties inherent in quantifying potential risksand assessing the actual responses of building systems and thepotential effects of the performance of these systems on the functionalityof critical facilities. Identifying the performance capabilityof a facility is an integral part of the design process and guides themany design decisions that must be made. Figure 1-4 presents thekey steps in this iterative performance-based design process.Performance-based design starts with selecting design criteria articulatedthrough one or more performance objectives. Eachperformance objective is a statement of the acceptable risk of incurringdifferent levels of damage and the consequential lossesthat occur as a result of this damage. Losses can be associatedwith structural or nonstructural damage, and can be expressed inthe form of casualties, direct economic costs, and loss of servicecosts. Loss of service costs may be the most important loss componentto consider for critical facilities. Acceptable risks are typicallyexpressed as acceptable losses for specific levels of hazard intensityand frequency. They take into consideration all the potentialhazards that could affect the building and the probability of their1-16 CRITICAL FACILITY DESIGN CONSIDERATIONS

occurrence during a specified time period. The overall analysismust consider not only the intensity and frequency of occurrenceof hazard events, but also the effectiveness and reliability of thebuilding systems to survive the event without significant interruptionin the operation of a facility.Figure 1-4:Performance-based design flow diagram(ATC, 2003)NOYES1.3.4 Acceptable Risk andPerformance LevelsPerformance-based design requires a quantitative measure of risk.It also establishes the basis for evaluating acceptable losses and selectingappropriate designs. While specific performance objectivescan vary for each project, the notion of acceptable performancegenerally follows a trend corresponding to:m Little or no damage for small, frequently occurring eventsm Moderate damage for medium-sized, less frequent eventsm Significant damage for very large, very rare eventsCRITICAL FACILITY DESIGN CONSIDERATIONS1-17

Performance objectives should be higher and the correspondingacceptable levels of damage lower for critical facilities and otherimportant buildings than for non-critical facilities. This trend is illustratedin Figure 1-5, taken from the ICC Performance Code forBuildings and Facilities (ICC, 2006). This document defines acceptableperformance for facilities in one of four performancegroups (I, II, III, and IV), using four damage levels (mild, moderate,high, and severe), and given four hazard levels (small,medium, large, and very large). The relative return periods(length of time between occurrences) commonly associated withthe hazard levels for each type of hazard event (seismic, flood, andwind) are indicated in Figure 1-6.Since losses can be associated with structural damage,nonstructural damage, or both, performance objectives mustbe expressed in terms of the potential performance of bothstructural and nonstructural systems. The ICC Performance Codefor Buildings and Facilities has formalized the following four designperformance levels, each of which addresses structuraldamage, nonstructural systems, occupant hazards, overall extentof damage, and release of hazardous materials. Thesedefinitions are general to all hazards and are related to tolerablelimits of impact to the building, its contents, and itsoccupants.Mild Impact: At the mild impact level, the building has no structuraldamage and is safe to occupy. The nonstructural systemsneeded for normal building or facility use and emergencyoperations are fully operational. The number of injured occupantsis minimal, and the nature of the injuries minor. Theoverall extent of the damage is minimal. Minimal amounts ofhazardous materials may be released into the environment.Moderate Impact: At the moderate impact level, structuraldamage is repairable and some delay in re-occupancy canbe expected. The nonstructural systems needed for normalbuilding or facility use and emergency operations are fully operational,although some cleanup and repair may be needed.Injuries to occupants may be locally significant, but generallymoderate in numbers and in nature. There is a low likelihoodof a single life loss and very low likelihood of multiplelife loss. The extent of the damage can be locally significant,1-18 CRITICAL FACILITY DESIGN CONSIDERATIONS

ut is moderate overall. Some hazardous materials may be releasedinto the environment, but the risk to the community isminimal.Figure 1-5: Maximum level of damage to be tolerated (Table 303.3, ICC, 2006b)Note: Performance Group I: Buildings that represent a low hazard to human life in the event of failure. Performance Group II:All buildings except those in Groups I, III, and IV. Performance Group III: Buildings with a substantial hazard to human life inthe event of failure. Group IV: Buildings designed as essential facilities, including emergency operations centers and designateddisaster shelters.Figure 1-6: Relative magnitude and return period for seismic, flood, and wind events (ICC, 2006b)CRITICAL FACILITY DESIGN CONSIDERATIONS1-19

High Impact: At the high impact level, there is significant damageto structural elements, but no falling debris. Significant delaysin reoccupancy can be expected. The nonstructural systemsneeded for normal building use are significantly damaged andinoperable. Emergency systems may be damaged, but remain operational.Injuries to occupants may be locally significant with ahigh risk to life, but are generally moderate in numbers and nature.There is a moderate likelihood of a single life loss, with alow probability of multiple life loss. The extent of damage can begenerally significant and at some locations total. Hazardous materialsare released into the environment, with localized relocationrequired in the immediate vicinity.Severe Impact: At the severe impact level, there is substantial structuraldamage. Repair may not be technically possible. The buildingis not safe for re-occupancy due to the potential for collapse. Thenonstructural systems for normal use and emergency systems maybe nonfunctional. Injuries to occupants may be high in numberand significant in nature. Significant risk to life may exist. Thereis a high likelihood of single life loss and a moderate likelihoodof multiple life loss. Overall damage is substantial. Significantamounts of hazardous materials may be released into the environment,with relocation needed beyond the immediate vicinity.Once the preliminary design has been developed, a series ofsimulations (analyses of building response to loading) areperformed to estimate the probable performance of the buildingunder various design scenario events. Using fragility relationships(vulnerability functions defining the relationship betweenload and damage) developed through testing or calculation,building responses are equated to damage states expressed aslevels of performance. If the simulated performance meets orexceeds the performance objectives, the design is completed.If not, the design must be revised in an iterative process untilthe performance objectives are met. In some cases it will notbe possible to meet the stated objective at a reasonable cost, inwhich case the team of decisionmakers may elect to relax some ofthe original performance objectives.Continued and uninterrupted operation is the most importantperformance requirement of any critical facility, regardless of thelevel of structural and nonstructural building damage. In other1-20 CRITICAL FACILITY DESIGN CONSIDERATIONS

words, the acceptable performance of a critical facility is achievedas long as the structural and nonstructural damage to thebuilding does not disrupt or impair the continued operation ofthat facility. In recent hurricanes, however, undamaged structureswere frequently rendered inoperable as a result of nonstructuraldamage resulting in unacceptable performance (FEMA, 2006).In terms of affecting the ability of a facility to function, the failureof nonstructural systems (roofing; exterior envelope; heating, ventillating,and air conditioning [HVAC]; emergency systems) can beas significant as the failure of structural components. Performancebaseddesign provides a framework for considering the potentialhazards that can affect a facility or site, and for explicitly evaluatingthe performance capability of the facility and its components.Consideration must also be given to the likely possibility that atleast a portion of the distribution systems for critical infrastructureservices (e.g., electrical power, communications, potablewater, and sanitary sewer) could be interrupted. The impact ofsuch an interruption in service should be assessed for the facility,along with an estimate of the time it would take until servicecould be restored or supplemented. For protecting the continuedoperation of critical facilities, the most reliable approach is toprovide alternative onsite sources for critical infrastructure needsin the form of: (1) emergency power generation capabilities; (2)local wireless communications; (3) potable water supplies; and(4) temporary onsite storage for sanitary waste.While the practice of performance-based design is currentlymore advanced in the field of seismic design than the fields offlood and high-wind design, the theory of performance-baseddesign is completely transferable to all hazards. The practice ofperformance-based design will prompt designers and owners ofbuildings in flood- or high-wind-prone regions to begin thinkingin terms of a few basic objectives:m Can the real probabilities and frequencies of high-wind andflood events during the useful life of the building be definedwith an acceptable degree of accuracy?m Can the extent and kinds of damage that can be tolerated bedefined?CRITICAL FACILITY DESIGN CONSIDERATIONS1-21

m Are there ways in which an acceptable level of performancecan be achieved?m Are there alternative levels of performance that can beachieved, and how much do they cost over the lifetime/ownership of the building compared to the benefits ofreduced damage and improved performance?m How do these levels compare to the performance levels ofdesigns using the minimum requirements of the applicablebuilding code?1.3.5 Performance-Based FloodDesignThe performance levels and objectives for flood hazards, first outlinedin FEMA 424 (2004), have been expanded and generalizedfor performance-based flood design of critical facilities as follows:Level 1 (Operational): The facility sustains no structural ornonstructural damage, emergency operations are fully functional,and the building can be immediately operational. The site is notaffected by erosion, but may have minor debris and sedimentdeposits.Level 2 (Moderate Impact): The facility is affected by flooding abovethe lowest floor, but damage is minimal due to low depths andshort duration of flooding. Cleanup, drying, and minor repairs arerequired, especially of surface materials and affected equipment,but the building can be back in service in a short period of time.Level 3 (High Impact): The facility may sustain structural ornonstructural damage that requires repair or partial reconstruction,but the threat to life is minimal and occupant injuries shouldbe few and minor. Water damage to the interior of the facility requirescleanup, drying, and repairs, and can prohibit occupancy ofall or a portion of the facility for several weeks to several months.Level 4 (Severe Impact): The facility is severely damaged and likelyrequires demolition or extensive structural repair. Threats to occupantsare substantial, and warning plans should prompt evacuation1-22 CRITICAL FACILITY DESIGN CONSIDERATIONS

prior to the onset of this level of flooding. Level 4 is applicable tofacilities affected by all types of flooding, including those that resultfrom failure of dams, levees, or floodwalls.Planning and design to achieve an appropriate level of flood protectionfor critical facilities should include avoidance of floodhazard areas and adding a factor of safety (freeboard) to theanticipated flood elevation. Performance evaluation of a facilityaffected by flooding needs to include consideration of thebuilding response to the following load conditions (fragility functionsmust be developed to relate calculated response to actualdamage states):m Lateral hydrostatic forcesm Vertical (buoyant) hydrostatic forcesm Hydrodynamic forcesm Surge forcesm Impact forces of flood-borne debrism Breaking wave forcesm Localized scour1.3.6 Performance-Based High-WindDesignThe performance objectives for wind hazards, outlined in FEMA424, have been expanded and generalized for performance-basedflood design of critical facilities as follows:Level 1 (Operational): The facility is essentially undamaged and canbe immediately operational.Level 2 (Moderate Impact): The facility is damaged and needs somerepairs, but can remain occupied and be functional after minorrepairs to nonstructural components are complete.CRITICAL FACILITY DESIGN CONSIDERATIONS1-23

Level 3 (High Impact): The facility may be structurally damagedbut the threat to life is minimal and occupant injuries should befew and minor. However, damage to nonstructural components(e.g., roofing, building envelope, exterior-mounted equipment)is great, and the cost to repair the damage is significant. If rain accompaniesthe windstorm, or if rain occurs prior to execution ofemergency repairs, water damage to the interior of the facility canprohibit occupancy of all or a portion of the facility for severalweeks to several months.Level 4 (Severe Impact): The facility is severely damaged and willprobably need to be demolished. Significant collapse may haveoccurred, and there is a great likelihood of occupant casualtiesunless the facility has a specially designed occupant shelter. Level4 is applicable to facilities struck by strong or violent hurricanes ortornadoes. For other types of windstorms, Level 4 should not bereached.The challenge with respect to performance-based high-wind designis assessing the wind resistance of the building envelope andexterior-mounted equipment, and the corresponding damage susceptibility.This is challenging because of several factors:m Analytical tools (i.e., calculations) are currently not availablefor many envelope systems and components, and there is alack of realistic long-term wind resistance data.m Because of the complexity of their wind load response, manyenvelope systems and components require laboratory testing,rather than analytical evaluation, in order to determine theirload-carrying capacity.m It is likely that finite element analysis will eventually augmentor replace laboratory testing, but substantial research isnecessary before finite element analysis becomes available forthe broad range of existing building envelope systems.m Before performance-based design for high winds can becomea reality, a solid research base on the response of buildings andcomponents to the effects of high winds must be established.1-24 CRITICAL FACILITY DESIGN CONSIDERATIONS

1.4 REFERENCESAmerican Society of Civil Engineers, Structural EngineeringInstitute, Minimum Design Loads for Buildings and Other Structures,ASCE/SEI 7-05, Reston, VA, 2006.Applied Technology Council, Proceedings of FEMA-SponsoredWorkshop on Performance-Based Seismic Design, ATC-58-3 Report,Redwood City, CA, 2003.Applied Technology Council, prepared for the Building SeismicSafety Council, NEHRP Guidelines for the Seismic Rehabilitation ofBuildings, funded and published by FEMA (FEMA 273 Report),Washington, DC, 1997.Executive Order of the President, Floodplain Management,11988, 42 FR 26951, 3 CFR, p117, Washington, DC, 1977.Federal Emergency Management Agency, Design Guide forImproving School Safety in Earthquakes, Floods, and High Winds, FEMA424, Washington, DC, 2004.Federal Emergency Management Agency, Summary Report onBuilding Performance, Hurricane Katrina 2005, FEMA 549 Report,Washington, DC, 2006.National Fire Protection Association, 101 Life Safety Code, Quincy,MA, 2006a.CRITICAL FACILITY DESIGN CONSIDERATIONS1-25

National Fire Protection Association, NFPA 5000 BuildingConstruction and Safety Code, Quincy, MA, 2006b.International Code Council, Inc., International Code CouncilPerformance Code for Buildings and Facilities, Falls Church, VA, 2006.Structural Engineers Association of California, Performance-BasedSeismic Engineering of Buildings, Vision 2000 Report, Sacramento,CA, 1995.1-26 CRITICAL FACILITY DESIGN CONSIDERATIONS

MAKING CRITICAL FACILITIES SAFE FROM Flooding 22.1 GENERAL DESIGN CONSIDERATIONSThis chapter introduces the physical nature and mechanicsof floods and explains how flood probabilities aredetermined and how flood hazard areas are identified. Itdescribes the types of flood damage that can result when criticalfacilities are located in flood hazard areas or are affected by flooding.A series of requirements and best practices are introducedthat facility owners, planners, and designers should consider forreducing the risks from flooding to new critical facilities and toexisting facilities already located in areas prone to flooding.This chapter demonstrates why avoidance of flood hazard areasis the most effective way to minimize the life-safety risk to the occupantsand general public who rely on these facilities, as well asto minimize the potential for damage to buildings and other elementsof critical facilities. When an existing facility is exposed toflooding, or if a new facility is proposed for a flood hazard area,steps need to be taken to minimize the risks. A well-planned, designed,constructed, and maintained critical facility should be ableto withstand damage and remain functional after a flooding event,even one of low probability.2.1.1 NATURE AND CHARACTERISTICS OFFLOODINGFlooding is the most common natural hazard in the United States,affecting more than 20,000 local jurisdictions and representingmore than 70 percent of Presidential disaster declarations. SeveralMAKING CRITICAL FACILITIES SAFE FROM Flooding2-

evaluations have estimated that 7 to 10 percent of the Nation’sland area is subject to flooding. Some communities have very littleflood risk; others lie entirely within a floodplain.Flooding is a natural process that may occur in a variety of forms:long-duration flooding along rivers that drain large watersheds;flash floods that send a devastating wall of water down a mountaincanyon; and coastal flooding that accompanies high tides andonshore winds, hurricanes, and nor’easters. When the naturalprocess does not affect human activity, flooding is not a problem.In fact, many species of plants and animals that live adjacent tobodies of water are adapted to a regimen of periodic flooding.Flooding is only considered a problem when human developmentis located in flood-prone areas. Such development exposes peopleto potentially life threatening situations and makes property vulnerableto serious damage or destruction. It also can disrupt thenatural surface flow, redirecting water onto lands not normallysubject to flooding.Flooding along waterways normally occurs as a result of excessiverainfall or snowmelt that creates water flows exceeding the capacityof channels. Flooding along shorelines is usually a result ofcoastal storms that generate storm surges or waves above normaltidal fluctuations. Factors that can affect the frequency and severityof flooding and the resulting damage include:m Channel obstructions caused by fallen trees, accumulateddebris, and ice jamsm Channel obstructions caused by road and rail crossings wherethe bridge or culvert openings are insufficient to conveyfloodwatersm Erosion of shorelines and stream banks, often with episodiccollapse of large areas of landm Deposition of sediment that settles out of floodwaters or iscarried inland by wave actionm Increased upland development of impervious surfaces andmanmade drainage improvements that increase runoff volumes2- MAKING CRITICAL FACILITIES SAFE FROM Flooding

m Land subsidence, which increases flood depthsm Failure of dams (resulting from seismic activity, lack of maintenance,flows that exceed the design, or destructive acts), whichmay suddenly and unexpectedly release large volumes of waterm Failure of levees (associated with flows that exceed thedesign, weakening by seismic activity, lack of maintenance, ordestructive acts), which may result in sudden flooding of areasbehind leveesEach type of flooding has characteristics that represent importantaspects of the hazard. These characteristics should be consideredin the selection of critical facility sites, the design of new facilities,and the expansion or rehabilitation of existing flood-pronefacilities.Riverine flooding results from the accumulation of runoff fromrainfall or snowmelt, such that the volume of flow exceeds thecapacity of waterway channels and spreads out over the adjacentland. Riverine flooding flows downstream under the forceof gravity. Its depth, duration, and velocity are functions of manyfactors, including watershed size and slope, degree of upstreamdevelopment, soil types and nature of vegetation, topography,and characteristics of storms (or depth of snowpack and rate ofmelting). Figure 2-1 illustrates a cross-section of the generic riverinefloodplain.Flood Hazard Area(100-Year Floodplain)Figure 2-1:The riverine floodplainFringeFloodway*StreamChannelFringeFloodLevel* Floodway is defined in Section 2.1.1.2Normal WaterLevelMAKING CRITICAL FACILITIES SAFE FROM Flooding2-

Coastal flooding is experienced along the Atlantic, Gulf, andPacific coasts, and many larger lakes, including the GreatLakes. Coastal flooding is influenced by storm surges associatedwith tropical cyclonic weather systems (hurricanes, tropicalstorms, tropical depressions, typhoons), extratropical systems(nor’easters), and tsunamis (surge induced by seismic activity).Coastal flooding can also be characterized by wind-driven waves,which also affect reaches along the Great Lakes shorelines; windsblowing across the broad expanses of water generate waves thatcan rival those experienced along ocean shorelines. Some GreatLakes shorelines experience coastal erosion, in part because theerosion is associated with fluctuations in water levels. Figure 2-2 isa schematic of the generic coastal floodplain.A number of factors associated with riverine and coastal flooding areimportant in the selection of sites for critical facilities, in site design,and in the architectural and engineering design of critical facilities.Depth: The most obvious characteristic of any flood is the depth ofthe water. Depending on many factors, such as the shape of a river* * ** Zones are defined in Section 2.1.1.2Figure 2-2: The floodplain along an open coast2- MAKING CRITICAL FACILITIES SAFE FROM Flooding

valley or the presence of obstructing bridges, riverine floodingmay rise just a few feet or tens of feet above normal levels. Thedepth of coastal flooding is influenced by such factors as the tidalcycle, the duration of the storm, the elevation of the land, andthe presence of waves. Depth is a critical factor in building design,because the hydrostatic forces on a vertical surface (such asa foundation wall) are directly related to depth, and because costsassociated with protecting buildings from flooding increase withdepth. Under certain conditions, hurricanes can produce stormsurge flooding that is 20 to 30 feet above mean sea level or, in extremecases such as reported during Hurricane Katrina, as muchas 35 feet above mean sea level.Duration: Duration is the measure of how long the water remainsabove normal levels. The duration of riverine flooding is primarilya function of watershed size and the longitudinal slope ofthe valley (which influences how fast water drains away). Smallwatersheds are more likely to be “flashy,” which refers to the rapiditywith which floodwaters rise and fall. Areas adjacent to largerivers may be flooded for weeks or months. Most coastal floodingis influenced by the normal tidal cycle, as well as how fast coastalstorms move through the region. Areas subject to coastal floodingcan experience long duration flooding where drainage is pooror slow as a result of topography or the presence of flood controlstructures. For example, there may be depressionsin the land that would hold water,or water may be trapped behind a floodwallor levee with inadequate drainage. Morecommonly, coastal flooding is of shorterduration, on the order of 12 to 24 hours, especiallyif storms move rapidly. Floodingalong large lakes, including those behinddams, can be of very long duration becausethe large volume of water takes longer todrain. For building design, duration is importantbecause it affects access, buildingusability, and saturation and stability of soilsand building materials. Information aboutflood duration is sometimes available as partof a flood study, or could be developed by aqualified engineer.Local drainage problems create pondingand local flooding that often is not directlyassociated with a body of water such asa creek or river. Although such flooding isrelatively shallow and not characterizedby high velocity flows, considerabledamage may result. Areas with poordrainage frequently experience repetitivedamage. Some local drainage problemsare exacerbated by old or undersizeddrainage system infrastructure. Floodingcaused by drainage problems typicallyoccurs as sheetflow or along waterwayswith small drainage areas. This type offlooding is often not mapped or regulated.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-

Velocity: The velocity of floodwaters ranges from extremely high(associated with flash floods or storm surge) to very low or nearlystagnant (in backwater areas and expansive floodplains). Velocityis important in site planning because of the potential for erosion.In structural design, velocity is a factor in determining the hydrodynamicloads and impact loads. Even shallow, high-velocitywater can threaten the lives of pedestrians and motorists. Accurateestimates of velocities are difficult to make, although velocity informationmay be found in some floodplain studies.Wave action: Waves contribute to erosion and scour (see Figure2-2), and also contribute significantly to design loads on buildings.The magnitude of wave forces can be 10 to more than 100times greater than wind and other design loads, and thus may controlmany design parameters. Waves must be accounted for insite planning along coastal shorelines, in flood hazard areas thatare inland of open coasts, and other areas where waves occur, includingareas with sufficient fetch that winds can generate waves(such as lakes and expansive riverine floodplains). Waves on topof storm surges may be as much as 50 percent higher than thedepth of the surge.Impacts from debris and ice: Floating debris and ice contribute tothe loads that must be accounted for in structure design. Themethods and models used to predict and delineate flood hazardareas do not specifically incorporate debris loads. Thus, there arefew sources to determine the potential effects of debris impact,other than past observations and judgment.Erosion and scour: Erosion is the lowering of the ground surface asa result of a flood event, or the gradual recession of a shoreline asa result of long-term coastal processes. Scour refers to a localizedlowering of the ground surface due to the interaction of currentsand/or waves with structural elements, such as pilings. Soil characteristicsinfluence an area’s susceptibility to scour. Erosion andscour may affect the stability of foundations and filled areas, andmay cause extensive site damage.2- MAKING CRITICAL FACILITIES SAFE FROM Flooding

2.1.1.1 Probability of Occurrence or FrequencyThe probability of occurrence, or frequency, is a statement of thelikelihood that an event of a certain magnitude will occur in agiven period of time. For many decades, floodplain managementhas been based on the flood that has a 1 percent chance of occurringin any given year, commonly called the “100-year flood.”For certain critical actions and decisions,such as planning or constructing a critical facility,the basis of risk decisions should be theflood that has a 0.2 percent probability of occurringin any given year, commonly calledthe “500-year flood.”The term “100-year flood” as an expressionof probability or frequency is often misunderstoodbecause it conveys the impressionthat a flood of that magnitude will occur onlyonce every 100 years. Actually, the 1-percentannual-chanceflood has one chance in 100of occurring in any given year. The fact thata 1-percent-annual-chance flood is experienced at a specific locationdoes not alter the probability that a comparable flood couldoccur at the same location in the next year, or even multiple timesin a single year. As the length of the period increases, so does theprobability that a flood of a specific magnitude or greater willoccur. For example, during a 30-year period (the usual lending periodfor a home mortgage), the probability that a 100-year floodwill occur is 26 percent. And during a 70-year period (the potentialuseful life of many buildings), the probability increases to 50percent. Similarly, the 500-year flood has a 0.2-percent probabilityof being equaled or exceeded in any given year, and during a 70-year period the probability of occurrence is 18 percent.Regardless of the flood selected for design purposes (the“design flood”), the designer must determine specific characteristicsassociated with that flood. Determining a flood with aspecific probability of occurrence is done in a multi-step processthat typically involves using computer models that are inthe public domain. If a sufficiently long record of flood informationexists, the design flood may be determined by applyingstatistical tools to the data. Alternatively, water resource engi-The assigned frequency of a flood (e.g.,100-year) is independent of the numberof years between actual occurrences.Hurricane Camille hit the Mississippi coastin 1969 with storm surge flooding that farexceeded previous events, and HurricaneKatrina affected much the same area.Although just 36 years apart, both stormsproduced flood levels significantly higherthan the 100-year flood.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-

Flood frequency analyses are performedusing historical records, and the resultsare influenced by the length of therecord. Such analyses do not accountfor recent changes to the land (uplanddevelopment or subsidence) or futurechanges (additional development, greatersubsidence, or climatic variations).neers sometimes apply computer models tosimulate different rainfall events over watersheds,to predict how much water will runoff and accumulate in channels. Other computermodels are used to characterize theflow of water down the watershed and predicthow high the floodwaters will rise.For coastal areas, both historical stormsand simulated storm surge models canbe used to predict the probability thatfloodwaters will rise to a certain level and be accompaniedby waves of certain heights. Many coastal storms will producestorm surge flooding that, depending on local topography,may extend inland significantly farther than anticipated forthe 1-percent-annual-chance flood. Statistically, such extremestorm surges occur less frequently than the 1-percent or 0.2-percent-annual-chance floods, but their consequences can becatastrophic.Planners and designers should research the relationshipbetween the flood levels for different frequency events and extremeevents, especially in hurricane-prone communities. Thedifference in flood levels may be extreme in some situations,depending on local conditions and the source of flooding. Inother areas the lower probability flood depths might not bemuch higher than the 1-percent-annual-chance flood.The National Flood Insurance Program (NFIP) is a Federalprogram that encourages communities to regulate floodhazard areas and, in return, offers property owners insuranceprotection against losses from flooding (see Sections 2.1.3.1and 2.1.3.2). The NFIP uses the 1-percent-annual-chance floodas the basis for flood hazard maps, for setting insurance rates,and for application of regulations in order to minimize futureflood damage. The 1-percent-annual-chance flood is also usedas the standard for examination of older buildings to determinethe measures to apply in order to reduce future damage.Satisfying the minimum requirements of the NFIP does notprovide adequate protection for critical facilities that need tobe functional even after low probability events. Nearly every2- MAKING CRITICAL FACILITIES SAFE FROM Flooding

year, a very low probability flood occurssomewhere in the United States, often with The Saffir-Simpson Hurricane Scalecatastrophic consequences. Therefore, for categorizes hurricanes based on sustainedplanning and design of critical facilities, wind speeds (see Section 3.1.1). Stormuse of a lower probability flood (at leastsurge is not always correlated with thethe 500-year) is strongly recommended.category because other factors influenceAs noted in Section 2.1.3.3, the 500-year surge elevations, notably forward speed oflevel of protection is required if Federal the storm, tide cycle, offshore bathymetry,funds are involved in constructing facilities and land topography.that are vital for emergency response andrapid recovery, including hospitals, EOCs,emergency shelters, and other buildings that support vital services.This reinforces the importance of protecting both thefunctionality and financial investment in a critical facility withstricter standards than those applied to other buildings.2.1.1.2 Hazard Identification and Flood DataFlood hazard maps identify areas of the landscape that are subjectto flooding, usually flooding by the 1-percent-annual-chanceflood. Maps prepared by the NFIP are the minimum basis ofState and local floodplain regulatory programs. Some Statesand communities have prepared maps of a floodplain based onthe assumption that the upper watershed area is fully developedaccording to existing zoning. Some communities base their regulationson a flood of record or a historically significant flood thatexceeds the base flood shown on the NFIP maps.The flood hazard maps used by the appropriate regulatory authorityshould be consulted during planning and site selection,site design, and architectural and engineering design (whetherfor the design of new buildings or rehabilitation of existingbuildings). Regardless of the flood hazard data required for regulatorypurposes, additional research should be conducted onpast major floods and other factors that could lead to more severeflooding.The NFIP produces Flood Insurance Rate Maps (FIRMs) for morethan 20,000 communities nationwide. FIRMs are prepared for eachlocal jurisdiction that has been determined to have some degreeof flood risk. The current effective maps are typically available forMAKING CRITICAL FACILITIES SAFE FROM Flooding2-

It is important to note that the number ofrevised and updated FIRMs is increasingrapidly. During the last few years FEMA,in partnership with many States andcommunities, has been implementingan initiative to modernize and updateall maps that are determined to be outof date. The modernization processmay involve an examination of floodexperience in the period since the originalflood studies were prepared, use of moredetailed topography and base maps, recomputationof flood discharges and floodheights, and re-delineation of flood hazardarea boundaries.viewing in community planning or permitoffices. 1 It is important to use the most recentflood hazard map when determiningsite-specific flood hazard characteristics. Althoughmany FIRMs are more than 15 yearsold, often one or more panels or portions ofa map panel have been revised and republished.Communities must adopt revised mapsto continue participating in the NFIP.Some FIRMs do not show the 0.2-percentannual-chanceflood hazard area (500-yearfloodplain), and many FIRMs do not providedetailed information about predictedflood elevations along every body of water,especially smaller streams and tributaries. Determiningthe 500-year flood is especiallydifficult when records of past flood events arelimited. When existing data are insufficient, additional statisticalmethods and engineering analyses are necessary to determine theflood-prone areas and the appropriate characteristics of floodingrequired for site layout and building design.If a proposed facility site or existing facility is affected byflooding, a site-specific topographic survey is critical to delineatethe land that is below the flood elevation used for planning purposes.If detailed flood elevation information is not available, afloodplain study may be required to identify the important floodcharacteristics and data required for sound design. Having floodhazard areas delineated on a map conveys a degree of precisionthat may be misleading. Flood maps have a number of limitationsthat should be taken into consideration, especially during site selectionand design of critical facilities. Some of the well-knownlimitations are:m Flood hazard areas are approximations based on probabilities;the flood elevations shown and the areas delineated shouldnot be taken as absolutes, in part because they are based onnumerical approximations of the real world.1. Flood maps may also be viewed at FEMA’s Map Store at http://www.fema.gov. For a fee, copies may be ordered online or by calling(800) 358-9616. The Flood Insurance Study (FIS) and engineering analyses used to determine the flood hazard area may be ordered throughthe FEMA Web site.2-10 MAKING CRITICAL FACILITIES SAFE FROM Flooding

m FIRMs and Flood Insurance Studies(FISs) are prepared to meet therequirements of the NFIP. For the mostpart, floodplains along smaller streamsand drainage areas (less than 1 squaremile) are not shown.m Especially for older maps, the topographyused to delineate the flood boundary mayhave had contour intervals of 5, 10, oreven 20 feet, which significantly affectsthe precision with which the boundaryis determined. The actual elevation ofthe ground relative to the flood elevationis critical, as opposed to whether an areais shown as being in or out of the mappedflood hazard area.In communities along the Gulf and Atlanticcoasts, facility owners, planners, anddesigners should check with emergencymanagement offices for maps that estimatestorm surge flooding from hurricanes.Local planning or engineering offices mayhave post-disaster advisory flood mapsand documentation of past storm surgeevents. The FIRMs and regulatory designflood elevations (DFEs) do not reflect lowprobability/high magnitude floodingthat may result from a hurricane makinglandfall at a specific location.m Maps are based on the data available at the time they wereprepared, and therefore do not account for subsequentupland development (new development that increases rainfallrunofftends to increase flooding).m The scale of the maps may impedeprecise determinations (many older mapsare 1 inch = 2,000 feet).m Flooding characteristics may have beenaltered by development, sometimes byupland development that has increasedrunoff, and other times by localmodifications that have altered the shapeof the land surface of the floodplain(such as fills or levees).m Local conditions are not reflected,especially conditions that changeregularly, such as stream bank erosionand shoreline erosion.m Areas exposed to very low probabilityflooding are not shown, such as floodingDesigners and property owners in coastalregions should be aware that current FIRMsmay not fully account for natural andmanmade changes to beaches, wetlands,and other coastal environments (e.g., theerosion of protective dunes during thebase flood). Since the original FIRMswere published in the early 1980s, FEMAhas made significant improvements inthe models and methods used to identifycoastal flood hazards. Before any actionis considered, the Flood Insurance Studyreport should be checked to verify that allpertinent hazards have been addressed.A coastal engineer or similar professionalshould be consulted if there are anyquestions concerning the coastal flood data.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-11

“Base flood elevation” is the elevationabove a datum to which floodwaters arepredicted to rise during the 1-percentannual-chanceflood (also called the “baseflood” or the 100-year flood).from extreme hurricane storm surges, extreme riverineflooding, dam failures, or overtopping or failure of levees.The flood hazard maps prepared by the NFIP show different floodzones to delineate different floodplain characteristics (see Figures2-3 and 2-4). The flood zones shown on the NFIP maps, and someother designations, are as described below.A Zones: (also called “unnumbered A Zones” or “approximate AZones”). This designation is used for flood hazard areas whereengineering analyses have not been performed to developdetailed flood elevations. Base flood elevations(BFEs) are not provided. Additionalengineering analyses and site-specific assessmentsusually are required to determine thedesign flood elevation.AE Zones or A1-A30 Zones: (also called “numberedA Zones”). These designations areused for flood hazard areas where engineeringanalyses have produced detailed flood elevations andboundaries for the base flood (1-percent-annual-chance flood).BFEs are provided. For riverine waterways with these zones, FISsinclude longitudinal profiles showing water surface elevations fordifferent frequency flood events.Floodways: The floodway includes the waterway channel and adjacentland areas that must be reserved in order to convey thedischarge of the base flood without cumulatively increasing thewater surface elevation above a designated height. Floodwaysare designated for most waterways that have AE Zones or numberedA Zones. FISs include data on floodway widths and meanfloodway velocities.AO and AH Zones: These zones include areas of shallow floodingand are generally shown where the flood depth averages from 1 to3 feet, where a clearly defined channel does not exist, where thepath of flooding is unpredictable, and where velocity flow may beevident. These zones are characterized by ponding or sheetflow.BFEs may be provided for AH Zones; flood depths may be specifiedin AO Zones.2-12 MAKING CRITICAL FACILITIES SAFE FROM Flooding

Figure 2-3: Riverine flood hazard zonesFigure 2-4: Coastal flood hazard areasMAKING CRITICAL FACILITIES SAFE FROM Flooding2-13

Coastal A Zone: The current editions of themodel building codes refer to ASCE 7 andASCE 24, which are two design standardsthat include requirements for CoastalA Zones that account for the increasedrisk from the additional wave height (seeSection 2.3.2).Shaded X (or B) Zones: This zone shows areas of the 500-year flood(0.2-percent-annual-chance flood), or areas protected by floodcontrol levees. This zone is not shown on many NFIP maps; its absencedoes not imply that flooding of this frequency will not occur.Unshaded X (or C) Zones: These zones are all land areas not mappedas flood hazard areas that are outside of the floodplain and designatedfor the purposes of regulating development pursuant tothe NFIP. These zones may still be subject to small stream floodingand flooding from local drainage problems.V Zones (V, VE, and V1-V30): Also known as coastal high-hazardareas or special flood hazard areas subject to high-velocity wave action.V Zones are relatively narrow areas along open coastlines andsome large lake shores that are subject to high-velocity wave actionfrom storms or seismic sources. V Zones extend from offshoreto the inland limit of a primary frontal dune, or to an inland limitwhere the height of breaking waves drops below 3 feet.Coastal A Zone: This zone, which is not delineated on NFIP maps,is where the potential of breaking wave heights is between 1.5feet and 3 feet during base flood conditions. Coastal A Zonesare landward of the mapped V Zone, or landward of open coaststhat do not have a V Zone because breakingwaves are predicted to be less than 3 feethigh. In these areas, the principal sources offlooding are tides, storm surges, seiches, ortsunamis, not riverine flooding.Flood hazards and characteristics of floodingmust be identified to evaluate appropriatelythe impact of site development, to calculateflood loads, to design floodproofing measures,and to identify and prioritize retrofitmeasures for existing critical facilities. Table 2-3 in Section 2.5 outlinesa series of questions to facilitate this objective.Many characteristics of flooding are not shown on the FIRMs butmay be found in the FIS or the study or report prepared by the entitythat produced the flood hazard map. Hurricane storm surgeinundation maps based on the National Hurricane Center models2-14 MAKING CRITICAL FACILITIES SAFE FROM Flooding

have been prepared by the U.S. Army Corpsof Engineers for most reaches of the Atlantic Hurricanes can produce storm surgeand Gulf coasts. The maps combine the resultsof many scenarios to show the maximum than the BFE shown on the FIRMs.flooding and waves that rise much higherpotential surge inundation associated withdifferent categories of hurricanes. State andlocal emergency management offices use the maps for evacuationplanning.2.1.1.3 Design Flood ElevationThe DFE establishes the minimum level of flood protection thatmust be provided. The DFE, as used in the model building codes,is defined as either the BFE determined by the NFIP and shown onFIRMs, or the elevation of a design flood designated by the community,whichever is higher. The DFE will always be at least as highas the BFE. Communities may use a design flood that is higherthan the base flood for a number of reasons.For example, a design flood may be used toaccount for future upland development, torecognize a historic flood, or to incorporate afactor of safety, known as freeboard.Facility owners, planners, and designersshould check with the appropriate regulatoryauthority to determine the minimumflood elevation to be used in site planningand design. Although the NFIP minimumis the BFE, State or local regulations commonlycite the 0.2-percent-annual-chance flood (500-year flood)as the design requirement for critical facilities, or the regulationsmay call for added freeboard above the minimum flood elevation.Even if there is no specific requirement to use the 0.2-percent-annual-chanceflood for siting and design purposes, it is stronglyrecommended that decisionmakers take into consideration theflood conditions associated with this lower probability event orfrom other floods of record.“Freeboard” is a factor of safety usuallyexpressed in feet above a flood level. Freeboardcompensates for the many unknownfactors that could contribute to floodheights, such as wave action, constrictingbridge openings, and the hydrologicaleffect of urbanization of the watershed. Afreeboard from 1 to 3 feet is often appliedto critical facilities.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-15

2.1.1.4 Advisory Base Flood ElevationThe flood maps and flood hazard data described in Section 2.1.1.2are the minimum information required to be used for regulatorypurposes. The updating of FIRMs is a continuous process andit relies heavily on examination of storm event data and physicalchanges to the landscape. If significant flood events have occurredsince the effective date of the FIRM, these events may change thestatistical analyses, which would then prompt an update of theflood maps and produce revised elevations for the 1-percent-annual-chanceflood. Critical facility owners, planners, and designersshould contact community officials to determine whether therehave been any significant flood events or other changes that mayaffect flood hazards since the effective date of the FIRM. The bestavailable information should be used at all times.FEMA works closely with communities to develop new floodhazard data or revise existing data during the standard flood studyprocess. Updating flood hazard data includes the analysis of historicaldata. If a major flood event significantly alters the physicalenvironment or if it is determined to be statistically significant,FEMA may decide to release Advisory BFEs (ABFEs) and FloodRecovery Maps (see Figure 2-5).Figure 2-5: Example of a flood recovery map showing ABFEs and other flood hazard information.2-16 MAKING CRITICAL FACILITIES SAFE FROM Flooding

ABFEs represent the best estimate of theexpected 1-percent-annual-chance flood elevations.They are provided as interim floodhazard information until more detailed floodhazard data become available. Flood RecoveryMaps depict the ABFEs, and in general,reflect additional information such as inundationlimits and surveyed high water marks (but not the 500-yearflood hazard area). For coastal areas, the Flood Recovery Maps mayalso show the inland debris line and the limit of the 1.5-foot wave(Coastal A Zone).When ABFEs and Flood Recovery Maps are produced and released,FEMA strongly encourages States and communities, aswell as private property owners and critical facility owners, to usethe information to make decisions about reconstruction untilmore definitive data become available. FEMA issues guidance tohelp the users apply the updated flood elevation information atspecific locations.After Flood Recovery Maps are released, FEMA begins the formalprocess of updating the FIRMs. The community and propertyowners are notified through public notices and meetings whenthe preliminary revised maps are available and a formal commentperiod is opened. The final maps are prepared after considerationof comments. Communities are required to adopt and use the revisedFIRMs in order to continue their participation in the NFIP.After Hurricane Katrina, FEMA expediteddevelopment of Flood Recovery Maps andABFEs for the Mississippi coast—the newmaps were delivered just 3 months afterthe storm.2.1.2 FLOOD LOADSFloodwaters can impose a variety of loads on buildings andbuilding elements. This section provides a brief overview of floodloads and factors that are important for calculating flood loads,including:m Hydrostatic loads, including buoyancy, which increase as thedepth of water increasesm Hydrodynamic loads, which result from moving waterMAKING CRITICAL FACILITIES SAFE FROM Flooding2-17

m Breaking wave loads, which are most likely to occur in coastalareasm Impact loads resulting from floating debris striking a buildingor building elementm Long-term erosion and localized scour, which can increase theeffects and magnitudes of other loads2.1.2.1 Design Flood DepthWater depth associated with the design flood is computed by determiningthe DFE (see Section 2.1.1.3 or 2.1.1.4) and subtractingthe elevation of the ground at the building site. Since theseelevation data usually are obtained from different sources, it is importantto determine whether they are based on the same datum.If not, standard corrections must be applied.Flood depth is the most important factor required to computeflood loads, because almost every other flood load calculation dependsdirectly or indirectly on this factor. In riverine areas, theflood depth rarely accounts for waves. In coastal areas, the totalflood depth is composed of a “stillwater” depth, plus the expectedheight of waves (see Figure 2-6).Figure 2-6:Definition sketch—waveheight and stillwater depth2-18 MAKING CRITICAL FACILITIES SAFE FROM Flooding

The following characteristics that may add to the flood depthshould be taken into consideration.Small waves: In Coastal A Zones (see Section2.3.2), the DFE shown on FEMA’s maps does Waves and storm-induced erosion are mostnot include the wave height. Coastal A Zones common in coastal areas. However, wideare characterized by 1.5- to 3-foot high waves. rivers and lakes may experience winddrivenwaves and erodible soils are foundThe flood depth should be increased by 3 feetfor sites close to the V Zone boundary or the throughout the United States. For moreshoreline. For sites farther inland, where the information about waves and erosion, referflood depth is at least 3 feet, it should be increasedby 1.5 feet. Interpolation may be usedto FEMA 55, Coastal Construction Manual.to determine the amount that should be addedto the flood depth to account for waves in the Coastal A Zone.Erosion and scour: Flood depths in areas with erodible soils shouldconsider the effects of erosion where floodwaters lower theground surface or cause local scour around foundation elements.In these areas, the flood depth determined using the design floodelevation should be increased to account for changes in conditionsduring a flood event. Not only does lowering the groundsurface effectively result in deeper water against the foundation, itmay also remove supporting soil from the foundation, which mustbe accounted for in the foundation design.2.1.2.2 Design Flood Velocity—RiverineThere are few sources of information that are readily available forestimating design flood velocities at specific locations along riverinebodies of water. If a riverine source has been studied usingdetailed hydraulic methods, some information may be availablein summary form in published studies. Studies prepared for theNFIP (see Section 2.1.1.2) contain tables of data for waterwaysfor which floodways were delineated. For specified cross-sectionsalong the waterway, the Floodway Data Table includes a meanvelocity expressed in feet per second. This value is the averageof all velocities across the floodway. Generally, velocities in theflood fringe (landward of the floodway) will be lower than in thefloodway.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-19

For waterways without detailed studies, methods that are commonlyused in civil engineering for estimating open channel flow velocitiescan be applied.Upper bound velocities caused by HurricaneKatrina along the Mississippi coast,where storm surge depths neared 35 feetdeep, have been estimated at nearly 30feet per second (20 miles per hour).2.1.2.3 Design Flood Velocity—CoastalEstimating design flood velocities in coastal flood hazard areas issubject to considerable uncertainty, and there is little reliable historicalinformation or measurements from actual coastal floodevents. In this context, velocity does not refer to the motion associatedwith breaking waves, but the speed of the mass movement offloodwater over an area.The direction and velocity of floodwaters can vary significantlythroughout a coastal flood event. Floodwaters can approach asite from one direction as a storm approaches, then shift to anotherdirection (or through several directions) as the stormmoves through the area. Floodwaters can inundate some low-lyingcoastal sites from both the front (e.g., ocean) and the back (e.g.,bay, sound, or river). In a similar manner, at any given site, flowvelocities can vary from close to zero to very high. For these reasons,when determining flood loads for building design, velocitiesshould be estimated conservatively and it should be assumed thatfloodwaters can approach from the most critical direction andthat flow velocities can be high.Despite the uncertainties, there are methods to approximatecoastal flood velocities. One common method is based on thestillwater depth (flood depth without waves). Designers shouldconsider the topography, the distance from the source of flooding,and the proximity to other buildings and obstructions before selectingthe flood velocity for design. Those factors can direct andconfine floodwaters, with a resulting acceleration of velocities.This increase in velocities is described as the“expected upper bound.” The “expectedlower bound” velocities are experienced inareas where those factors are not expectedto influence the direction and velocity offloodwaters.2-20 MAKING CRITICAL FACILITIES SAFE FROM Flooding

Figure 2-7 shows the general relationship between velocity andstillwater depth. For design purposes, actual flood velocities are assumedto lie between the upper and lower bounds. Conservativedesigns will take into account the upper bound velocities.Figure 2-7:Velocity as a function ofstillwater flood depth2.1.2.4 Hydrostatic LoadsHydrostatic loads occur when water comes into contact witha building or building component, both above and below theground level. They act as lateral pressure or vertical pressure(buoyancy). Hydrostatic loads on inclined or irregular surfacesmay be resolved into lateral and vertical loads based on the surfacegeometry and the distribution of hydrostatic pressure.Lateral hydrostatic loads are a direct function of water depth (seeFigure 2-8). These loads can cause serious deflection or displacementof buildings or building components if there is a substantialdifference in water levels on opposite sides of the component(or inside and outside of the building). Hydrostatic loads are balancedon foundation elements of elevated buildings, such as piersMAKING CRITICAL FACILITIES SAFE FROM Flooding2-21

and columns, because the element is surrounded by water. If notoriented parallel to the flow of water, shearwalls may experiencehydrostatic loads due to a difference of water depth on eitherside of the wall. To reduce excessive pressure from standingwater, floodplain management requirements in A Zones call foropenings in walls that enclose areas below the flood elevation(see description of continuous perimeter wall foundation in Section2.3.1.2).Buoyant forces resulting from the displacement of water arealso of concern, especially for dry floodproofed buildings andaboveground and underground tanks. Buoyancy force is resistedby the dead load of the building or the weight of the tank.When determining buoyancy force, the weight of occupantsor other live loads (such as the contents of a tank) should notbe considered. If the building or tank does not weigh enough“empty,” then additional stabilizing measures need to be takento avoid flotation. This becomes a significant consideration fordesigns intended to dry floodproof a building. Buoyancy forceis slightly larger in saltwater, because saltwater weighs slightlymore than fresh water.Figure 2-8: Hydrostatic loads on buildings2-22 MAKING CRITICAL FACILITIES SAFE FROM Flooding

2.1.2.5 Hydrodynamic LoadsWater flowing around a building or a structural element that extendsbelow the flood level imposes hydrodynamic loads. Theloads, which are a function of flow velocity and structure geometry,include frontal impact on the upstream face, drag along thesides, and suction on the downstream side (see Figure 2-9). Waysto determine or estimate flood velocities are described in Section2.1.2.2 and Section 2.1.2.3.Figure 2-9: Hydrodynamic loads on a building or building elementThe most common computation methods for hydrodynamicloads are outlined in the design standard Minimum Design Loadsfor Buildings and Other Structures, produced by the AmericanSociety of Civil Engineers’ Structural Engineers Institute (ASCE/SEI, 2005). Those methods assume that the flood velocity is constant(i.e., steady state flow) and that the dynamic load imposedby floodwaters moving at less than 10 feet per second can beconverted to an equivalent hydrostatic load. This conversion is accomplishedby adding an equivalent surcharge depth to the depthof water on the upstream side. The equivalent surcharge depth isa function of the velocity. Loads imposed by floodwaters with ve-MAKING CRITICAL FACILITIES SAFE FROM Flooding2-23

locities greater than 10 feet per second cannot be converted toequivalent hydrostatic loads. Instead, they must be determined accordingto the principles of fluid mechanics or hydraulic models.Hydrodynamic loads become important when flow reachesmoderate velocities of 5 feet per second. The components of hydrodynamicloads are laterally imposed, caused by the impact ofthe mass of water against the building, and drag forces along thewetted surfaces. Drag coefficients for common building elements,such as columns and piers, can be found in a number of sources.ASCE 7 recommends values for a variety of conditions.Another component of hydrodynamic loads is wave loads. As describedin ASCE 7, “design and construction of buildings andother structures subject to wave loads shall account for the followingloads: waves breaking on any portion of the buildingor structure; uplift forces caused by shoaling waves beneath abuilding or structure, or portion thereof; wave runup striking anyportion of the building or structure; wave-induced drag and inertiaforces; and wave-induced scour at the base of a building orstructure, or its foundation.”Wave forces striking buildings and building elements can be 10to 100 or more times higher than wind forces and other forces.Forces of this magnitude can be substantial, even when actingover the relatively small surface area of the supporting structureof elevated buildings. Post-storm damage inspections show thatbreaking wave loads overwhelm virtually all wood-frame and unreinforcedmasonry walls below the wave crest elevation. Onlyengineered and massive structural elements are capable of withstandingbreaking wave loads. The magnitude of wave forces isthe rationale behind the floodplain management requirement forthe bottom of the lowest horizontal structural member to be ator above the design flood elevation in environments where wavesare predicted to be 3 feet or higher (V Zones). Because waves aslow as 1.5 feet can impose considerable loads, there is a growingawareness of the value of accounting for waves in areas that are referredto as “Coastal A Zones.”Computation of wave loads depends on the determination of waveheight. Equations for wave height are based on the assumptionthat waves are depth-limited (on the order of 75 to 80 percent of2-24 MAKING CRITICAL FACILITIES SAFE FROM Flooding

stillwater depth) and that waves propagating into shallow waterbreak when the wave height reaches a certain proportion of theunderlying stillwater depth. These assumptions are used by FEMAto determine coastal high hazard areas (V Zones) where breakingwaves are predicted to be 3 feet or higher. At any given site, waveheights may be moderated by other factors. Designers should referto ASCE 7 for detailed discussion and computation procedures.Breaking wave loads on vertical walls or supporting structuralmembers reach a maximum when the direction of wave approachis perpendicular to the wall. The duration of individual loads isbrief, with peak pressures probably occurring within 0.1 to 0.3seconds after the wave breaks. It is common to assume that thedirection of approach will be perpendicular to the shoreline, inwhich case the orientation of the wall to the shoreline will influencethe magnitude of the load placed on the wall. ASCE 7provides a method for reducing breaking wave loads on verticalwalls for waves that approach a building from a direction otherthan straight on. Structures should be designed for repetitive impactloads that occur during a storm. Some storms may last for justa few hours, as hurricanes move through the area, or for severaldays, as during some winter coastal storms (nor’easters) that affectthe Mid-Atlantic and northeastern States.2.1.2.6 Debris Impact LoadsDebris impact loads are imposed on a building or building elementsby objects carried by moving water. Objects commonlycarried by floodwaters include trees, dislodged tanks, and remnantsof manmade structures such as docks and buildings (seeFigure 2-10). Extreme impact loads result from less commonsources, such as shipping containers, boats, and barges. Themagnitude of these loads is very difficult to predict, yet some reasonableallowance should be made during the design process.Impact loads are influenced by the location of the building inthe potential debris stream. The potential for debris impacts issignificant if a building is located immediately adjacent to, ordownstream from, other buildings, among closely-spaced buildings,or downstream from large floatable objects. While theseconditions may be observable in coastal areas, it is more diffi-MAKING CRITICAL FACILITIES SAFE FROM Flooding2-25

cult to estimate the potential for debris in riverine flood hazardareas. Any riverine waterway, whether a large river or smallerurban stream, can carry large quantities of debris, especiallyuprooted trees.Figure 2-10:The South CameronMemorial Hospital,Cameron, LA, wasdamaged by debriscarried by HurricaneKatrina’s storm surge(2005).Source: LSU AGCENTERThe basic equation for estimating the magnitude of impact loadsdepends on several variables that must be selected by the designer.These variables include several coefficients, building or buildingelement stiffness, debris weight, debris velocity, and duration ofimpact. The latter three variables, described in more detail inASCE 7, are briefly described below.Debris weight: Debris weight is one of the more difficult variablesto estimate. Unless otherwise indicated by field conditions, ASCE7 recommends using an average object weight of 1,000 pounds.This weight corresponds to a 30-foot long log only 1 foot in diameter,small in comparison to large trees that may be uprootedduring a flood. In coastal areas, expected debris weights dependon the nature of the debris. In the Pacific Northwest, large treesand logs are common, with weights in excess of 4,000 pounds. Inareas where piers and pilings are likely to become debris, 1,000pounds is reasonable. In areas where most debris is likely to resultfrom building damage (failed decks, steps, failed walls, propanetanks), the average debris weight may be less than 500 pounds.2-26 MAKING CRITICAL FACILITIES SAFE FROM Flooding

Debris velocity: The velocity of the debris depends on the natureof the debris and the velocity of floodwaters. For the impact loadcomputation, the velocity of the water-borne object is assumed tobe the same as the flood velocity. Although this assumption is reasonablefor smaller objects, it is conservative for large objects.Debris impact duration: Duration of impact is the elapsed timeduring which the impact load acts on the building or building element.The duration of impact is influenced primarily by thenatural frequency 2 of the building or element, which is a functionof the building’s stiffness. Stiffness is determined by theproperties of the material, the number of supporting members(columns or piles), the height of the building above the ground,and the height at which the element is struck. Despite all the variablesthat may influence duration of impact, early assumptionssuggested a 1-second duration. A review of results from severallaboratory tests that measured impacts yielded much briefer periods,and ASCE 7 currently recommends a duration of 0.03second.2.1.2.7 Erosion and Localized ScourErosion generally refers to a lowering of the ground surface as aresult of a flood event. Erosion may occur in riverine and coastalflood hazard areas. In coastal areas, erosion may affect the generalground surface and may cause a short-term or long-term recession ofthe shoreline. Erosion should be considered during load calculations,because it increases the local flood depth, which in turn influencesload calculations. In areas subject to gradual erosion of the ground surface,additional foundation embedment depth can mitigate the effects.However, where waterways are prone to changing channels andwhere shoreline erosion is significant, engineered solutions areunlikely to be effective. Avoidance of sites in areas subject to activeerosion is the safest and most cost-effective course of action.Localized scour results from turbulence at the ground levelaround foundation elements. Scour occurs in both riverine andcoastal flood hazard areas, especially in areas with erodible soils.2. The frequency at which an object will vibrate freely when set in motion.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-27

Determining potential scour is critical in the design of foundationsto ensure that failure during and after flooding does not occur asa result of the loss in either bearing capacity or anchoring resistancearound the posts, piles, piers, columns, footings, or walls (seeFigure 2-11). Scour determinations require knowledge of the flooddepth, flow conditions, soil characteristics, and foundation type.At some locations, soil at or below the ground surface can be resistantto localized scour, and calculated scour depths based onunconsolidated surface soils below will be excessive. In instanceswhere the designer believes the underlying soil at a site will bescour-resistant, the assistance of a geotechnical engineer or geologistshould be sought.Figure 2-11:Local scour underminedthis shallow foundation(also note that the buildingwas not anchored to thefoundation).2.1.3 FLOODPLAIN MANAGEMENTREQUIREMENTS AND BUILDING CODESThe NFIP is the basis for the minimum requirements included inmodel building codes and standards for design and constructionmethods to resist flood damage. The original authorizing legislationfor the NFIP is the National Flood Insurance Act of 1968 (42U.S.C. 4001 et seq.). In that act, Congress expressly found that “aprogram of flood insurance can promote the public interest byencouraging sound land use by minimizing exposure of propertyto flood losses…”2-28 MAKING CRITICAL FACILITIES SAFE FROM Flooding

The most convincing evidence of the effectiveness of the NFIPminimum requirements is found in flood insurance claim paymentstatistics. Buildings that pre-date the NFIP requirementsare, by and large, not constructed to resist flood damage. Buildingsthat post-date the NFIP (i.e., those that were constructedafter a community joined the program and began applying theminimum requirements) are designed to resist flood damage.The NFIP reports that aggregate loss data indicate that buildingsthat meet the minimum requirements experience 70 percent lessdamage than buildings that pre-date the NFIP. There is ampleevidence that buildings designed to exceed the minimum requirementsare even less likely to sustain damage.2.1.3.1 Overview of the NFIPThe NFIP is based on the premise that the Federal governmentwill make flood insurance available in communities that agree torecognize and incorporate flood hazards in land use and developmentdecisions. In some States and communities this is achievedby guiding development to areas with a lower risk. When decisionsresult in development within flood hazard areas, applicationof the criteria set forth in Federal regulation 44 CFR §60.3 are intendedto minimize exposure and flood-related damage. Stateand local governments are responsible for applying the provisionsof the NFIP through the regulatory permitting processes. At theFederal level, the NFIP is managed by FEMA and has three mainelements:m Hazard identification and mapping, under which engineeringstudies are conducted and flood maps are prepared inpartnership with States and communities. These mapsdelineate areas that are predicted to be subject to floodingunder certain conditions.m Floodplain management criteria for development, whichestablish the minimum requirements to be applied todevelopment within mapped flood hazard areas. The intent isto recognize hazards in the entire land development process.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-29

m Flood insurance, which provides some financial protection forproperty owners to cover flood-related damage to buildingsand contents.“Substantial damage” is damage of anyorigin sustained by a structure wherebythe cost of restoring the structure to itscondition before the damage wouldequal or exceed 50 percent of the marketvalue of the structure before the damageoccurred.“Substantial improvement” is any repair,reconstruction, rehabilitation, addition,or improvement of a building, the costof which exceeds 50 percent of themarket value of the building before theimprovement or repair is started (certainhistoric structures may be excluded).Federal flood insurance is intended to shiftsome of the costs of flood disasters awayfrom the taxpayer by providing propertyowners an alternative to disaster assistanceand disaster loans. Disaster assistance provideslimited funding for repair and cleanup,and is available only after the Presidentsigns a major disaster declaration for thearea. NFIP flood insurance claims are paidany time damage from a qualifying floodevent 3 occurs, regardless of whether a majordisaster is declared. Community officialsshould be aware that public buildings maybe subject to a mandated reduction in disasterassistance payments if the building isin a mapped flood hazard area and is notcovered by flood insurance.Another important objective of the NFIP is to break the cycle offlood damage. Many buildings have been flooded, repaired or rebuilt,and flooded again. Before the NFIP, in some parts of thecountry this cycle occurred every couple of years, with reconstructiontaking place in the same flood-prone areas, using thesame construction techniques that did not adequately resist flooddamage. NFIP provisions guide development to lower risk areasby requiring compliance with performance measures to minimizeexposure of new buildings and buildings that undergo major renovationor expansion (called “substantial improvement” or repairof “substantial damage”). This achieves the long-term objective ofbuilding disaster-resistant communities.3. For the purpose of adjusting claims for flood damage, the NFIP defines a flood as “a general and temporary condition of partial or completeinundation of two or more acres of normally dry land area or of two or more properties (at least one of which is the policyholder’s property)from: overflow of inland or tidal waters; unusual and rapid accumulation or runoff of surface waters from any source; mudflow; or collapse orsubsidence of land along the shore of a lake or similar body of water as a result of erosion or undermining caused by waves or currents of waterexceeding anticipated cyclical levels that result in a flood as defined above.”2-30 MAKING CRITICAL FACILITIES SAFE FROM Flooding

2.1.3.2 Summary of the NFIP MinimumRequirementsThe performance requirements of the NFIP are set forth in Federalregulation 44 CFR Part 60. The requirements apply to alldevelopment, which the NFIP broadly defines to include buildingsand structures, site work, roads and bridges, and other activities.Buildings must be designed and constructed to resist flooddamage, which is primarily achieved through elevation (or floodproofing).Additional specific requirements apply to existingdevelopment, especially existing buildings. Existing buildings thatare proposed for substantial improvement, including restorationfollowing substantial damage, are subject to the regulations.Although the NFIP regulations primarily focus on how to buildstructures, one of the long-term objectives of the program is toguide development to less hazardous locations. Preparing floodhazard maps and making the information available to the publicis fundamental in satisfying that objective. With that information,people can make informed decisions about where to build, how touse site design to minimize exposure to flooding, and how to designbuildings that will resist flood damage.The NFIP’s broad performance requirements for site work inflood hazard areas are as follows:m Building sites shall be reasonably safe from flooding.m Adequate site drainage shall be provided to reduce exposureto flooding.m New and replacement sanitary sewage systems shall bedesigned to minimize or eliminate infiltration of floodwatersinto the systems and discharges from the systems intofloodwaters.m Development in floodways shall be prohibited, unlessengineering analyses show that there will be no increases inflood levels.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-31

The NFIP’s broad performance requirements for new buildingsproposed for flood hazard areas (and substantial improvement ofexisting flood-prone buildings) are as follows:m Buildings shall be designed and adequately anchored toprevent flotation, collapse, or lateral movement resulting fromhydrodynamic and hydrostatic loads, including the effects ofbuoyancy.m Building materials used below the design flood elevation shallbe resistant to flood damage.m Buildings shall be constructed to minimize flood damage(primarily by elevating to or above the base flood level, or byspecially designed and certified floodproofing measures).m Buildings shall be constructed with electrical, heating,ventilation, plumbing, and air conditioning equipment andother service facilities designed to prevent water from enteringor accumulating within the components.States often use governors’ executiveorders to influence State-constructed andState-funded critical facilities, requiringlocation outside of the 500-year floodplainwhere feasible, or protection to the500-year flood level if avoiding thefloodplain is not practical. In 2004, areview of State and local floodplainmanagement programs determined thatAlabama, Illinois, Michigan, New York,North Carolina, Ohio, and Virginia haverequirements for critical facilities (ASFPM,2004).Owners, planners and designers shoulddetermine if there are any applicableState-specific requirements for floodplain development.Some States require that localjurisdictions apply standards that exceedthe minimum requirements of the NFIP. Inparticular, some States require that critical facilitiesbe located outside of the floodplain(including the 500-year floodplain) or theyare to be designed and constructed to resistconditions associated with the 500-year flood.Some States have regulations that imposeother higher standards, while some Stateshave direct permitting authority over certaintypes of construction or certain types ofapplicants.As participants in the NFIP, States are required to ensure that developmentthat is not subject to local regulations, such as Stateconstruction, satisfies the same performance requirements. Ifcritical facilities are exempt from local permits, this may be ac-2-32 MAKING CRITICAL FACILITIES SAFE FROM Flooding

complished through a State permit, a governor’s executive order,or other mechanisms that apply to entities not subject to localauthorities.2.1.3.3 Executive Order 11988 and CriticalFacilitiesWhen Federal funding is provided for the planning, design,and construction of new critical facilities, or for the repair of existingcritical facilities located within the 500-year floodplain, thefunding agency is required to address additional considerations.Executive Order 11988, Floodplain Management, requires Federalagencies to apply a decisionmaking process to avoid, to the extentpossible, the long- and short-term adverse impacts associated withthe occupancy and modification of floodplains, and to avoid thedirect or indirect support of floodplain development wheneverthere is a practicable alternative. If there is no practicable alternative,the Federal agency must minimize any adverse impacts to life,property, and the natural and beneficial functions of floodplains.The executive order establishes the base flood elevation as theminimum standard for all Federal agencies. Implementation guidancespecifically addresses “critical actions,” which are describedas those actions for which even a slight chance of flooding wouldbe too great. The construction or repair of critical facilities, suchas fire stations, hospitals and clinics, EOCs, the storage of hazardouswastes, and the storage of critical records, are examples ofcritical actions.After determining that a site is in a mappedflood hazard area, and after giving publicFEMA’s eight-step decisionmaking processnotice, the Federal funding agency is requiredto identify and evaluate practicable must be applied before Federal disasterfor complying with Executive Order 11988alternatives to locating a critical facility in a assistance is used to repair, rehabilitate,500-year floodplain. If the Federal agency or reconstruct damaged existing criticalhas determined that the only practicable alternativeis to proceed, then the impacts offacilities in the 500-year floodplain.the proposed action must be identified. Ifthe identified impacts are harmful to people, property, and thenatural and beneficial functions of the floodplain, the FederalMAKING CRITICAL FACILITIES SAFE FROM Flooding2-33

agency is required to minimize the adverse effects on the floodplainand the funded activity.Having identified the impacts of the proposed action and themethods to minimize these impacts, the Federal agency is requiredto re-evaluate the proposed action. The re-evaluation mustconsider whether the action is still feasible, whether the action canbe modified to relocate the facility or eliminate or reduce identifiedimpacts, or if a “no action” alternative should be chosen. Ifthe finding results in a determination that there is no practicablealternative to locating a critical facility in the floodplain, or otherwiseaffecting the floodplain, then a statement of findings and apublic explanation must be provided.2.1.3.4 Scope of Model Building Codes andStandardsThe International Building Code (IBC, 2003) and the Building Constructionand Safety Code (NFPA 5000, 2003) were the first modelcodes to include comprehensive provisions that address flood hazards.Both codes are consistent with the minimum provisions ofthe NFIP that pertain to the design and construction of buildings.The NFIP requirements that pertain to site development,floodways, coastal setback lines, erosion-prone areas, and other environmentalconstraints are found in other local ordinances. Thecodes require designers to identify and design for anticipated environmentalloads and load combinations, including wind, seismic,snow, and flood loads, as well as the soil conditions.The IBC and NFPA 5000 incorporate by reference a number of standardsthat are developed through a rigorous consensus process. Thebest known is Minimum Design Loads for Buildings and Other Structures(ASCE 7-05). The model building codes require that applicableloads be accounted for in the design. The 1998 edition of ASCE 7was the first version of the standard to include flood loads explicitly,including hydrostatic loads, hydrodynamic loads (velocity andwaves), and debris impact loads.The IBC and NFPA 5000 also incorporate by reference a standardthat was first published by ASCE in 1998 and revised in2005, Flood Resistant Design and Construction (ASCE/SEI 24-05).2-34 MAKING CRITICAL FACILITIES SAFE FROM Flooding

Developed through a consensus process,ASCE 24 addresses specific topics pertinentto designing buildings in flood hazard areas,including floodways, coastal high hazardareas, and other high-risk flood hazard areassuch as alluvial fans, flash flood areas, mudslideareas, erosion-prone areas, and highfloodwater velocity areas.Section 1.2 describes the four categories usedby ASCE 7 to classify structures based on occupancy;different requirements apply based ona structure’s category. The same categories are used in ASCE 24and different flood-resistant requirements apply to the differentcategories. Table 2-1 summarizes the elevation requirements ofASCE 24 that exceed the NFIP minimum requirements for thecritical facilities addressed by this manual (Category III or CategoryIV structures).ASCE 7-05 outlines methods to determinedesign loads and load combinations inflood hazard areas, including hydrostaticloads, hydrodynamic loads, wave loads,and debris impact loads.ASCE 24-05 addresses designrequirements for structures in coastal highhazardareas (V Zones).MAKING CRITICAL FACILITIES SAFE FROM Flooding2-35

Table 2-1: ASCE/SEI 24-05 provisions related to the elevation of critical facilitiesCategory IIICategory IVElevation of Lowest Floor or Bottomof Lowest Horizontal StructuralA Zone: elevation of lowest floorV Zone and Coastal A Zone: where thelowest horizontal structural member is parallelto direction of wave approachV Zone and Coastal A Zone: where thelowest horizontal structural member isperpendicular to direction of wave approachBFE +1 ft or DFE,whichever is higherBFE +1 ft or DFE,whichever is higherBFE +2 ft or DFE,whichever is higherBFE +2 ft or DFE,whichever is higherBFE +1 ft or DFE,whichever is higherBFE +2 ft or DFE,whichever is higherElevation Below which Flood-Damage-Resistant Materials ShallA ZoneV Zone and Coastal A Zone: where thelowest horizontal structural member is parallelto direction of wave approachV Zone and Coastal A Zone: where thelowest horizontal structural member isperpendicular to direction of wave approachBFE +1 ft or DFE,whichever is higherBFE +2 ft or DFE,whichever is higherBFE +3 ft or DFE,whichever is higherBFE +2 ft or DFE,whichever is higherBFE +2 ft or DFE,whichever is higherBFE +3 ft or DFE,whichever is higherMinimum Elevation of Utilities andEquipmentA ZoneV Zone and Coastal A Zone: where thelowest horizontal structural member is parallelto direction of wave approachV Zone and Coastal A Zone: where thelowest horizontal structural member isperpendicular to direction of wave approachBFE +1 ft or DFE,whichever is higherBFE +2 ft or DFE,whichever is higherBFE +3 ft or DFE,whichever is higherBFE +2 ft or DFE,whichever is higherBFE +2 ft or DFE,whichever is higherBFE +3 ft or DFE,whichever is higherDryFloodproofingA Zone: elevation to which dry floodproofingextendsV Zone and Coastal A Zone: dryfloodproofing not allowedBFE +1 ft or DFE,whichever is higherNot applicableBFE +2 ft or DFE,whichever is higherNot applicable2-36 MAKING CRITICAL FACILITIES SAFE FROM Flooding

2.2 CRITICAL FACILITIES EXPOSED TOFLOODING2.2.1 EVALUATING RISK AND AVOIDINGFLOOD HAZARDSFlood hazards are very site-specific.When a flood hazard map is prepared, Even in communities with expansivelines drawn on the map appear to preciselydefine the hazard area. Land that is on locating new critical facilities in floodwaysfloodplains, it should be possible to avoidone side of the line is “in” the mapped flood and coastal areas subject to significanthazard area, while the other side of the line waves (V Zones).is “out.” Although the delineation may be anapproximation, having hazard areas shownon a map facilitates avoiding such areas to the maximum extentpractical. Where it is unavoidable, facility owners should carefullyevaluate all of the benefits and all of the costs in order to determinelong-term acceptable risks, and to develop appropriate plansfor design and construction of new facilities.Section 2.2.2 describes the damage sustained by existing buildingsexposed to flood hazards, including site damage, structuraland nonstructural building damage, destruction or impairment ofservice equipment, and loss of contents. These types of damage,along with loss of function and community service, are avoided ifcritical facilities are located away from flood hazard areas. Damageis reduced when critical facilities that must be located in floodhazard areas are built to exceed the minimum requirements.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-37

2.2.1.1 Benefits/Costs: Determining AcceptableRiskMany decisions that are made with respect toExtreme hurricane storm surge flooding critical facilities are, in part, based on a determinationof acceptable risk. Risk includesmay be a very low-probability event, butthe flood water depths and waves may the potential losses associated with a hazard.be much more severe than the conditions Ideally, risk is defined in terms of expectedof the base flood shown on the FIRMs. probability and frequency of the hazard occurring,the people and property exposed,The potential impacts on a critical facilitymust be carefully considered in order to and the potential consequences. Choosingmake an informed decision regardinga site that is affected by flooding is a decisionto accept some degree of risk. Althoughacceptable risk and potential damage. Ifpossible, it is always best to avoid locating the flood-prone land may have a lower initialcritical facilities in areas subject to extreme cost, the incremental costs of construction,storm surge flooding.plus the likely increased costs of maintenance,repair, and replacement, may besignificant. Another cost of locating a criticalfacility in a flood-prone area is related to access problems if roadsand driveways are impassable. Although the building may be elevatedand protected, if access is restricted periodically, then theuse of the facility is affected.The building owner and the design team can influence the degreeof risk (e.g., the frequency with which flooding may affect thesite). They control it through the selection of the site design andthe building design measures. Fundamentally, this process is a balancingof the benefits of an acceptable level of disaster resistancewith the costs of achieving that degree of protection. With respectto mitigation of future hazard events:m Benefits are characterized and measured as future damagesavoided if the mitigation measures (including avoiding floodhazard areas) are implemented.m Costs are the costs associated with implementing measures toeliminate or reduce exposure to hazards.Section 2.2.2 describes damage and losses that are incurred bybuildings exposed to flooding. Direct damage includes damage tophysical property, including the site, the building, building materials,utilities, and building contents. Indirect damage that is not2-38 MAKING CRITICAL FACILITIES SAFE FROM Flooding

listed includes health hazards, loss of functionality,emergency response, evacuation,and expenses associated with occupying anotherbuilding during repairs.Benefits other than avoided physical damageare difficult to measure. They are associatedwith future damage that does not occur becauseof the mitigation activity, cleanup thatis not required because of the mitigation activity,and service that is not interruptedbecause flooding does not affect normaloperation of the facility. In addition, benefitsaccrue over long periods of time, thusmaking it more difficult to make a direct comparison of the benefitswith the up-front costs of mitigation. Mitigation costs can bemore readily expressed in terms of the higher costs of a floodfreesite, or the initial capital costs of work designed to resist flooddamage. Thus, without a full accounting of both benefits andcosts, decisionmakers may not be able to make fully informed decisions.Some questions that should be answered include:m If the site is flood-prone and the building is out of the floodhazard area or is elevated on fill, what are the average annualcleanup costs associated with removal of sand, mud, and debrisdeposited by floods of varying frequencies?m If the facility building is elevated by means other than fill, willperiodic inundation of the exposed foundation elements causehigher average annual maintenance costs?m If the facility is protected with floodproofing measures, whatare the costs of annual inspections, periodic maintenanceand replacement of materials, and staff training and periodicdrills?m If the critical facility meets only the minimum elevationrequirements, what are the average annual damage andcleanup costs over the anticipated useful life of the building,including the occurrence of floods that exceed the designflood elevation?Sometimes developers are required toset aside land to meet adequate facilitiesrequirements, or land may be donated tosupport community or non-profit facilities,such as fire stations. If the donated landis affected by flood hazards, it may bedifficult to avoid floodplain impacts entirely.Careful consideration should be madewhether the benefits of accepting the landoutweigh the costs and risks associatedwith mitigating the flood risk.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-39

m How do long-term costs associated with periodic inundationcompare to up-front costs of selecting a different site orbuilding to a higher level of protection?m If the facility is located in a hurricane-prone community, howshould the facility design account for low probability, but highimpact, storm surge flooding?m If access to the facility is periodically restricted due to flooding,especially long-duration flooding, what are the cost effects?How often should an alternate location be provided tocontinue normal operations?2.2.1.2 Identifying Flood Hazards at CriticalFacilities SitesAs part of site selection and to guide locating a new critical facilityand other improvements on a site, facility owners, planners, anddesigners should investigate site-specific flood hazard characteristics.Similarly, when examining existing critical facilities andwhen planning improvements or rehabilitation work, an importantstep is to determine the site characteristics and flood hazards.The best available information should be examined, includingflood hazard maps, records of historical flooding, storm surgemaps, and advice from local experts and others who can evaluateflood risks. Table 2-3 in Section 2.5 outlines questions that shouldbe answered prior to initiating site layout and design work.2.2.1.3 Critical Facilities as Emergency SheltersEmergency managers regularly identify facilities (especiallyschools) to serve as short-term and long-term shelters. Schoolsare attractive sites for shelters because they have kitchen facilitiesdesigned to serve many people, restroom facilities likely to beadequate for many people, and plenty of space for cots in gymnasiums,cafeterias, and wide corridors.New schools that will function as emergency shelters warrant ahigher degree of protection than other schools and should be appropriatelydesigned as critical facilities (see Section 1.3 for an2-40 MAKING CRITICAL FACILITIES SAFE FROM Flooding

overview on performance-based design). If located in, or adjacentto, flood hazard areas, it is appropriate to provide protectionfor the building and utility systems to at least the 0.2-percent-annual-chance(500-year) flood level or, at a minimum, 2 to 3 feetabove the DFE. Additional guidance on hazard-resistant shelters isfound in FEMA 361, Design and Construction Guidance for CommunityShelters.Additional measures that may be appropriate for considerationwhen flood-prone critical facilities are used as shelters include thefollowing:m Wastewater service must be functional during conditions of theflooding.m Emergency power service must be provided.m Dry ground access is important, in the event flooding exceedsdesign levels.2.2.2 VULNERABILITY: WHAT FLOODINGCAN DO TO EXISTING CRITICALFACILITIESExisting flood-prone facilities are susceptible to damage, the natureand severity of which is a function of site-specific floodcharacteristics. As described below, damage may include: sitedamage, structural and nonstructural building damage, destructionor impairment of utility service equipment and loss ofcontents.Regardless of the nature and severity of damage, flooded facilitiestypically are not functional while cleanup and repairs areundertaken. The length of closure, and thus the impact on theability of the facility to become operational, depends on the severityof the damage and lingering health hazards. Sometimesrepairs are put on hold pending a decision on whether a facilityshould be rebuilt at the flood-prone site. When damageis substantial, rehabilitation or reconstruction is allowed only ifcompliance with flood-resistant design requirements is achieved(see Section 2.1.3.2).MAKING CRITICAL FACILITIES SAFE FROM Flooding2-41

2.2.2.1 Site DamageThe degree of site damage associated with flooding is a functionof several variables related to the characteristics of the flood, aswell as the site itself.Erosion and scour: All parts of a site subject to flooding by fastmoving water could experience erosion, and local scour couldoccur around any permanent obstructions to flow. Gradedareas, filled areas, and cut or fill slopes are especially susceptible.Stream and channel bank erosion, and erosion ofcoastal shorelines, are natural phenomena that may, over time,threaten site improvements and buildings.Debris and sediment removal: Even when buildings are not subjectto water damage, floods can produce large quantities of debrisand sediment that can damage a site and be expensive toremove.Landscaping: Grass, trees, and plants suffer after floods, especiallylong-duration flooding that prevents oxygen uptake, andcoastal flooding that stresses plants that are not salt-tolerant.Fast-moving floodwaters and waves also can uproot plants andtrees.Fences: Some types of fences that are relatively solid can significantlyrestrict the free flow of floodwaters and trap floatingdebris. Fences can be damaged by flowing water, and can beknocked down under pressure of flowing water or if the buildupof debris results in significant loads (see Figure 2-12).Accessory structures: Accessory structures can sustain both structuraland nonstructural damage. In some locations, suchstructures can be designed and built using techniques thatminimize damage potential, without requiring elevation abovethe DFE.Access roads: Access roads that extend across flood-prone areasmay be damaged by erosion, washout of drainage culverts,failure of fill and bedding materials, and loss of surface (seeFigure 2-13). Road damage could prevent uninterrupted accessto a facility and thus impair its functionality.2-42 MAKING CRITICAL FACILITIES SAFE FROM Flooding

Figure 2-12:Katrina’s storm surge flooding knocked down thisfence adjacent to a fire station (2005).Figure 2-13:Flooding caused the failure of this road bed.Source: U.S. Army Corps of EngineersParking lots and parking garages: Paved parking lots may be damagedby failure of bedding materials and loss of driving surface.Vehicles left in parking lots and parking garages could also bedamaged. Most large parking garages are engineered structuresthat can be designed to allow for the flow of water.Stormwater management facilities and site drainage: Site improvementssuch as swales and stormwater basins may be eroded,filled with sediments, or clogged by debris.2.2.2.2 Structural DamageStructural damage includes all damage to the load-bearing portionsof a building. Structural damage can be caused by eachof the characteristics of flooding described in Section 2.1.1.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-43

Damage to other components of buildings is described below,including saturation of materials (Section 2.2.2.3), utility serviceequipment (Section 2.2.2.4), and contents (Section 2.2.2.5).Depth: The hydrostatic load or pressure against a wall or foundationis directly related to the depth of water (refer to Figure2-9). Standard stud and siding, or unreinforced brick veneerwalls, may collapse under hydrostatic loads associated with relativelyshallow water. Reinforced masonry walls perform betterthan unreinforced masonry walls (see Figure 2-14), althoughan engineering analysis is required to determine performance.Walls and floors of below-grade areas (basements) are particularlysusceptible to damage by hydrostatic pressure. When soilsare saturated, pressures against below-grade walls are a functionof the total depth of water, including the depth below-grade andthe weight of the saturated soils.Figure 2-14:Interior unreinforcedmasonry walls of the PortSulphur High School inLouisiana were damagedby hydrostatic loadsassociated with HurricaneKatrina’s storm surge(2005).2-44 MAKING CRITICAL FACILITIES SAFE FROM Flooding

Buoyancy and uplift: If below-grade areas are essentially watertight,buoyancy or uplift forces can float a building out of the ground orrupture concrete floors (see Figure 2-15). Buildings that are notadequately anchored can be floated or pushed off foundations. Althoughrare for large and heavy critical facility buildings, this is aconcern for outbuildings and portable (temporary) units.Figure 2-15:Concrete floor rupturedby hydrostatic pressure(buoyancy). HurricaneKatrina (2005)Duration: Long duration saturation can cause dimensional changesand contribute to deterioration of wood members. By itself, saturationis unlikely to result in significant structural damage to masonryconstruction. Saturation of soils, a consequence of long durationflooding, increases pressure on below-grade foundation walls.Velocity, wave action, and debris impacts: Each of these componentsof dynamic loads can result in structural damage if buildings arenot designed to resist overturning, repetitive pounding by waves,or short-duration impact loads generated by floating debris.Erosion and scour: Structural damage is associated with foundationfailure when erosion or scour results in partial or completeremoval of supporting soil (see Figure 2-16). Erosion of slopes, especiallyunprotected slopes, can lead to slope failures and loss offoundation supporting soil.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-45

Figure 2-16:Scour around thefoundation of this buildingcontributed to significantdamage.2.2.2.3 Nonstructural DamageMany flood-prone buildings are exposed to floodwaters that arenot fast moving, or that may be relatively shallow and not resultin structural damage. Simple inundation and saturation of thebuilding and finish materials can result in significant and costlynonstructural damage, including long-term health complicationsassociated with mold. Floodwaters often are contaminatedwith chemicals, petroleum products, or sewage. Under such circumstances,recovery generally involves removal of nonstructuralmaterials and finishes because cleanup and decontamination is expensiveand time-consuming. Damage to contents is discussed inSection 2.2.2.5.Nonstructural damage can vary as a function of the duration ofwater exposure. Some materials are not recoverable even aftervery brief inundation, while others remain serviceable if in contactwith water for only a few hours. Use of water-resistant materialswill help to minimize nonstructural damage caused by saturationand reduce the costs of cleanup and restoration to service (seeFlood-Resistant Materials Requirements, FIA-TB-2).Wall finishes: Painted concrete and concrete masonry walls usuallyresist water damage, provided the type of paint can be readilycleaned, such as high strength epoxy paints. Tiled walls may be2-46 MAKING CRITICAL FACILITIES SAFE FROM Flooding

acceptable, depending on the type of adhesive and foundation(gypsum board substrate and wood-framed walls with tile typicallydo not remain stable).Flooring: Many critical facilities have durable floors that resistwater damage. Ground floors often are slab-on-grade and finishedwith tile or sheet goods. Flooring adhesives in use sincethe early 1990s likely are latex-based and tend to break downwhen saturated. Most carpeting, even the indoor-outdoor kind,is difficult to clean. Wood floors are particularly susceptible tosaturation damage, although short duration inundation maynot cause permanent de-formation of some wood floors. However,because of low tolerance for surface variations, gymnasiumfloors in schools are particu-larly sensitive and tend to warp afterflooding of any duration (see Figure 2-17).Figure 2-17:This parquet wood gymnasium floor wasdamaged by dimensional changes due tosaturation. Hurricane Katrina (2005)Wall and wood components: When soaked for long periods of time,some building components change composition or shape. Mosttypes of wood will swell when wetted and, if dried too quickly, willcrack, split or warp. Plywood can delaminate and wood door andMAKING CRITICAL FACILITIES SAFE FROM Flooding2-47

window frames may swell and become unstable. Gypsum wallboard,wood composition panels, other wall materials, and wood cabinetrynot intended for wet locations can fall apart (see Figure 2-18).The longer these materials are wet, the more moisture, sediment,and pollutants they absorb. Some wall materials, such as the paperfacing on gypsum wallboard, “wick” standing water, resulting indamage above the actual high-water line (see Figure 2-19).Figure 2-18:Damaged walls andcabinetsFigure 2-19:Water damage and moldgrowth extend above thewater lineSource: Oak Ridge NationalLaboratory2-48 MAKING CRITICAL FACILITIES SAFE FROM Flooding

Metal components: Metal structural components are unlikely to bepermanently damaged by short-term inundation. However, hollowmetal partitions are particularly susceptible when they come intocontact with water because they cannot be thoroughly dried andcleaned. Depending on the degree of corrosion protection on themetal, repetitive flooding by saline coastal waters may contributeto long-term corrosion.Metal connectors and fasteners: Depending on the composition of themetal, repetitive flooding, especially by saline coastal waters, maycontribute to long-term corrosion. Connectors and fasteners areintegral to the structural stability of buildings; therefore, failurecaused by accelerated corrosion would jeopardize the building.2.2.2.4 Utility System DamageUtility system service equipment that is exposed to flooding isvulnerable to damage. Damage may result in a total loss, or mayrequire substantial cleaning and restoration efforts. The degreeof damage varies somewhat as a function of the characteristics offlooding. Certain types of equipment and installation measureswill help minimize damage and reduce the costs of cleanup andrestoration to service.Displacement of equipment and appliances: Installation below theflood level exposes equipment and appliances to various floodforces, including drag resulting from flowing water and buoyancy.Gas-fired appliances are particularly dangerous: flotation can separateappliances from gas sources, resulting in fires and explosivesituations. Displaced equipment may dislodge lines from fuel oiltanks, contributing to the threat of fires and causing water pollutionand environmental damage.Elevators: If located in areas subject to flooding, elevatorcomponent equipment and controls will be damaged, andcommunication between floors will be impaired.Corrosion: Corrosion related to inundation of equipment and appliancesmay not be apparent immediately, but can increasemaintenance demand and shorten the useful life of some equipmentand appliances.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-49

Electrical systems and components: Electrical systems and components,and electrical controls of heating, ventilation, and airconditioning systems, are subject to damage simply by getting wet,even for short durations. Unless specifically designed for wet locations,switches and other electrical components can short out dueto deposits of sediment, or otherwise not function even when allowedto dry before operation. Wiring and components that havebeen submerged may be functional, although generally it is morecost-effective to discard flooded outlets, switches, and other lessexpensive components than to attempt thorough cleaning.Communications infrastructure: Critical communications infrastructure,such as control panels and wiring for warning systems, 911systems, and regular telephone and wireless networks, are mostsusceptible to failure during emergencies if located in below-gradebasements.Specialized piping: Unprotected piping for medical gas supplysystems may be damaged and threaten care that depends on uninterruptedsupply of oxygen and other gasses for the treatment ofpatients.Ductwork damage: Ductwork is subject to two flood-related problems.Flood forces can displace ductwork, and saturated insulationcan overload support straps, causing failure.Mold and dust: Furnaces, air handlers, and ductwork that have beensubmerged must be thoroughly cleaned and sanitized. Otherwise,damp conditions contribute to the growth of mold and accumulatedsediment can be circulated throughout the critical facility,causing respiratory problems. Fiberglass batt or cellulose insulationthat has been submerged cannot be sanitized and must bereplaced. In sensitive environments, ductwork should be replacedrather than cleaned.Gas-fired systems: Water-borne sediment can impair safe functioningof jets and controls in gas-fired furnaces and water heaters,necessitating professional cleaning and inspection prior to restorationof service. Control equipment (valves, electrical switches,relays, temperature sensors, circuit breakers, and fuses) that havebeen submerged may pose an explosion and fire hazard andshould be replaced.2-50 MAKING CRITICAL FACILITIES SAFE FROM Flooding

Emergency power generators: Generators that are installed at-gradeare susceptible to inundation and will be out of service after aflood (see Figure 2-20).Tanks (underground): Underground storage tanks are subjected tosignificant buoyant forces and can be displaced, especially whenlong-duration flooding occurs. Computations of stability shouldbe based on the assumption that the tank is empty in order tomaximize safety. Tank inlets, fill openings, and vents should beabove the DFE, or designed to prevent the inflow of floodwatersor outflow of tank contents during flood conditions.Tanks (aboveground): Aboveground storage tanks are subject tobuoyant forces and displacement caused by moving water. Standardstrapping of propane tanks may be inadequate for theanticipated loads. Tank inlets, fill openings, and vents should beabove the DFE, or designed to prevent the inflow of floodwatersor outflow of tank contents during flood conditions.Public Utility Service: Damage to public utility service (potablewater supply and wastewater collection) can affect operations andmay cause damage to critical facilities:Figure 2-20:Although it was anchoredand not displaced byfloodwaters, this generatorwas out of service afterbeing submerged.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-51

m Potable water supply systems may become contaminatedif public water distribution lines or treatment facilities aredamaged, or if wellheads are submerged.m During heavy rains, sewers back up from infiltration andinflow of stormwater into the sewer lines and manholes,cross connections between storm and sanitary sewers, andflooded wastewater treatment plants. Sewer backup into acritical facility poses a major health hazard. Even when thewater has receded, exposed building components, finishmaterials, and contents are contaminated, and usually mustbe removed because adequate cleaning is difficult, if notimpossible.2.2.2.5 Contents DamageCritical facilities may contain high-value contents that can be damagedand become unrecoverable when subjected to flooding. Forthe purpose of this discussion, the term “contents” includes itemssuch as furniture, appliances, computers, laboratory equipmentand materials, records, and specialized machinery. The followingtypes of contents are often considered a total loss.Furniture: In long-duration flooding, porous woods become saturatedand swollen, and joints may separate. Furniture withcoverings or pads generally cannot be restored. Metal furniture isdifficult to thoroughly dry and clean, is subject to corrosion, andtypically is discarded. Some wood furniture may be recoverableafter brief inundation.Computers: Flood-damaged computers and peripheral equipmentcannot be restored after inundation, although special recoveryprocedures may be able to recover information on hard drives.Communications equipment: Even though some communicationsequipment may be able to be restored with appropriatecleaning, the loss of functionality would seriously impair theability of the facility to provide critical services immediately aftera flood. Equipment with printed circuit boards generally cannotbe restored.2-52 MAKING CRITICAL FACILITIES SAFE FROM Flooding

Office records and police files: When facilities are located in floodpronespace, valuable records may be lost. Although expensive,some recovery of computerized and paper records may be possiblewith special procedures (see Figure 2-21).Health care equipment and laboratory materials: Most medical andhealth care equipment cannot be cleaned and restored to safefunctioning, and would need to be replaced. Depending on thenature of laboratory materials and chemicals, complete disposalor special cleanup procedures may be required.Kitchen goods and equipment: Floodwaters can dislodge appliancesthat can float and damage other equipment (see Figure 2-22).Stainless steel equipment generally has cleanable surfaces that canbe disinfected and restored to service. Because of contamination,all food stuffs must be discarded.Vehicles associated with critical facilities: If left in flood-prone areas,fire engines, police cars, ambulances, and other vehicles requirereplacement or cleaning to be serviceable and may not be functionaland available for service immediately after a flood.Figure 2-21:Medical records saturatedby floodwatersSource: Hancock MedicalCenterMAKING CRITICAL FACILITIES SAFE FROM Flooding2-53

Figure 2-22:Kitchen appliances andequipment from PortSulphur High School weredisplaced and damagedby Hurricane Katrinafloodwaters (2005).2-54 MAKING CRITICAL FACILITIES SAFE FROM Flooding

2.3 REQUIREMENTS AND BESTPRACTICES IN SPECIAL HAZARDAREAS2.3.1 RISK REDUCTION IN “A ZONES”Flood hazard areas designated as A Zones on FIRMs are areaswhere significant wave action is not expected (see Section2.1.1.2). A Zones are found along riverine bodies of water(rivers, streams, creeks, etc.), landward of V Zones, and on someopen coastlines that do not have mapped V Zones. When constructinga critical facility on a site affected by an A Zone flood hazard, sitedesign is influenced by several constraints, such as the presence offlood hazard areas, wetlands, poor soils, steep slopes, sensitive habitats,mature tree stands, and the environmental requirements set bythe various regulatory authorities and the agency that approves developmentplans.Four aspects of the design of flood-resistant buildings and sites aredescribed in this section: site modifications, elevation considerations,flood-resistant materials, and floodproofing considerations.Section 2.3.5 addresses related facilities, including access roads,utility installations, water and wastewater systems, storage tanks,and accessory structures.2.3.1.1 Site ModificationsWhen sites being considered for critical facilities are affected byflood hazards, planners and designers may want to evaluate thefeasibility of certain site modifications in order to provide an in-MAKING CRITICAL FACILITIES SAFE FROM Flooding2-55

Site modifications are not appropriatein floodways along riverine waterways,where obstructions to flows can increaseflood elevations. Engineering analyses arerequired to determine the impact of suchmodifications.creased level of protection to buildings. Theevaluations involve engineering analyses todetermine whether the desired level of protectionis cost-effective, and whether theproposed site modifications alter the floodplainin ways that could increase flooding.The effectiveness of typical site modificationsand their ramifications must be examined foreach specific site.Earthen fill: Fill can be placed in the flood hazard area for the purposeof elevating a site above the design flood elevation. If the fillis placed and compacted so as to be stable during the rise and fallof floodwaters, and if the fill is protected from erosion, then modifyinga site with fill to elevate a facility is preferred over othermethods of elevation. Not only will buildings be less exposed toflood forces, but, under some circumstances (such as long durationfloods), critical facilities may be able to continue to function.Whether nonstructural fill is placed solely to modify the site, orstructural fill is placed for the purpose of elevating buildings,placement of fill can change flooding characteristics, includingincreased flooding on other properties. Engineering analysescan be conducted to determine whether eliminating floodplainstorage by filling will change the direction of the flow of water,create higher flow velocities, or increase the water surface elevationin other parts of the floodplain. Fill is a less effective elevationmethod in flood hazard areas exposed to wave action, such as thebanks of wide rivers, back bays, or Coastal A Zones, because waveaction may erode the fill and adequate armoring or other protectionmethods can be expensive.Excavation: Excavation alone rarely results in significantly alteringthe floodplain on a given parcel of land. Excavation that modifiesa site is more commonly used in conjunction with fill in order tooffset or compensate for the adverse impacts of fill.Earthen levee: A levee is a specially designed barrier that modifiesthe floodplain by keeping the water away from certain areas (seeFigure 2-23). Levees are significant structures that require detailed,site-specific geotechnical investigations; engineering analyses toidentify whether flooding will be made worse on other properties;structural and site design to suit existing constraints; design of in-2-56 MAKING CRITICAL FACILITIES SAFE FROM Flooding

terior drainage (on the land side); and long-term commitment formaintenance, inspection, and repairs. It is important to rememberthat areas behind levees are protected only up to a certain designflood level—once overtopped or breeched, most levees failand catastrophic flooding results. Levees that protect critical facilitiesusually are designed for at least the 0.2-percent-annual-chanceflood (500-year) and have freeboard to increase the factor of safety.Figure 2-23:Schematic of typicalearthen levee andpermanent floodwallFloodwall: Floodwalls are similar to levees in that they provide protectionto certain areas (see Figure 2-23). Failure or overtoppingof a floodwall can result in catastrophic flooding. A floodwall is asignificant structure that is designed to hold back water of a certaindepth based on the design flood for the site. Generally, due todesign factors, floodwalls are most effective in areas with relativelyshallow flooding and minimal wave action. As with levees, designsmust accommodate interior drainage on the land side, and maintenanceand operations are critical for adequate performance.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-57

Floodwalls that protect essential and critical facilities usually aredesigned for the 0.2-percent-annual-chance flood (500-year) andhave freeboard to increase the factor of safety.2.3.1.2 Elevation ConsiderationsThe selection of the appropriate method“Lowest floor” is the floor of the lowestof elevating a critical facility in an A Zoneenclosed area (including the basement). flood hazard area depends on many factors,An unfinished or flood-resistant enclosure, including cost, level of safety and propertyusable solely for parking of vehicles,protection determined as acceptable risk, natureof the flood hazard area, and others.building access, or storage in an areaother than a basement, is not the lowest Methods of elevation are described below.floor, provided the enclosure is built in The minimum elevation requirement is thatcompliance with applicable requirements. the lowest floor (including the basement)must be at or above the DFE (plus freeboard,if desired or required). Table 2-1 in Section2.1.3.4 summarizes the elevation requirements in ASCE 24. Giventhe importance of critical facilities, elevation of the lowest floor toor above the 0.2 percent-annual-chance flood (500-year) elevationis crucial.For elevation methods other than fill, theASCE 7 outlines methods to determine area under elevated buildings in A Zonesdesign loads and load combinations in may be used only for limited purposes:flood hazard areas, including hydrostatic parking, building access, and limited storageloads, hydrodynamic loads, wave(crawlspaces are treated as enclosures, seeloads, and debris impact loads. ASCE below). Owners and designers are cautioned24 addresses design requirements forthat enclosures below the design flood elevationare exposed to flooding and thestructures in flood hazard areas.contents will be damaged or destroyed byfloodwaters. The walls surrounding an enclosuremust have flood openings that areintended to equalize interior and exterior water levels duringrising and falling flood conditions, to prevent differential hydrostaticpressures that could lead to structural damage. Theenclosed area must not contain utilities and equipment (includingductwork) below the required elevation.2-58 MAKING CRITICAL FACILITIES SAFE FROM Flooding

Slab-on-grade foundation on structural fill: Thisis considered to be the safest method to elevatea building in many flood hazard areas,except those where waves and high velocityflows may cause erosion. Structuralfill can be placed so that, when water risesup to the DFE, it will not touch the building(see Figure 2-24) and building access ismaintained. The fill must be designed tominimize adverse impacts, such as increasing flood elevations onadjacent properties, increasing erosive velocities, and causing localdrainage problems. To ensure stability, especially as floodwaters recedeand the soils drain, fill must be designed for the anticipatedwater depths and duration. A geotechnical engineer or soil scientistmay need to examine underlying soils to determine if thebearing capacity is sufficient to carry the added weight of fill, orif consolidation over time may occur. In addition, the effects oflong-term compaction of the fill should be considered, and mayprompt additional elevation as a factor of safety. The horizontalextent of fill from the foundation should be designed to facilitateaccess by emergency and fire vehicles, with a minimum 25-footwidth recommended. Designers are cautioned to avoid excavatinga basement into fill without added structural protection (andcertification that the design meets requirements for dry floodproofing),due to the potential for significant hydrostatic loadsand uplift on basement floors.Communities may require a registereddesign professional to certify that buildingselevated on fill are reasonably safe fromflooding. FEMA NFIP Technical Bulletin10 (2001) discusses criteria for thiscertification.Figure 2-24:Municipal buildingelevated on fillFillMAKING CRITICAL FACILITIES SAFE FROM Flooding2-59

Stem wall foundations: Stem wall foundations have a continuousperimeter grade beam, or perimeter foundation wall, that is backfilledwith compacted earth to the underside of the concrete floorslab (see Figure 2-25). Because this foundation type is backfilledand has no crawlspace, hydrostatic pressures are minimized. Stemwall foundations are designed to come in contact with floodwaterson the exterior. They are more stable than perimeter wall foundationswith crawlspaces, but could experience structural damage ifundermined by local scour and erosion. Designs must account foranticipated debris and ice impacts, and incorporate methods andmaterials to minimize impact damage.Figure 2-25:Typical stem wallfoundationColumns or shear wall foundations (open foundations): Open foundationsconsist of vertical load bearing members (columns, piers, pilings,and shear walls) without solid walls connecting the vertical members.Open foundations minimize changes to the floodplain andlocal drainage patterns, and the area under the building can beused for parking or other uses (see Figure 2-26). The design ofthe vertical members must also account for hydrodynamic loads2-60 MAKING CRITICAL FACILITIES SAFE FROM Flooding

and debris and ice impact loads. Flood loads on shear walls are reducedif they are oriented parallel to the anticipated direction offlow. Erodible soils may be present and local scour may occur; bothmust be accounted for in designs by extending the load-bearingmembers and foundation elements well below the expected scourdepth. Depending on the total height of the elevated facility, thedesign may need to take into consideration the increased exposureto wind and uplift, particularly where breaking waves are expected.Figure 2-26:School elevated oncolumnsContinuous perimeter walls (enclosed foundations with crawlspace):Unlike stem wall foundations, continuous perimeter walls enclosean open area or crawlspace (see Figure 2-27). The perimeter wallsmust have flood openings that are intended to equalize interiorand exterior water levels automatically during changing floodconditions to prevent differential hydrostatic pressures that couldlead to structural damage. Flood openings may be engineeredand certified for the required performance level, or must meetprescriptive requirements (notably, the opening must provideat least 1 square inch of net open area for each square foot ofarea enclosed). Perimeter wall design must also account forhydrodynamic loads, and debris and ice impact loads. Enclosedcrawlspaces must not contain utilities or equipment (includingductwork) below the required elevation. Designers must provideadequate underfloor ventilation and subsurface drainage tominimize moisture problems after flooding.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-61

Figure 2-27:Typical crawlspace withflood openingsPier supports for manufactured and portable units: Manufacturedbuildings and portable units must be elevated above the DFE(plus freeboard, if required). Pier supports must account for hydrodynamicloads and debris and ice impact loads and units mustbe anchored to resist wind loads. Although written specificallyfor manufactured housing units, FEMA 85, Manufactured HomeInstallation in Flood Hazard Areas, has useful information that is applicableto portable units.2.3.1.3 Flood-Resistant MaterialsAll structural materials, nonstructural (finish) materials, and connectorsthat are used below certain elevations (see Table 2-2)should be flood-resistant. Flood-resistant materials have sufficientstrength, rigidity, and durability to adequately resist flood loadsand damage due to saturation. They are building materials that2-62 MAKING CRITICAL FACILITIES SAFE FROM Flooding

are capable of withstanding direct and prolongedcontact with floodwaters withoutsustaining any damage that requires morethan cosmetic repair. As defined in ASCE24, the term “prolonged contact” means partialor total inundation by floodwaters for 72hours for non-coastal areas (fresh water) or12 hours for coastal areas.FEMA NFIP Technical Bulletin FIA-TB-2,Flood-Resistant Materials Requirements,provides some additional information.Many types of materials and applicationproducts are classified by degrees ofresistance to flood damage.In general, materials that are exposed to floodwaters are to becapable of resisting damage, deterioration, corrosion, or decay.Typical construction materials range from highly resistant to notat all resistant to water damage. FEMA NFIP Technical BulletinFIA-TB-2 contains tables with building materials, classified basedon flood resistance (Table 2-2).In areas away from the coast, exposed structural steel shouldbe primed, coated, plated, or otherwise protected against corrosion.Secondary components such as angles, bars, straps, andanchoring devices, as well as other metal components (plates,connectors, screws, bolts, nails angles, bars, straps, and thelike) should be stainless steel or hot-dipped galvanized afterfabrication.Table 2-2: Classes of Flood-Resistant MaterialsNFIP Class Class DescriptionAcceptableUnacceptable5432Highly resistant to floodwater damage. Materials in this class are permitted forpartially enclosed or outside uses with essentially unmitigated flood exposure.Resistant to floodwater damage. Materials in this class may be exposed toand/or submerged in floodwaters in interior spaces and do not require specialwaterproofing protection.Resistant to clean water damage. Materials in this class may be submerged inclean water during periods of intentional flooding.Not resistant to water damage. Materials in this class require essentially dryspaces that may be subject to water vapor and slight seepage.1 Not resistant to water damage. Materials in this class require dry conditions.Source: From U.S. Army Corps of Engineers, FloodProofing Regulations (1995).MAKING CRITICAL FACILITIES SAFE FROM Flooding2-63

Concrete and masonry that are designed and constructed in compliancewith applicable standards are generally considered to beflood-resistant. However, masonry facings are undesirable finishesunless extra anchoring is added to prevent separation (see Figure2-28). Wood and timber members exposed to flood waters shouldbe naturally decay resistant species or pressure treated with appropriatepreservatives.Structural steel and other metal components exposed to corrosionshould be stainless steel or hot-dipped galvanized after fabrication.Figure 2-28:Brick facing separatedfrom the masonry wall atPort Sulpher High School,LA.2.3.1.4 Dry Floodproofing ConsiderationsDry floodproofing involves a combination of design and specialfeatures that are intended to prevent the entry of water into abuilding and its utilities while also resisting flood forces. It involvesstructural reinforcement so that exterior walls are sufficiently robustto withstand the loads described in Section 2.1.2 (hydrostatic2-64 MAKING CRITICAL FACILITIES SAFE FROM Flooding

pressure, hydrodynamic loads, wave loads,and debris impact loads). Exterior walls mustalso be designed to prevent infiltration andseepage of water, whether through the wallitself or through any openings, includingwhere utility lines penetrate the envelope.Floodproofed buildings constructed onpermeable soils require additional designattention, because they are susceptible to hydrostaticpressure from below.According to the NFIP regulations, nonresidentialbuildings and nonresidentialportions of mixed-use buildings may be dryfloodproofed. Areas used for living andsleeping purposes in health care facilitiesand dormitory rooms at fire stations maynot be dry floodproofed. Although floodproofingof the nonresidential spaces isallowed, careful consideration must be given to the possible riskto occupants and additional physical damage.All flood protection measures are designed for certain flood conditions.Therefore, there is some probability that the design willbe exceeded (i.e., water will rise higher than accounted for in thedesign). When this happens to a dry floodproofed building, theconsequences can be catastrophic. As a general rule, dry floodproofingis a poor choice for new critical facilities when avoidanceof the floodplain or elevation methods to raise the building abovethe flood level can be applied. Floodproofing may be acceptablefor retrofitting existing buildings under certain circumstances (seeSection 2.4.4).A number of dry floodproofing limitations and requirements arespecified in ASCE 24:m Dry floodproofing is limited to areas where flood velocities atthe site are less than or equal to 5 feet per second.m If human intervention is proposed, such as measures toprotect doors and windows, the flood warning time shall be aminimum of 12 hours unless the community operates a floodCommunities that participate in the NFIPwill require that a registered professionalengineer or architect develop or review thestructural design, specifications, and plans,and certify that the dry floodproofingdesign and methods of construction to beused are in accordance with acceptedstandards of practice. The standards ofpractice require that the building, togetherwith attendant utility and sanitary facilities,be designed so that it is watertight, withwalls substantially impermeable to thepassage of water and with structuralcomponents having the capability ofresisting hydrostatic and hydrodynamicloads and effects of buoyancy associatedwith the design flood event.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-65

warning system and implements a notification procedure thatprovides sufficient time to undertake the measures requiringintervention.m At least one door satisfying building code requirements for anexit door or primary means of escape must be provided abovethe level of protection.m An emergency plan, approved by the community andposted in at least two conspicuous locations, is required infloodproofed buildings; the plan is to specify the locationof panels and hardware, methods of installation, conditionsthat activate deployment, a schedule for routine maintenanceof any aspect that may deteriorate over time, and periodicpractices and drills.Windows and doors that are below the flood level used for dryfloodproofing design present significant potential failure points.They must be specially designed units (see Figure 2-29) or befitted with gasketed, mountable panels that are designed forthe anticipated flood conditions and loads. Generally speaking,it is difficult to protect window and door openings from watermore than a few feet deep. The framing and connections mustbe specifically designed for these protective measures, or waterpressure may cause window and door frames to separate fromthe building.The documents Flood ResistantDesign and Construction (ASCE 24-05), Flood Proofing: How to EvaluateYour Options (USACE, 1993), FloodProofing Regulations (USACE, 1995),Floodproofing Non-Residential Structures(FEMA 102, 1986), Non-ResidentialFloodproofing – Requirements andCertification (FIA-TB-3 [FEMA NFIP, 1993]),Flood Proofing Systems & Techniques(USACE, 1984) provide additionalinformation about floodproofing.Dry floodproofing is required to extend to 1or 2 feet above the BFE (see Table 2-1). Forthe purpose of obtaining NFIP flood insurance,the floodproofing must extend at least1 foot above the BFE, or the premiums willbe very high. Therefore, a higher level ofprotection is recommended.Floodproofing techniques are consideredto be permanent measures if they are alwaysin place and do not require any specifichuman intervening action to be effective.Use of contingent floodproofing measuresthat require installation or activation, suchas window shields or inflatable barriers,2-66 MAKING CRITICAL FACILITIES SAFE FROM Flooding

may significantly reduce the certainty thatDry floodproofed critical facilitiesfloodproofing will be effective. Rigorous adherenceto a periodic maintenance planmust never be considered safe foroccupancy during periods of high water;is critical to ensure proper functioning.floodproofing measures are intended onlyThe facility must have a formal, writtento reduce physical damage.plan, and people responsible for implementingthe measures must be informedand trained. These measures also dependon the timeliness and credibility of the warning. In addition,floodproofing devices often rely on flexible seals that requireperiodic maintenance and that, over time, may deteriorate andbecome ineffective. Therefore, a maintenance plan must be developedand a rigorous annual inspection and training must beconducted.Figure 2-29:Permanent watertightdoors for deep waterSOURCE: PRESRAY CORPORATIONMAKING CRITICAL FACILITIES SAFE FROM Flooding2-67

Safety of occupants is a significant concern with dry floodproofedbuildings. Regardless of the degree of protectionprovided, dry floodproofed buildings should not be occupiedduring flood events, because failure or overtopping of the floodproofingmeasures is likely to cause catastrophic structuraldamage. When human intervention is required, the people responsiblefor implementing those measures remain at risk whileat the building, even if a credible warning system is in place, becauseof the many uncertainties associated with predicting theonset of flood conditions.2.3.2 RISK REDUCTION IN “V ZONES”Flood hazard areas designated as “V Zones” on FIRMs are relativelynarrow areas along open coasts and lake shores where thebase flood conditions are expected to produce 3-foot or higherwaves. V Zones, sometimes called coastal high hazard areas or specialflood hazard areas subject to high-velocity wave action, arefound on the Pacific, Gulf, and Atlantic coasts, and around theGreat Lakes.Every effort should be made to locate critical facilities outside ofV Zones, because the destructive nature of waves makes it difficultto design a building to be fully functional during and after a floodevent. This is particularly true in coastal areas subject to hurricanesurge flooding (see Section 2.3.4). However, when a decision ismade to build a critical facility in a V Zone or Coastal A Zone, thecharacteristics of the site and the nature of the flood hazards mustbe examined prior to making important design decisions.Beach front areas with sand dunes pose special problems. Manmadealterations of sand dunes are not allowed unless analysesindicate that such modifications will not increase potential flooddamage. The site modifications described in Section 2.3.1.1 thatmay be used in some A Zones to reduce flood hazards generallyare not feasible in V Zones because of wave forces and potentialerosion and scour. In particular, structural fill is not allowed as ameans to raise a building site above the flood level.The NFIP and ASCE 24 do not allow use of dry floodproofingmeasures to protect nonresidential structures in V Zones.2-68 MAKING CRITICAL FACILITIES SAFE FROM Flooding

2.3.2.1 Elevation ConsiderationsThe selection of the appropriate method ofelevating a critical facility in a V Zone floodhazard area depends on many factors, includingcost, desired level of safety andproperty protection, and the nature of theflood hazard area. The NFIP regulations andthe building codes require the elevation ofthe bottom of the lowest horizontal structuralmember of the lowest floor (includingbasement) to be at or above the DFE (plusfreeboard, where required). Given the importanceof critical facilities, elevation to orabove the 0.2-percent-annual-chance flood(500-year) elevation is appropriate andstrongly recommended.Buildings in V Zones must be elevated usingopen foundations, which consist of verticalload bearing members (columns, piers, pilings,and shear walls) without solid walls connecting the verticalmembers. The design of the vertical members must also accountfor hydrodynamic loads and debris impact loads. Flood loads onshear walls are reduced if the walls are oriented parallel to the anticipateddirection of flow. Since erodible soils may be present andlocal scour may occur, both conditions must be accounted for indesigns of load-bearing members and foundations.The area under elevated buildings in V Zones may be used onlyfor limited purposes: parking, building access, and limited storage.Owners and designers are cautioned that enclosures below theDFE are exposed to flooding. Areas under elevated buildings maybe open or enclosed by lattice walls or screening. However, if areasare enclosed by solid walls, the walls must be specifically designedto break away under certain flood loads to allow the free passageof floodwaters under the building. Breakaway walls are non-loadbearing walls, i.e., they do not provide structural support for thebuilding. They must be designed and constructed to collapseunder the impact of floodwaters in such a way that the supportingfoundation system and the structure are not affected.Communities that participate in the NFIPwill require that a registered professionalengineer or architect develop or reviewthe structural design, specifications, andplans, and certify that the design andmethods of construction to be used arein accordance with accepted standardsof practice. The standards of practicerequire that the foundation and structureattached thereto is anchored to resistflotation, collapse, and lateral movementdue to the effects of wind and water loadsacting simultaneously on all buildingcomponents. Water loading values shallbe those associated with the base floodconditions, and wind loading values shallbe those required by applicable State orlocal building codes and standards.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-69

2.3.2.2 Flood-Resistant MaterialsSection 2.3.1.3 addresses the general requirement that all structuralmaterials, nonstructural (finish) materials, and connectorsthat are used below certain elevations are to be flood-resistant materials.In coastal areas, airborne salt aerosols and inundation withsaline water increase the potential for corrosion of some metals.Structural steel and other metal components that are exposed tocorrosive environments should be stainless steel or hot-dipped galvanizedafter fabrication.2.3.3 RISK REDUCTION IN “COASTAL AZONES”Coastal A Zones are areas of the mapped floodplain wherebreaking waves that are between 1.5 to 3 feet high are expectedunder base flood conditions. Coastal A Zones are part of the areashown as the A Zone on a FIRM, landward of the mapped V Zoneor landward of open coasts that do not have a V Zone. FIRMs donot distinguish between Coastal A Zones and A Zones. Designersshould determine whether Coastal A Zone conditions are likely tooccur at a critical facility site because of the anticipated wave actionand loads. This determination is based on an examination ofthe site and its surroundings, the actual surveyed ground elevations,and the predicted stillwater elevations found in the FloodInsurance Study.Coastal A Zones are present where two conditions exist: where theexpected floodwater depth is sufficient to support waves 1.5 to 3feet high, and where such waves can actually occur (see Figure 2-30). The first condition occurs where stillwater depths (verticaldistance between the stillwater elevation and the ground) aremore than 2 feet deep. The second condition occurs where thereare few obstructions between the shoreline and the site. The stillwaterdepth requirement is necessary, but is not sufficient by itselfto warrant designation as a Coastal A Zone, because obstructionsin the area may block wind and dampen waves. Obstructions thatmay dampen waves include buildings, locally high ground, anddense tree stands.2-70 MAKING CRITICAL FACILITIES SAFE FROM Flooding

Figure 2-30:Flood hazard zones incoastal areasField observations and laboratory researchhave determined that floodingAlthough the NFIP regulations and the modelbuilding codes allow dry floodproofing ofwith breaking waves between 1.5 and 3nonresidential buildings in flood hazard areasfeet high produces more damage thanwhere waves are predicted to be betweenflooding of similar depths without waves.1.5 and 3 feet during the base flood (calledTherefore, ASCE 24 specifically requiresCoastal A Zones), designers are cautioned toapplication of the NFIP’s V Zone designfully consider the additional forces associatedrequirements in Coastal A Zones. Sectionwith wave impacts, which may make dry2.3.2.1 addresses elevation requirementsfloodproofing a less feasible alternative.and foundation types, and Section 2.3.2.2addresses flood-resistant materials, usedin V Zones and Coastal A Zones. Thedesigners are advised to pay special attention to two additionalconsiderations:m Debris loads may be significant in Coastal A Zones landward ofV Zones where damaged buildings, piers, and boardwalks canproduce battering debris. Foundations designed to account fordebris loads will minimize damage.m Especially in high wind regions, designers must pay specialattention to the entire roof-to-foundation load path whendesigning and specifying connections. If designed to meetV Zone requirements, designs for buildings in Coastal AZones will account for simultaneous wind and flood forces.Corrosion-resistant connections are especially important forthe long-term integrity of the structure.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-71

2.3.4 RISK REDUCTION IN HURRICANESTORM SURGE AREASCoastal communities along the Atlantic and Gulf coasts are subjectto storm surge flooding generated by hurricanes and tropicalstorms. Depending on a number of variables, storm surge flooddepths may significantly exceed the BFE. In addition, waves arelikely to be larger than predicted for the base flood, and will occurin areas where significant wave action during the base flood is notexpected. Application of the minimum requirements related toelevation of the lowest floor and foundation design does not resultin flood resistance for such extreme conditions. The followingspecial considerations will provide a greater degree of protectionfor critical facilities located in areas subject to storm surges.Higher foundations: Foundations should be designed to elevatethe building so that the lowest horizontal structural members arehigher than the minimum required elevation. Additional elevationnot only reduces damage that results from lower probabilityevents, but the cost of Federal flood insurance is usually lower.However, accessibility may be affected and there will be some additionalconstruction costs that must be balanced against avoidedfuture damage and a higher likelihood that a facility can be morerapidly restored to full function.Scour and erosion: Storm surge flooding and waves can cause scourand erosion, even at locations that are some distance from theshoreline. Foundation designs for critical facilities in coastal communitiesshould account for some erosion and local scour ofsupporting soil during low probability surge events.Water-borne debris: Storm surge flooding can produce large quantitiesof floating debris, even at locations that are some distancefrom the shoreline. Debris damages nonstructural building componentsand, in some cases, prolonged battering can lead tostructural failure. Foundation designs for critical facilities incoastal communities should account for debris loads. This is especiallyimportant where damage to other buildings in the area maygenerate additional debris, thereby increasing the loads.Continuous load path: Especially in high wind regions, designersshould pay special attention to the entire roof-to-foundation load2-72 MAKING CRITICAL FACILITIES SAFE FROM Flooding

path when designing and specifying connections. Connectionsmust be capable of withstanding simultaneous wind and floodforces. Poorly connected buildings may fail or float off of foundationswhen floodwaters and waves are higher than the designflood elevation. Corrosion-resistant connections are critical for thelong-term integrity of the structure, and should be inspected andmaintained periodically.Emergency equipment: Equipment that is required for emergencyfunctioning during or immediately after a storm surge event,such as emergency generators and fuel tanks, is best installed wellabove the design flood elevation.Occupancy of surge-prone areas: Designers and owners should planto use the lowest elevated floor for non-critical uses that, even ifexposed to flooding more severe than the design flood, will notimpair critical functioning during post-flood recovery.2.3.5 RISK REDUCTION FOR RELATEDFACILITIESCritical facilities do not exist as purely independent buildings.They usually are accompanied by a variety of related facilities,such as utility installations both inside and outside of buildings,gas and electric services, water and wastewater services, abovegroundor underground storage tanks, accessory structures andoutbuildings, and access roads and parking lots.2.3.5.1 Access RoadsAccess roads to critical facilities should be designed to provide safeaccess at all times, to minimize impacts on flood hazard areas, tominimize damage to the road itself, and to minimize exposing vehiclesto dangerous situations. Depending on the site and specificflood characteristics, balancing those elements can be difficult.Designers should take the following into consideration.Safety factors: Although a critical facility’s access road may not berequired to carry regular traffic like other surface streets, a floodproneroad always presents a degree of risk to public safety. ToMAKING CRITICAL FACILITIES SAFE FROM Flooding2-73

minimize those risks, some State or local regulatory authorities requirethat access roads be designed so that the driving surface isno more than 1 to 2 feet below the DFE. To maximize evacuationsafety, two separate accesses to different feeder roads are recommended.In some circumstances, especially long-duration floodingwhere a critical facility is built on fill, dry access may allow continuedoperations.Floodplain impacts: Engineering analyses may be required to documentthe effects on flood elevations and flow patterns if largevolumes of fill are required to elevate a road to minimize or eliminateflooding above the driving surface.Drainage structure and road surface design: The placement of multipledrainage culverts, even if not needed for local drainage, can facilitatethe passage of floodwaters and minimize the potential fora road embankment to act as a dam. Alternatively, an access roadcan be designed with a low section over which high water can flowwithout causing damage. Embankments should be designed to remainstable during high water and as waters recede. They should besloped and protected to resist erosion and scour. Similarly, the surfaceand shoulders of roads that are intended to flood should bedesigned to resist erosion. The increased resistance to erosion maybe accomplished by increasing the thickness of the road base.2.3.5.2 Utility InstallationsUtilities associated with new critical facilities in flood hazard areasmust be protected either by elevation or special design and installationmeasures. Utilities subject to this provision include allsystems, equipment, and fixtures, including mechanical, electrical,plumbing, heating, ventilating, and air conditioning. Potablewater systems (wellheads and distribution lines) and wastewatercollection lines are addressed in Section 2.3.5.3.Utility systems and equipment are best protected when elevatedabove the DFE (plus freeboard, if required). In somecases, equipment can be located inside protective floodproofedenclosures, although it must be recognized that flooding that exceedsthe design level of such an enclosure will adversely affectthe equipment (see Figure 2-31). Designers should pay partic-2-74 MAKING CRITICAL FACILITIES SAFE FROM Flooding

ular attention to underfloor utilities andductwork to ensure that they are properlyelevated. Plumbing conduits, water supplylines, gas lines and electric cables that mustextend below the DFE should be located, anchored,and protected to resist the effects offlooding. Equipment that is outside of elevatedbuilding also must be elevated:For more information on utility installations,see Protecting Building Utilities from FloodDamage: Principles and Practices forthe Design and Construction of ResistantBuilding Utility Systems (FEMA 348, 1999).m In A Zones, equipment may be affixed to raised supportstructures or mounted on platforms that are attached to orcantilevered from the primary structure.m In V Zones and Coastal A Zones, equipment may be affixedto raised support structures designed for the flood conditions(waves, debris impact, erosion, and scour) or mounted onplatforms that are attached to or cantilevered from theprimary structure. If an enclosure is constructed under theelevated building, the designer must take care that utilitiesand attendant equipment are not mounted on or pass throughwalls that are intended to break away.Figure 2-31:Equipment room withwatertight doorSOURCE: PRESRAY CORPORATIONMAKING CRITICAL FACILITIES SAFE FROM Flooding2-75

Although it is difficult to achieve, the model building codes andNFIP regulations provide an alternative that allows utility systemsand equipment to be located below the DFE. This alternative requiresthat such systems and equipment be designed, constructed,and installed to prevent floodwaters from entering or accumulatingwithin the components during flood events.2.3.5.3 Potable Water and Wastewater SystemsNew installations of potable water systems and wastewater collectionsystems are required to resist flood damage, includingdamage associated with infiltration of floodwaters and dischargeof effluent. Health concerns arise when water supply systems areexposed to floodwaters. Contamination from flooded sewage systemsposes additional health and environmental risks. Onsitewater supply wellheads should be located on land elevated fromthe surrounding landscape to allow contaminated surface waterand runoff to drain away. Well casings should extend above thedesign flood elevation, and casings should be sealed with a tightfitting,floodproof, and vermin-proof well cap. The space betweenthe well casing and the side of the well must be sealed to minimizeinfiltration and contamination by surface waters.Sewer collection lines should be located and designed to avoid infiltrationand backup due to rising floodwaters. Devices designedto prevent backup are available and are recommended to providean added measure of protection.Onsite sewage systems usually are not used as the primary sewagedisposal system for new critical facilities. However, it would be prudentfor owners, planners, and designers to consider a backuponsite sewage system if a facility’s functionality will be impairedif the public system is affected by flooding. Designers are advisedthat local or State health departments may impose constraints thatlimit or prevent locating septic fields in floodplain soils or withina mapped flood hazard area. If allowed, septic fields should be locatedon the highest available ground to minimize inundation andimpairment by floodwaters. An alternative to a septic field is installationof a holding tank that is sized to contain wastewater fora period of time, perhaps a few days if the municipal system is expectedto be out of service.2-76 MAKING CRITICAL FACILITIES SAFE FROM Flooding

2.3.5.4 Storage Tank InstallationsAboveground and underground storage tanks located in floodhazard areas must be designed to resist flotation, collapse, andlateral movement. ASCE 24 specifies that aboveground tanks areto be elevated or constructed, installed and anchored to resistat least 1.5 times the potential buoyant and other flood forcesunder design flood conditions, assuming the tanks are empty.Similarly, underground tanks are to be anchored to resist atleast 1.5 times the potential buoyant forces under design floodconditions, assuming the tanks are empty. In all cases, designersare cautioned to address hydrodynamic loads and debris impactloads that may affect tanks that are exposed to floodwaters.Vents and fill openings or cleanouts should be elevated abovethe DFE or designed to prevent the inflow of floodwaters or outflowof the contents of tanks.2.3.5.5 Accessory StructuresDepending on the type of accessory structures, full compliancewith floodplain management regulations is appropriate and maybe required. For example, buildings or portable classrooms thatserve educational purposes (e.g., offices, classrooms), even if detachedfrom the primary school building, are not considered tobe accessory in nature and must be elevated and protected to thesame standards as other buildings.Some minor accessory structures need not fully comply, but maybe “wet floodproofed” using techniques that allow them to floodwhile minimizing damage. Examples include small storage sheds,garages, and restrooms. Accessory structures must be anchoredto resist flotation, collapse, and lateral movement. Flood-resistantmaterials must be used and utilities must be elevated abovethe DFE (plus freeboard, if required). Openings in walls must beprovided to allow the free inflow and outflow of floodwaters tominimize the hydrostatic loads that can cause structural damage.Because wet floodproofed accessory buildings are designed toflood, critical facility staff must be aware that contents will bedamaged.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-77

2.4 RISK REDUCTION FOR EXISTINGCRITICAL FACILITIESOwners and operators of public and notfor-profitcritical facilities should be awareof the importance of flood insurancecoverage for facilities that are located inthe flood hazard areas shown on NFIPmaps. If not insured for flood peril, theamount of flood insurance that shouldhave been in place will be deducted fromany Federal disaster assistance paymentthat would otherwise have been madeavailable. A particular facility may have toabsorb up to $1 million in unreimbursedflood damage per building, becausethe NFIP offers $500,000 in buildingcoverage and $500,000 in contentscoverage for nonresidential buildings(coverage limits as of early 2006).2.4.1 IntroductionSection 2.2.2 describes the type of damage that can besustained by critical facilities that already are located inflood hazard areas. The vulnerability of these facilitiescan be reduced if they can be made more resistant to flood damage.Decisionmakers may take such action when flood hazardsare identified and there is a desire to undertakerisk reduction measures proactively.Interest may be prompted by a flood or bythe requirement to address flood resistanceas part of proposed substantial improvementor an addition. Some questions andguidance intended to help identify buildingcharacteristics of importance when consideringrisk reduction measures for existingfacilities are included in the checklist inSection 2.5.Work on existing buildings and sites is subjectto codes and regulations, and theappropriate regulatory authority with jurisdictionshould be consulted. With respectto reducing flood risks, work generally fallsinto the categories described in the followingsubsections.2-78 MAKING CRITICAL FACILITIES SAFE FROM Flooding

2.4.2 SITE MODIFICATIONSA plan to modify the site of an existing facility that is subject toflooding requires careful examination by an experienced professionalengineer. Determining the suitability of a specific measurerequires a complex evaluation of many factors, including the natureof flooding and the nature of the site. The first part of Table2-3 in Section 2.5 identifies elements that influence the choiceof mitigation measures applicable to existing sites. Some floodcharacteristics may make it infeasible to apply site modificationmeasures to existing facilities (e.g., depths greater than 3 to 4 feet,very high velocities, insufficient warning because of flash floodingor rapid rate of rise, and very long duration).A common problem with all site modifications is the matter ofsite access. Depending on the topography of the site, constructionof barriers to floodwaters may require special access points.Access points may be protected with manually installed stop-logsor designed gates that drop in, slide, or float into place. Whetheractivated by automatic systems or manually operated, access protectionrequires sufficient warning time.Other significant constraining factors include poor soils and insufficientland area which can make site modifications eitherinfeasible or very costly. A critical facility may be among severalbuildings and properties that can be protected, increasing thebenefits. For any type of barrier, rainfall that collects on the landside must be accounted for in the design, whether through adequatelysized stormwater storage basins constructed on land setaside for this purpose, or by providing large-capacity pumps tomove collected water to the water side of the barrier.Each of these site modification measures described below has limitations,including the fact that floods larger than the design floodwill exceed the level of protection.Regrading the site (berm): Where a facility is exposed to relativelyshallow flooding and sufficient land area is available, regradingthe site or constructing an earthen berm may provide adequateprotection.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-79

Earthen levee: Earthen levees are engineered structures that are designedto keep water away from land area and buildings. Hydraulicanalyses and geotechnical investigations are required to determinetheir feasibility and effectiveness. For existing sites, constraints includethe availability of land (levees have a large “footprint” andrequire large land areas), cost (including availability of suitable fillmaterial and long-term maintenance), and difficulties with site access.Levees are rarely used to protect a single site, although theymay offer a reasonable solution for a group of buildings. Locatinglevees and floodwalls within a designated floodway is generallynot allowed. Rapid onset flooding makes it impractical to design aflood levee with access points that require installation of a closuresystem. Earthen levees may also be subject to high velocity flowsthat cause erosion and affect their stability.Permanent floodwall: Floodwalls are freestanding, permanent engineeredstructures that are designed to prevent encroachment offloodwaters. Typically, a floodwall is located some distance from abuilding, so that structural modification of the existing buildingis not required. Floodwalls may protect only the low side of a site(in which case they must “tie” into high ground) or completelysurround a site (which may affect access because special closurestructures are required and must be installed before the onset offlooding, see Figure 2-32).Figure 2-32:A masonry floodwallwith multiple engineeredopenings protected theOak Grove LutheranSchool in Fargo, ND fromflooding in 2001.SOURCE: Flood CentralAmerica, LLC2-80 MAKING CRITICAL FACILITIES SAFE FROM Flooding

Mobilized floodwall: This category of flood protection measuresincludes fully engineered flood protection structures that havepermanent features (foundation and vertical supports) and featuresthat require human intervention when a flood is predicted(horizontal components called planks or stop-logs). Mobilizedfloodwalls have been used to protect entire sites, or to tie into permanentfloodwalls or high ground. Because of the manpower andtime required for proper placement, these measures are bettersuited to conditions that allow long warning times.2.4.3 ADDITIONSAll model building codes generally treat additions as new constructionand require additions to critical facilities in flood hazardareas to be elevated or dry floodproofed to minimize exposureto flooding. However, full compliance with the code and NFIPrequirements is only required if an addition is a substantial improvement(i.e., the cost of the addition plus all other work equalsor exceeds 50 percent of the market value ofthe building). Designers are cautioned thatexisting buildings as well may be required tobe brought into compliance with the floodresistantprovisions of the code or localordinances if the addition is structurally connectedto the existing building.Section 2.3.1.2 outlines elevation options that are applicableto additions in A Zones (see Section 2.3.2.1 for elevation considerationsapplicable to additions in V Zones). Elevation of anaddition on fill may not be feasible unless structural fill can beplaced adjacent to the existing building. Utility service equipmentfor additions must meet the requirements for new installations(see Section 2.3.5.2).With respect to code compliance and designing additions to resistflood damage, one of the more significant issues that maycome up is ease of access. If the lowest floor of the existing facilityis below the DFE, steps, ramps, or elevators will be required forthe transition to the new addition. Some jurisdictions may wishto allow variances to the requirement for elevation, because alternativemeans of access are available, such as ramps and elevators.For more information on additions andsubstantial improvements, see Answers toQuestions About Substantially DamagedBuildings (FEMA 213, 1991).MAKING CRITICAL FACILITIES SAFE FROM Flooding2-81

Under the regulations of the NFIP and FEMA guidance, it is notconsidered appropriate to grant such a variance.2.4.4 REPAIRS, RENOVATIONS, ANDUPGRADESEvery critical facility that is considered for upgrades and renovations,or that is being repaired after substantial damage from anycause, must be examined for structural integrity and stability todetermine compatibility with structural modifications that may berequired to achieve acceptable performance. When an existing facilityis located in a flood hazard area, that examination shouldinclude consideration of measures to resist flood damage and reducerisks.The model building codes and the regulations of the NFIP requirethat work constituting “substantial improvement” of anexisting building be in compliance with the flood-resistant provisionsof the code. Non-substantial improvements should take intoaccount measures to reduce future flood damage, such as thosedescribed in Section 2.4.8, and wet floodproofing measures thatallow water to enter the building to avoid structural damage, aswell as emergency measures (see Section 2.4.9).Additional information on rehabilitationof existing buildings is provided inFlood Proofing: How to Evaluate YourOptions (USACE, 1993), FloodproofingNon-Residential Structures (FEMA 102),Floodproofing—Requirements andCertification (FIA-TB-3), and EngineeringPrinciples and Practices for RetrofittingFlood-prone Buildings (FEMA 259,1995). Although written primarily forhomes, this last reference contains verydetailed checklists and worksheets thatcan be modified. They also provide someguidance for evaluating the costs andbenefits of various measures.Compliance with flood-resistant provisionsmeans the existing building must be elevatedor dry floodproofed. Both options can be difficultfor existing critical facilities, given thetypical use, size, and complexity of some ofthese buildings. Retrofit dry floodproofing(described in Section 2.4.5) is generally limitedto water depths of 3 feet or less, unlessthe structural capacity of the buildings havebeen assessed by a qualified design professionaland found to be capable of resistingthe anticipated loads.Elevating an existing building presents anentirely different set of challenges and alsorequires detailed structural engineeringanalyses. It involves the same equipment and2-82 MAKING CRITICAL FACILITIES SAFE FROM Flooding

methods used to move other types of buildings; expert buildingmovers have successfully moved large, heavy, and complexbuildings, sometimes by segmenting them. A critical facility that iselevated in-place must meet the same performance standards setfor new construction.2.4.5 RETROFIT DRY FLOODPROOFINGModification of an existing building may“Dry floodproofing” refers to measures andbe required or desired in order to addressmethods to render a building envelopeexposure to design flood conditions. Modificationsthat may be considered includesubstantially impermeable to floodwater.construction of a reinforced supplementarywall, measures to counter buoyancy(especially if there is below-grade space), installation of specialwatertight door and window barriers (see Figure 2-33), and providingwatertight seals around the points of entry of utility lines.The details of structural investigations and structural design ofsuch protection measures are beyond the scope of this manual.Figure 2-33:Boulder CommunityHospital, Boulder, COinstalled this permanentlymounted floodgate ina low floodwall; thefloodgate swings to the leftto close off the door thatleads to the mechanicalequipment room.Because of the tremendous flood loads that may be exerted ona building not originally designed for such conditions, detailedstructural engineering evaluations are required to determineMAKING CRITICAL FACILITIES SAFE FROM Flooding2-83

whether an existing building can be dry floodproofed. The followingelements must be examined:m The strength of the structural systemm Whether non-load bearing walls can resist anticipated loads; secondarywalls can be constructed immediately adjacent to existingwalls, with a waterproof membrane, to provide adequate strengthm The effects of buoyancy on the walls and floors of below-gradeareasm Effective means to install watertight doors and windows, ormountable panelsm Protection where utilities enter the buildingm Methods to address seepage, especially where long-durationflooding is anticipatedm Whether there is sufficient time for human interventionmeasures, given the availability of official warnings ofpredicted flood conditionsApplication of waterproofing products or membranes directly toexterior walls may minimize infiltration of water, although thereare concerns with durability and limitations on use (this measureis most effective for shallow, short-duration flooding). Retrofitmeasures that require human intervention are considered emergencymeasures and are discussed in Section 2.4.9.2.4.6 UTILITY INSTALLATIONSSome aspects of an existing flood-prone critical facility’s utility systemsmay be modified to reduce damage. The effectiveness ofsuch measures depends not only on the nature of the flooding,but the type of utility and the degree of exposure. Table 2-3 in Section2.5 lists some questions that will help facility planners and designersto examine risk reduction measures.2-84 MAKING CRITICAL FACILITIES SAFE FROM Flooding

Even if a facility is unlikely to sustain extensivestructural damage from flooding, highcosts and delayed reoccupancy may resultfrom flood-damaged utility systems. The riskreduction design measures described belowcan be applied, whether undertaken as part oflarge-scale retrofits of existing buildings, or asseparate projects.Additional guidance on improving theflood resistance of utility installations inexisting buildings is found in FEMA 348,Protecting Building Utilities From FloodDamage: Principles and Practices for theDesign and Construction of Flood ResistantBuilding Utility Systems.Relocate from below-grade areas: The most vulnerable utility installationsare those located below grade, and the most effectiveprotection measure is to relocate them to properly elevated floorsor platforms that are at least 2 feet above the DFE. The complexityof rerouting pipes, conduits, ductwork, electrical service, lines,and connections will depend on site-specific factors.Elevate components: Whether located inside or outside of thebuilding, some components of utility systems can be elevatedin-placeon platforms, including electric transformers,communications switch boxes, water heaters, air conditioningcompressors, furnaces, boilers, and heat pumps (see Figure 2-34).Figure 2-34:Elevated utility boxMAKING CRITICAL FACILITIES SAFE FROM Flooding2-85

Anchor tanks and raise openings: Existing tanks can be elevated oranchored, as described in Section 2.3.5.4. If anchored below theDFE, tank inlets, vents, fill pipes, and openings should be elevatedabove the DFE, or fitted with covers designed to prevent the inflowof floodwaters or outflow of the contents of the tanks.Protect components: If utility components cannot be elevated, it maybe feasible to construct watertight enclosures, or enclosures withwatertight seals that require human intervention to install whenflooding is predicted.Elevate control equipment: Control panels, gas meters, and electricalpanels can be elevated, even if the equipment they service cannotbe protected.Separate electrical controls: Where areas within an existing facilityare flood-prone, separation of control panels and electricalfeeders will facilitate shutdown before floodwaters arrive, and helpprotect workers during cleanup.Protect against electrical surges: Current fluctuations and service interruptionsare common in areas affected by flooding. Equipmentand sensitive electrical components can be protected by installingsurge protection and uninterruptible power supplies.Connections for portable generators: Pre-wired portable generatorconnections allow for quick, failure-free connection anddisconnection of the generators when needed for continuedfunctionality.2.4.7 POTABLE WATER AND WASTEWATERSYSTEMSAll plumbing fixtures that are connected to the potable watersystem may become weak points in the system if they allow floodwatersto contaminate the system. Relocating the uses that requireplumbing to elevated floors and removing the fixtures that arebelow the DFE provides protection. Wellheads can be sealed withwatertight casings or protected within sealed enclosures.2-86 MAKING CRITICAL FACILITIES SAFE FROM Flooding

Wastewater system components become sources of contaminationduring floods. Rising floodwaters may force untreated sewage tobackup through toilets. Specially designed back-flow devices canbe installed, or restrooms below the DFE can be provided withoverhead piping that may require specially designed pumps to operateproperly. Septic tanks can be sealed and anchored.2.4.8 OTHER DAMAGE REDUCTIONMEASURESA number of steps can be taken to make existing facilities in floodhazard areas more resistant to flood damage, which also facilitatesrapid recovery, cleanup, and reoccupancy. Whether these measuresare applicable to a specific facility depends, in part, on thecharacteristics of the flood hazard and the characteristics of thebuilding itself. Facility planners and designers should consider thefollowing:m Rehabilitate and retrofit the building envelope with openingsspecifically designed to allow floodwaters to flow in andout to minimize hydrostatic pressure on walls (called wetfloodproofing, see Figure 2-35). Although it allows water toenter the building, this measure minimizes the likelihood ofmajor structural damage. Walls that enclose interior spaceswould also be retrofitted with openings.Figure 2-35:The enclosed entry andstorage area to the rightof the fire truck bayswere retrofitted with floodopenings.SOURCE: SMART VENT, LLCMAKING CRITICAL FACILITIES SAFE FROM Flooding2-87

m Replace interior walls that have cavities with flood-resistantconstruction or removable panels to facilitate cleanup anddrying.m Abandon the use of below-grade areas (basements) by fillingthem in to prevent structural damage.m Permanently relocate high-value or sensitive functions thatare often found on the ground floor of critical facilities (e.g.,offices, records, libraries, and computer laboratories) tohigher floors or elevated additions.m Install backflow devices in sewer lines.m Pre-plan actions to move high-value contents from the lowerfloors to higher floors when a flood warning is issued.m Replace wall, flooring, and finish materials with flood-resistantmaterials.m Use epoxy or other impervious paints on concrete and otherpermeable surfaces to minimize contamination.m Install separate electric circuits and ground fault interruptercircuit breakers in areas that will flood. Emergency measuresshould be provided so that electrical service can be shut downto avoid electrocution hazards.m Relocate chemicals to storage areas not subject to flooding.2.4.9 EMERGENCY MEASURESEmergency response to flooding is outside the scope of thismanual. However, it is appropriate to examine feasible emergencymeasures that may provide some protection. The following discussionpertains only to emergency measures that have been used toreduce flood damage to older buildings that are already locatedin flood hazard areas. These measures do not achieve compliancewith building and life safety codes, they may not provide protectionto occupants, and they can experience a high frequency offailure depending on human factors related to deployment.2-88 MAKING CRITICAL FACILITIES SAFE FROM Flooding

Emergency barriers are measures of “last resort,” and should beused only when a credible flood warning with adequate lead-timeis available and dependable. These measures have varying degreesof success, depending on the available manpower, skillrequired, long-term maintenance of materials and equipment,suitability for site-specific flood conditions, and having enoughadvanced warning. Complete evacuation of protected buildingsis required, as these measures should not be consideredadequate protection for occupants. Furthermore, emergencybarriers are not acceptable in lieu of designed flood resistantprotection for new buildings.Sandbag walls: Unless emergency placement is planned wellin advance or under the direction of trained personnel, mostsandbag barriers are not constructed in accordance with properpractices, leading to leakage and failures. Because of the intensivework effort and length of time required for protection fromeven relatively shallow water, sandbag walls are not a reliableprotection measure. To be effective, sandbags and sand shouldbe stockpiled and checked regularly to ensure that sandbagshave not deteriorated. Sandbags have some other drawbacks,including high disposal costs and their tendency to absorb pollutantsfrom contaminated floodwaters, which necessitatesdisposal as hazardous waste.Water-filled barriers: A number of vendors make water-filled barriersthat can be assembled with relative ease, depending on thesource of water for filling. The barriers must be specifically sizedfor the site. Training and annual drills are important so thatpersonnel know how to place and deploy the barriers. Properstorage, including cleaning after deployment, is necessary toprotect the materials over long periods of time.Panels for doors: For shallow and short-duration flooding, panelsof sturdy material can be made to fit doorways to minimize theentry of floodwaters. Effectiveness is increased significantly if aflexible gasket or sealant is provided, and the mounting hardwareis designed to apply even pressure. Personnel must knowwhere the materials are stored and be trained in their deployment.A number of vendors make special doors for permanentinstallation and drop-in panels or barriers that are designed tobe watertight (see Figure 2-36).MAKING CRITICAL FACILITIES SAFE FROM Flooding2-89

Figure 2-36:Example of an aluminumflood barrier used forflooding less than 3 feetdeep.SOURCE: SAVANNAH TRIMS2-90 MAKING CRITICAL FACILITIES SAFE FROM Flooding

2.5 CHECKLIST FOR BUILDINGVULNERABILITY OF FLOOD-PRONE CRITICAL FACILITIESThe Checklist for Building Vulnerability of Flood-ProneCritical Facilities (Table 2-3) is a tool that can be used tohelp assess site-specific flood hazards and building vulnerability.The checklist is useful during site selection, preliminarydesign of a new building, or when considering rehabilitation of anexisting facility. In addition to examining building design issuesthat affect vulnerability, the checklist also helps users to examinethe functionality of the critical and emergency systems upon whichmost critical facilities depend. The checklist is organized intoseparate sections, so that each section can be assigned to a subjectexpert for greater accuracy of the examination. The results shouldbe integrated into a master vulnerability assessment to guide thedesign process and the choice of appropriate mitigation measures.Table 2-3: Checklist for Building Vulnerability of Flood-Prone Critical FacilitiesVulnerability Sections Guidance ObservationsSite ConditionsIs the site located neara body of water (with orwithout a mapped floodhazard area)? Is the site in aflood hazard area shown onthe community’s map (FIRMor other adopted map)? If so,what is the flood zone?All bodies of water are subject to flooding, butnot all have been designated as a floodplain onFIRMs.Flood hazard maps usually are available forreview in local planning and permit offices.Electronic versions of the FIRMs may be availableonline at www.fema.gov. Paper maps may beordered by calling (800) 358-9616.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-91

Table 2-3: Checklist for Building Vulnerability of Flood-Prone Critical Facilities (continued)Vulnerability Sections Guidance ObservationsSite Conditions (continued)(continued)Is the site affected by aregulatory floodway ?Is the site located in a stormsurge inundation zone (ortsunami inundation area)?What is the DFE (or does ananalysis have to be done todetermine the DFE)? Whatis the minimum protectionlevel required by regulatoryauthorities?Does the FIS or other studyhave information about the500-year flood hazard area?Has FEMA issued postdisasteradvisory floodelevations and maps?(continued)Development in floodways, where floodwaterstypically are fast and deep, must be supportedby engineering analyses.In coastal communities, even sites at somedistance inland from the shoreline may beexposed to extreme storm surge flooding. Stormsurge maps may be available at State or localemergency management offices.Reference the FIS for flood profiles anddata tables. Site-specific analyses should beperformed by qualified engineers.Check with regulatory authorities to determinethe required level of protection.If a major flood event has affected thecommunity, FEMA may have issued newflood hazard information, especially if areasnot shown on the FIRMs have been affected.Sometimes these maps are adopted and replacethe FIRMs; sometimes the new data are advisoryonly.What are the expecteddepths of flooding at thesite (determined using floodelevations and groundelevations)?Has the site been affected bypast flood events? What isthe flood of record?Records of actual flooding augment studiesthat predict flooding, especially if historicevents resulted in deeper or more widespreadflooding. Information may be available fromlocal planning, emergency management, andpublic works agencies, or State agencies, theU.S. Army Corps of Engineers, or the NaturalResources Conservation Service.The flood of record is often a lower probabilityevent (with higher flood elevations) than the 100-year flood.2-92 MAKING CRITICAL FACILITIES SAFE FROM Flooding

Table 2-3: Checklist for Building Vulnerability of Flood-Prone Critical Facilities (continued)Vulnerability Sections Guidance ObservationsSite Conditions (continued)What is the expectedvelocity of floodwaters on thesite?Are waves expected to affectthe site?Is there information on howquickly floodwaters mayaffect the site?What is the expectedduration of flooding?Is there a history of floodrelateddebris problems orerosion on the site?Is the site within an areapredicted to flood if alevee or floodwall fails or isovertopped?Is the site in an areapredicted to be inundatedif an upstream dam were tofail?Velocity is a factor in computing loads associatedwith hydrodynamic forces, including drag onbuilding surfaces. Approximations of velocitymay be interpolated from data in the FISFloodway Data Table if the waterway wasstudied using detailed methods, application ofapproximation methods based on continuity,local observations and sources, or site-specificstudies.Waves can exert considerable dynamic forceson buildings and contribute to erosion and scour.Wind-driven waves occur in areas subject tocoastal flooding and where unobstructed windsaffect wide floodplains (large lakes and majorrivers). Standing waves may occur in riverinefloodplains where high velocities are present.Warning time is a key factor in the safe andorderly evacuation of critical facilities. Certainprotective measures may require adequatewarning so that actions can be taken by skilledpersonnel.Duration has bearing on the stability of earthenfills, access to a site and emergency response,and durability of materials that come into contactwith water. Records of actual flooding are thebest indicator of duration as most floodplainanalyses do not examine duration.Site design should account for deposition ofdebris and sediment, as well as the potentialfor erosion-related movement of the shoreline orwaterway. Buildings exposed to debris impactor undermining by scour and erosion should bedesigned to account for these conditions.Flood protection works may be distant from sitesand not readily observable. Although a lowprobability event, failure or overtopping cancause unexpected and catastrophic damagebecause the protected lands are not regulated asflood hazard areas.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-93

Table 2-3: Checklist for Building Vulnerability of Flood-Prone Critical Facilities (continued)Vulnerability Sections Guidance ObservationsSite Conditions (continued)(continued)The effects of an upstream dam failure arenot shown on the FIRMs or most flood hazardmaps prepared locally. Although dam failuregenerally is considered an unlikely event, thepotential threat should be evaluated due to thecatastrophic consequences. (Note: owners ofcertain dams should have emergency actionplans geared toward notification and evacuationof vulnerable populations and critical facilities.)Does the surroundingtopography contribute to theflooding at the site? Is therea history of local surfacedrainage problems due toinadequate site drainage?If areas with poor local drainage and frequentflooding cannot be avoided, filling, regrading,and installation of storm drainage facilities maybe required.Given the nature ofanticipated flooding andsoils, is scour around andunder the foundation likely?Has water from othersources entered the building(i.e., high groundwater,water main breaks, sewerbackup, etc.)? Is there ahistory of water intrusionthrough floor slabs or wellfloorconnections? Arethere underground utilitysystems or areaways thatcan contribute to basementflooding? Are therestormwater sewer manholesupslope of window areasor openings that allowlocal drainage to enter thebasement/lower floor areas?Scour-prone sites should be avoided, in part dueto likely long-term maintenance requirements.Flooding that is high velocity or accompanied bywaves is more likely to cause scour, especially onfills, or where local soils are unconsolidated andsubject to erosion.These questions pertain to existing facilities thatmay be impaired by water from sources otherthan the primary source of flooding. The entirebuilding envelope, including below-grade areas,should be examined to identify potential waterdamage.2-94 MAKING CRITICAL FACILITIES SAFE FROM Flooding

Table 2-3: Checklist for Building Vulnerability of Flood-Prone Critical Facilities (continued)Vulnerability Sections Guidance ObservationsSite Conditions (continued)Is at least one access roadto the site/building passableduring flood events?Are at-grade parking lotslocated in flood-prone areas?Are below-grade parkingareas susceptible toflooding?Are any portions of thebuilding below the DesignFlood Elevation?Has the building beendamaged in previous floods?Are any building spacesbelow-grade (basements)?Are any critical buildingfunctions occupying spacethat is below the elevationof the 500-year flood or theDesign Flood Elevation?Can critical functions berelocated to upper levels thatare above predicted floodelevations?If critical functions cannot berelocated, is floodproofingfeasible?If critical functions mustcontinue during a floodevent, have power, supplies,and access issues beenaddressed?Access is increasingly important as theduration of flooding increases. For the safety ofoccupants, most critical facilities should not beoccupied during flood events.Areas where vehicles could be affectedshould have signage to warn users of the risk.Emergency response plans should includenotification of car owners.For existing buildings, it is important todetermine which portions are vulnerable inorder to evaluate floodproofing options. If flooddepths are expected to exceed 2 or 3 feet, dryfloodproofing may not be feasible. Alternativesinclude modifying the use of flood-prone areas.Below-grade spaces and their contents aremost vulnerable to flooding and local drainageproblems. Rapid pump out of below-gradespaces can unbalance forces if the surroundingsoil is saturated, leading to structural failure.If below-grade spaces are intended to be dryfloodproofed, the design must account forbuoyant forces.New critical facilities built in flood hazard areasshould not have any functions occupying floodpronespaces (other than parking, buildingaccess and limited storage).Existing facilities in floodplains should beexamined carefully to identify the best options forprotecting functionality and the structure itself.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-95

Table 2-3: Checklist for Building Vulnerability of Flood-Prone Critical Facilities (continued)Vulnerability Sections Guidance ObservationsSite Conditions (continued)Have critical contents(files, computers, servers,equipment, research, anddata) been located on levelsof the facility above the floodelevations?Are critical recordsmaintained off-site?For existing facilities that are already locatedin flood hazard areas, the nature of the facilitymay require continued use of flood-prone space.However, the potential for flooding should berecognized and steps taken to minimize loss ofexpensive equipment and irreplaceable data. Ifcritical contents cannot be permanently locatedon higher floors, a flood response plan shouldtake into account the time and attention neededto move such contents safely.Building EnvelopeAre there existingfloodproofing measures inplace below the expectedflood elevation? What is thenature of these measures andwhat condition are they in?Is there an annual inspectionand maintenance plan?Is there an “action plan”to implement floodproofingmeasures when flooding ispredicted? Do the buildingoperators/occupants knowwhat to do when a floodwarning is issued?For existing buildings, whattypes of openings penetratethe building envelope belowthe 500-year flood elevationor the DFE (doors, windows,cracks, vent openings,plumbing fixtures, floordrains, etc.)?Are flood-resistant materialsused for structural andnonstructural componentsand finishes below the 500-year elevation or the DFE?Floodproofing measures are only as goodas the design and their condition, especiallyif many years have passed since initialinstallation. Floodproofing measures that requirehuman intervention are entirely dependent onthe adequacy of advance warning, and theavailability and ability of personnel to properlyinstall the measures.For dry floodproofing to be effective, everyopening must be identified and measures takento permanently seal or to prepare specialbarriers to resist infiltration. Sewage backflowcan enter through unprotected plumbingfixtures.Flood-resistant materials are capable ofwithstanding direct and prolonged contact withfloodwaters without sustaining damage thatrequires more than cosmetic repair. Contactis considered to be prolonged if it is 72 hoursor longer in freshwater flooding areas, or 12hours or longer in areas subject to coastalflooding.2-96 MAKING CRITICAL FACILITIES SAFE FROM Flooding

Table 2-3: Checklist for Building Vulnerability of Flood-Prone Critical Facilities (continued)Vulnerability Sections Guidance ObservationsUtility SystemsIs the potable water supplyfor the facility protectedfrom flooding? If servedby a well, is the wellheadprotected?Is the wastewater servicefor the building protectedfrom flooding? Are anymanholes below the DFE?Is infiltration of floodwatersinto sewer lines a problem?If the site is served by anonsite system that is locatedin a flood-prone area,have backflow valves beeninstalled?Are there any abovegroundor underground tanks onthe site in flood hazardareas? Are they installedand anchored to resistflotation during the designflood? Are tank openingsand vents elevated abovethe 500-year elevationor the DFE, or otherwiseprotected to prevent entryof floodwater or exit ofproduct during a floodevent?Operators of critical facilities that depend onfresh water for continued functionality shouldlearn about the vulnerability of the local watersupply system and the system’s plans forrecovery of service in the event of a flood.Most waste lines exit buildings at the lowestelevation. Even buildings that are outside of thefloodplain can be affected by sewage backupsduring floods.Dislodged tanks become floating debristhat pose special hazards during recovery.Lost product causes environmental damage.Functionality may be impaired if tanks forheating fuel, propane, or fuel for emergencygenerators are lost or damaged.Mechanical SystemsAre air handlers, HVACsystems, ductwork, andother mechanical equipmentand systems located abovethe 500-year elevation orthe DFE? Are the vents andinlets located above floodlevel, or sealed to prevententry of floodwater?In existing buildings, utility equipment that iscritical for functionality should be relocated tohigher floors or into elevated additions.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-97

Table 2-3: Checklist for Building Vulnerability of Flood-Prone Critical Facilities (continued)Vulnerability Sections Guidance ObservationsPlumbing and Gas SystemsAre plumbing fixtures andgas-fired equipment (meters,pilot light devices/burners,etc.) located above the 500-year elevation or the DFE?Is plumbing and gas pipingthat extends below floodlevels installed to minimizedamage?In existing buildings, utility equipment that iscritical for functionality should be relocated tohigher floors or into elevated additions.Piping that is exposed could be impacted bydebris.Electrical SystemsAre electrical systems,including backup powergenerators, panels, andprimary service equipment,located above the 500-yearelevation or the DFE?In existing buildings, utility equipment that iscritical for functionality should be relocated tohigher floors or into elevated additions.Are pieces of electricalstand-by equipment andgenerators equipped withcircuits to turn off power?Are the switches and wiringrequired for safety (minimallighting, door openers)located below the flood leveldesigned for use in damplocations?Fire Alarm SystemsIs the fire alarm systemlocated above the 500-yearelevation or the DFE?In existing buildings, utility equipment that iscritical for functionality should be relocated tohigher floors or into elevated additions.Communications and IT SystemsAre the communication/ITsystems located above the500-year elevation or theDFE?2-98 MAKING CRITICAL FACILITIES SAFE FROM Flooding

Table 2-3: Checklist for Building Vulnerability of Flood-Prone Critical Facilities (continued)StructuralVulnerability Sections Guidance ObservationsWhat is the constructiontype and the foundationtype and what is the loadbearing capacity?Has the foundationbeen designed toresist hydrostatic andhydrodynamic flood loads?If the building has belowgradeareas, are thelower floor slabs subject tocracking and uplift?If the building is elevatedon a crawlspace an openfoundation, are there anyenclosed areas?For an existing buildingwith high value uses belowthe flood elevation, isthe building suitable forelevation-in-place or canit be relocated to higherground?If siting in a floodplain is unavoidable, newfacilities are to be designed to account for allloads and load combinations, including floodloads.Building spaces below the design flood levelcan be dry floodproofed, although it must berecognized that higher flood levels will overtopthe protection measures and may result insevere damage. Dry floodproofing creates largeunbalanced forces that can jeopardize wallsand foundations that are not designed to resistthe hydrostatic and hydrodynamic loads.New buildings may have enclosures belowthe flood elevation provided the use of theenclosures is limited (crawlspace, parking,building access, limited storage). In addition,the enclosures must have flood openings toautomatically allow for inflow and outflow offloodwaters to minimize differential hydrostaticpressure.Existing buildings that are elevated and haveenclosures below the flood elevation can beretrofit with flood openings.Elevating a building provides better protectionthan dry floodproofing. Depending on the typeand soundness of the foundation, even largebuildings can be elevated on a new foundationor moved to a site outside of the floodplain.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-99

2.6 REFERENCES AND SOURCES OFADDITIONAL INFORMATIONAmerican Society of Civil Engineers, Structural Engineering Institute,Flood Resistant Design and Construction, ASCE/SEI 24-05,Reston, VA, 2005.American Society of Civil Engineers, Structural Engineering Institute,Minimum Design Loads for Buildings and Other Structures,ASCE/SEI 7-05, Reston, VA, 2005.Association of State Floodplain Managers, Inc., Floodplain Management2003: State and Local Programs, Madison, WI, 2004.FEMA, Answers to Questions about Substantially Damaged Buildings,FEMA 213, Washington, DC, May 1991.FEMA, Answers to Questions about the National Flood Insurance Program,FEMA 387, Washington, DC, August 2001.FEMA, Coastal Construction Manual, FEMA 55 (3rd Edition),Washington, DC, 2000.FEMA, Design and Construction Guidance for Community Shelters,FEMA 361, Washington, DC, July 2000.FEMA, Engineering Principles and Practices for Retrofitting Flood-proneResidential Buildings, FEMA 259, Washington, DC, January 1995.FEMA, Floodproofing Non-Residential Structures, FEMA 102, Washington,DC, May 1986.2-100 MAKING CRITICAL FACILITIES SAFE FROM Flooding

FEMA, Protecting Building Utilities From Flood Damage: Principles andPractices for the Design and Construction of Flood Resistant BuildingUtility Systems, FEMA 348, Washington, DC, November 1999.FEMA, NFIP Technical Bulletins:m User’s Guide to Technical Bulletins, FIA-TB-0, April 1993.m Openings in Foundation Walls, FIA-TB-1, April 1993.m Flood-Resistant Materials Requirements, FIA-TB-2, April 1993.m Non-Residential Floodproofing—Requirements and Certification,FIA-TB-3, April 1993.m Elevator Installation, FIA-TB-4, April 1993.m Free-of-Obstruction Requirements, FIA-TB-5, April 1993.m Below-Grade Parking Requirements, FIA-TB-6, April 1993.m Wet Floodproofing Requirements, FIA-TB-7, December 1993.m Corrosion Protection for Metal Connections in Coastal Areas, FIA-TB-8, 1996.m Design and Construction Guidance for Breakaway Walls BelowElevated Coastal Buildings, FIA-TB-9, 1999.m Ensuring That Structures Built on Fill In or Near Special FloodHazard Areas Are Reasonably Safe From Flooding, FIA-TB-10,2001.m Crawlspace Construction for Buildings Located in Special FloodHazard Areas, FIA-TB-11, 2001.International Code Council, Inc., ICC Performance Code for Buildingsand Facilities, Country Club Hills, IL, 2003.International Code Council, Inc., International Building Code,Country Club Hills, IL, 2003.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-101

International Code Council, Inc. and FEMA, Reducing Flood LossesThrough the International Codes, Meeting the Requirements of the NationalFlood Insurance Program (2nd Edition), Country Club Hills,IL, 2005.National Fire Protection Association, Building Construction andSafety Code (NFPA 5000), Quincy, MA, 2003.U.S. Army Corps of Engineers, Flood Proofing Regulations, EP 1165-2-314, Washington, DC, 1995.U.S. Army Corps of Engineers, National Flood Proofing Committee,Flood Proofing – How To Evaluate Your Options, Washington,DC, July 1993.U.S. Army Corps of Engineers, Flood Proofing Programs, Techniquesand References, Washington, DC, 1996.U.S. Army Corps of Engineers, Flood Proofing Performance—Successes& Failures, Washington, DC, 1998.Organizations and Agencies:FEMA: FEMA’s regional offices (www.fema.gov) can be contactedfor advice and guidance on NFIP mapping and regulations.NFIP State Coordinating offices help local governments to meettheir floodplain management obligations, and may provide technicaladvice to others; the offices are listed by the Association ofState Floodplain Managers, Inc. (www.floods.org/stcoor.htm).State departments of education or agencies that coordinate Statefunding and guidelines for critical facilities may have State-specificrequirements.U.S. Army Corps of Engineers: District offices offer Flood PlainManagement Services (www.usace.army.mil/inet/functions/cw/).FEMA publications may be obtained at no cost by calling (800)480-2520, faxing a request to (301) 497-6378, or downloaded fromthe library/publications section online at http://www.fema.gov.2-102 MAKING CRITICAL FACILITIES SAFE FROM Flooding

MAKING CRITICAL FACILITIES SAFE FROM High Wind 33.1 GENERAL DESIGNCONSIDERATIONSWind with sufficient speed to cause damage to weak criticalfacilities can occur anywhere in the United Statesand its territories. Even a well-designed, constructed,and maintained critical facility may be damaged in a wind eventmuch stronger than one the building was designed for. However,except for tornado damage, this scenario is a rare occurrence.Rather, most damage occurs because various building elementshave limited wind resistance due to inadequate design, poor installation,or material deterioration. Although the magnitude andfrequency of strong windstorms vary by locale, all critical facilitiesshould be designed, constructed, and maintained to minimizewind damage (other than that associated with tornadoes—seeSection 3.5).This chapter discusses structural, building envelope, andnonstructural building systems, and illustrates various types ofwind-induced damage that affect them. Numerous examples ofbest practices pertaining to new and existing critical facilities arepresented as recommended design guidelines. Incorporatingthose practices applicable to specific projects will result in greaterwind resistance reliability and will, therefore, decrease expendituresfor repair of wind-damaged facilities, provide enhancedprotection for occupants, and avoid disruption of critical services.1. The U.S. territories include American Samoa, Guam, Northern Mariana Islands, Puerto Rico, and the U.S. Virgin Islands. ASCE provides basicwind speed criteria for all but Northern Mariana Islands.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-1

3.1.1 Nature of High WindsA variety of windstorm types occur in different areas of the UnitedStates. The characteristics of the types of storms that can affect thesite should be considered by the design team. The primary stormtypes are listed below.Straight-line wind: This type of wind generally blows in a straightline and is the most common. Straight-line wind speeds rangefrom very low to very high. High winds associated with intenselow pressure can last for approximately a day at a given location.Straight-line winds occur throughout the United States and itsterritories.Down-slope wind: Wind blowing down the slope of mountains is referredto as down-slope wind. Down-slope winds with very highspeeds frequently occur in Alaska and Colorado. In the continentalUnited States, mountainous areasare referred to as “special wind regions”ASCE 7, Minimum Design Loads for(see Figure 3-1). Neither ASCE 7 nor modelBuildings and Other Structures, providesbuilding codes provide specific wind speedsguidance for determining wind loads onin special wind regions. ASCE 7 does providebuildings. The IBC and NFPA 5000 referguidance on how to determine design windto ASCE 7 for wind load determination.speeds in these regions. If the local buildingdepartment has not established the basicspeed, use of regional climatic data and consultationwith a wind engineer or meteorologist is advised.Thunderstorm: This type of storm can form rapidly and producehigh wind speeds. Approximately 10,000 severe thunderstormsoccur in the United States each year, typically in the spring andsummer. They are most common in the Southeast and Midwest.Besides producing high winds, they often create heavy rain andsometimes spawn tornadoes and hail storms. Thunderstorms commonlymove through an area quite rapidly, causing high winds foronly a few minutes at a given location. However, thunderstormscan also stall and become virtually stationary.Downburst: Also known as a microburst, this is a powerful downdraftassociated with a thunderstorm. When the downdraftreaches the ground, it spreads out horizontally, and may form oneor more horizontal vortex rings around the downdraft. The out-3-2 MAKING CRITICAL FACILITIES SAFE FROM High Wind

flow is typically 6,000 to 12,000 feet across, and the vortex ringmay rise 2,000 feet above the ground. The lifecycle of a downburstis usually 15 to 20 minutes. Observations suggest that approximately5 percent of all thunderstorms produce a downburst,which can result in significant damage in a localized area.Northeaster (nor’easter): A northeaster is a cyclonic storm occurringoff the east coast of North America. These winter weatherevents are notorious for producing heavy snow, rain, and highwaves and wind. A nor’easter gets its name from the continuouslystrong northeasterly winds blowing in from the ocean ahead ofthe storm and over the coastal areas. These storms may last for severaldays.Figure 3-1: Hurricane-prone regions and special wind regionsSOURCE: adapted from asce 7-05MAKING CRITICAL FACILITIES SAFE FROM High Wind3-3

The Saffir-Simpson Hurricane Scale is basedon measurements of sustained wind speedsin hurricanes; these measurements aretaken over open water. The wind speedsdescribed in the Saffir-Simpson HurricaneScale are used to prepare storm responseactions and are not intended to be usedfor building design. Design wind loads onbuildings should be determined using thebasic wind speeds given in ASCE 7.Hurricane: This is a system of spiraling winds converging withincreasing speed toward the storm’s center (the eye of the hurricane).Hurricanes form over warm ocean waters. The diameterof the storm varies and can be between 50 and 600 miles. A hurricane’sforward movement (translational speed) can vary betweenapproximately 5 miles per hour (mph) tomore than 25 mph. Besides being capableof delivering extremely strong winds for severalhours and moderately strong winds for aday or more, many hurricanes also bring veryheavy rainfall. Hurricanes also occasionallyspawn tornadoes. The Saffir-Simpson HurricaneScale (see Table 3-1) categorizes theintensity of hurricanes. The five-step scaleranges from Category 1 (the weakest) to Category5 (the strongest). Hurricane-proneregions are defined in Section 3.1.3.Of all the storm types, hurricanes have thegreatest potential for devastating a large geographical area and,hence, affect the greatest number of people. The terms “hurricane,”“cyclone,” and “typhoon” describe the same type of storm.The term used depends on the region of the world where thestorm occurs. See Figure 3-1 for hurricane-prone regions.Table 3-1: Saffir-Simpson Hurricane ScaleStrength Sustained Wind Speed (mph)* Gust Wind Speed (mph)** Pressure (millibar)Category 1 74-95 89-116 >980Category 2 96-110 117-134 965-979Category 3 111-130 135-159 945-964Category 4 131-155 160-189 920-944Category 5 >155 >189

Tornado: This is a violently rotating columnof air extending from the base of aThe majority of the tornadoes spawnedthunderstorm to the ground. The Fujitaduring hurricanes are classified as F2 orscale categorizes tornado severity based on weaker. However, a few F3 and at leastobserved damage. The six-step scale ranges two F4 tornadoes have been reported.from F0 (light damage) to F5 (incredibledamage). Weak tornadoes (F0 and F1) aremost common, but strong tornadoes (F2 and F3) frequently occur.Violent tornadoes (F4 and F5) are rare. Tornado path widths aretypically less than 1,000 feet; however, widths of approximately2.5 miles have been reported. Wind speed rapidly decreases withincreased distance from the center of a tornado. A critical facilityon the periphery of a strong or violent tornado could be subjectedto moderate to high wind speeds, depending upon the distancefrom the core of the tornado. However, eventhough the wind speed at a given facilitymight not be great, a facility on the peripherycould still be impacted by many largepieces of wind-borne debris. Tornadoes areresponsible for the greatest number of windrelateddeaths each year in the United States.Figure 3-2 shows the frequency of tornadooccurrence for a period between 1950 and1998, and Figure 3-3 shows the design windspeeds recommended by FEMA for designingcommunity shelters.Beginning in February 2007, the NationalWeather Service will use the EnhancedFujita Scale (EF-Scale) to categorizetornado severity. This new scale hassix steps, ranging from EF0 to EF5. Thenew scale was developed by Texas TechUniversity’s Wind Science and EngineeringCenter. See www.spc.noaa.gov/efscale/for further information on the EF-Scale.3.1.2 Probability of OccurrenceVia the importance factor, 2 ASCE 7 requires Category III and IVbuildings to be designed for higher wind loads than Category Iand II buildings (see Section 1.1.1). Hence, critical facilities designedin accordance with ASCE 7 have greater resistance tostronger, rarer storms. When designing a critical facility, designprofessionals should consider the following types of winds.Routine winds: In many locations, winds with low to moderatespeeds occur daily. Damage is not expected to occur duringthese events.2. The importance factor accounts for the degree of hazard to human life and damage to property. Importance factors are given in ASCE 7.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-5

Figure 3-2: Frequency of recorded F3, F4, and F5 tornadoes (1950-1998)Stronger winds: At a given site, stronger winds (i.e., winds with aspeed in the range of 70 to 80 mph peak gust, measured at 33feet in Exposure C --- refer to Section 3.1.3) may occur from severaltimes a year to only once a year or even less frequently. Thisis the threshold at which damage normally begins to occur tobuilding elements that have limited wind resistance due to problemsassociated with inadequate design, insufficient strength, poorinstallation, or material deterioration.Design level winds: Critical facilities exposed to design level eventsand events that are somewhat in excess of design level should experiencelittle, if any damage. Actual storm history, however,has shown that design level storms frequently cause extensivebuilding envelope damage. Structural damage also occurs, but less3-6 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Figure 3-3: Design wind speeds for community sheltersfrequently. Damage incurred in design level events is typically associatedwith inadequate design, poor installation, or materialdeterioration. The exceptions are wind-driven water infiltrationand wind-borne debris (missiles) damage. Water infiltration is discussedin Sections 3.3.3.1, 3.3.3.2, and 3.3.3.3.Tornadoes: Although more than 1,200 tornadoes typically occureach year in the United States, the probability of a tornado occurringat any given location is quite small. The probability ofoccurrence is a function of location. As shown in Figure 3-2, onlya few areas of the country frequently experience tornadoes, andtornadoes are very rare in the west. The Oklahoma City area is themost active location, with 112 recorded tornadoes between 1890and 2003 (www.spc.noaa.gov/faq/tornado/#History).MAKING CRITICAL FACILITIES SAFE FROM High Wind3-7

Missile damage is very common duringhurricanes and tornadoes. Missiles canpuncture roof coverings, many types ofexterior walls, and glazing. The IBC doesnot address missile-induced damageexcept for glazing in wind-borne debrisregions. (Wind-borne debris regions arelimited to portions of hurricane-proneregions.) In hurricane-prone regions,significant missile-induced buildingdamage should be expected, even duringdesign level hurricane events, unlessspecial enhancements are incorporatedinto the building’s design (discussed inSection 3.4).Well designed, constructed, and maintainedcritical facilities should experience little ifany damage from weak tornadoes, exceptfor window breakage. However, weak tornadoesoften cause building envelope damagebecause many critical facilities have wind resistancedeficiencies. Most critical facilitiesexperience significant damage if they are inthe path of a strong or violent tornado becausethey typically are not designed for thistype of storm.3.1.3 Wind/BuildingInteractionsWhen wind interacts with a building, bothpositive and negative (i.e., suction) pressuresoccur simultaneously (see Figure 3-4). Critical facilities musthave sufficient strength to resist the applied loads from thesepressures to prevent wind-induced building failure. Loads exertedon the building envelope are transferred to the structuralsystem, where in turn they must be transferred through thefoundation into the ground. The magnitude of the pressures isa function of the following primary factors.Figure 3-4:Schematic of wind-inducedpressures on a building3-8 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Exposure: The characteristics of the terrainFor additional exposure information,(i.e., ground roughness and surface irregularitiesin the vicinity of a building) influencesee the Commentary of ASCE 7, whichincludes several aerial photographs thatthe wind loading. ASCE 7 defines three exposurecategories, Exposures B, C, and D.illustrate the different terrain conditionsassociated with Exposures B, C, and D.Exposure B is the roughest terrain categoryand Exposure D is the smoothest. ExposureB includes urban, suburban, and woodedareas. Exposure C includes flat open terrain with scattered obstructionsand areas adjacent to water surfaces in hurricane-proneregions (which are defined below under “basic wind speed”).Exposure D includes areas adjacent to water surfaces outside hurricane-proneregions, mud flats, salt flats, and unbroken ice.Because of the wave conditions generated by hurricanes, areasadjacent to water surfaces in hurricane-prone regions are consideredto be Exposure C rather than the smoother Exposure D. Thesmoother the terrain, the greater the wind pressure; therefore,critical buildings located in Exposure C would receive higher windloads than those located in Exposure B, even at the same basicwind speed.Basic wind speed: ASCE 7 specifies the basic wind speed for determiningdesign wind loads. The basic wind speed is measured at 33feet above grade in Exposure C (flat open terrain). If the buildingis located in Exposure B or D, rather than C, an adjustment forthe actual exposure is made in the ASCE 7 calculation procedure.Since the 1995 edition of ASCE 7, the basic wind speed measurementhas been a 3-second peak gust speed. Prior to that time,the basic wind speed was a fastest-mile speed (i.e., the speed averagedover the time required for a mile-long column of air to passa fixed point). 3 Most of the United States has a basic wind speed(peak gust) of 90 mph, but much higher speeds occur in Alaskaand in hurricane-prone regions. The highest speed, 170 mph, occursin Guam.Hurricane-prone regions include Atlantic and Gulf coastal areas(where the basic wind speed is greater than 90 mph), Hawaii, and theU.S. territories in the Caribbean and South Pacific (see Figure 3-1).3. Peak gust speeds are about 15 to 20 mph higher than fastest-mile speeds (e.g., a 90-mph peak basic wind speed is equivalent to a 76-mphfastest-mile wind speed). IBC Chapter 16 provides a table of equivalent basic wind speeds.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-9

The MWFRS is an assemblage of structuralelements assigned to provide support andstability for the overall structure. The systemgenerally receives wind loading from morethan one surface. The C&C are elements ofthe building envelope that do not qualify aspart of the main wind-force resisting system.In the formula for determining wind pressures,the basic wind speed is squared.Therefore, as the wind speed increases, thepressures are exponentially increased, asillustrated in Figure 3-5. This figure also illustratesthe relative difference in pressuresexerted on the main wind-force resistingsystem (MWFRS) and the components andcladding (C&C) elements.Topography: Abrupt changes in topography, such as isolated hills,ridges, and escarpments, cause wind to speed up. Therefore, abuilding located near a ridge would receive higher wind pressuresthan a building located on relatively flat land. ASCE 7 provides aprocedure to account for topographic influences.Building height: Wind speed increases with height above theground. Taller buildings are exposed to higher wind speeds andgreater wind pressures. ASCE 7 provides a procedure to accountfor building height.Figure 3-5: Wind pressure as a function of wind speed3-10 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Internal pressure (building pressurization/depressurization): Openingsthrough the building envelope, in combination with wind interactingwith a building, can cause either an increase in thepressure within the building (i.e., positive internal pressure),or it can cause a decrease in the pressure (i.e., negative internalpressure). Building envelope openings occur around doors andwindow frames, and by air infiltration through walls that are notabsolutely airtight. A door or window left open, or glazing that isbroken during a storm, can greatly influence the magnitude ofthe internal pressure.Wind striking an exterior wall exerts a positive pressure on thewall, which forces air through openings and into the interior ofthe building (this is analogous to blowing up a balloon). At thesame time that the windward wall is receiving positive pressure,the side and rear walls are experiencing negative (suction) pressurefrom winds going around the building. As this occurs, airwithin the building is pulled out at openings in these walls. Asa result, if the porosity of the windward wall is greater than thecombined porosity of the side and rear walls, the interior of thebuilding is pressurized. But if the porosity of the windward wall islower than the combined porosity of the side and rear walls, theinterior of the building is depressurized (this is analogous to lettingair out of a balloon).When a building is pressurized, the internal pressure pushes upon the roof. This push from below the roof is combined with suctionon the roof above, resulting in an increased upward windpressure on the roof. The internal pressure also pushes on theside and rear walls. This outward push is combined with the suctionon the exterior side of these walls (see Figure 3-6). When abuilding becomes fully pressurized (e.g., due to window breakageor soffit failure), the loads applied to the exterior walls and roofare significantly increased. The rapid build-up of internal pressurecan also blow down interior partitions and blow suspendedceiling boards out of their support grid. The breaching of a smallwindow can be sufficient to cause full pressurization of the facility’sinterior.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-11

Figure 3-6:Schematic of internalpressure condition when thedominant opening is in thewindward wallWhen a building is depressurized, the internal pressure pulls theroof down, which reduces the amount of uplift exerted on theroof. The decreased internal pressure also pulls inward on thewindward wall, which increases the wind load on that wall (seeFigure 3-7).The ASCE 7 wind pressure design procedure accounts for the influenceof internal pressure on the wall and roof loads, and itprovides positive and negative internal pressure coefficients for3-12 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Figure 3-7:Schematic of internalpressure condition when thedominant opening is in theleeward walluse in load calculations. Buildings that are designed to accommodatefull pressurization are referred to as partially enclosedbuildings. Buildings that are only intended to experience limitedinternal pressurization are referred to as enclosed buildings.Buildings that do not experience internal pressurization are referredto as open buildings (such as covered walkways and mostparking garages).MAKING CRITICAL FACILITIES SAFE FROM High Wind3-13

Building shape: The highest uplift pressures occur at roof cornersbecause of building aerodynamics (i.e., the interactionbetween the wind and the building). The roof perimeter has asomewhat lower load compared to the corners, and the field ofthe roof has still lower loads. Exterior walls typically have lowerloads than the roof. The ends (edges) of walls have higher suctionloads than the portion of wall between the ends. However,when the wall is loaded with positive pressure, the entire wall isuniformly loaded. Figure 3-8 illustrates these aerodynamic influences.The negative values shown in Figure 3-8 indicate suctionpressure acting upward from the roof surface and outward fromthe wall surface. Positive values indicate positive pressure actinginward on the wall surface.Aerodynamic influences are accounted for by using external pressurecoefficients in load calculations. The value of the coefficientis a function of the location on the building (e.g., roof corner orfield of roof) and building shape as discussed below. Positive coefficientsrepresent a positive (inward-acting) pressure, and negativecoefficients represent negative (outward-acting [suction]) pressure.External pressure coefficients for MWFRS and C&C arelisted in ASCE 7.Building shape affects the value of pressure coefficients and,therefore, the loads applied to the various building surfaces. Forexample, the uplift loads on a low-slope roof are larger than theloads on a gable or hip roof. The steeper the slope, the lower theuplift load. Pressure coefficients for monoslope (shed) roofs, sawtoothroofs, and domes are all different from those for low-slopeand gable/hip roofs.Building irregularities, such as re-entrant corners, bay window projections,a stair tower projecting out from the main wall, dormers,and chimneys can cause localized turbulence. Turbulence causeswind speed-up, which increases the wind loads in the vicinity ofthe building irregularity, as shown in Figures 3-9 and 3-10. Figure3-9 shows the aggregate ballast on a hospital’s single-ply membraneroof blown away at the re-entrant corner and in the vicinityof the corners of the wall projections at the window bays. Theirregular wall surface created turbulence, which led to wind speedupand loss of aggregate in the turbulent flow areas.3-14 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Figure 3-8: Relative roof uplift pressures as a function of roof geometry, roof slope, and location on roof,and relative positive and negative wall pressures as a function of location along the wallMAKING CRITICAL FACILITIES SAFE FROM High Wind3-15

Figure 3-9:Aggregate blow-offassociated with buildingirregularities. HurricaneHugo (South Carolina,1989)Figure 3-10 shows a stair tower at a hospitalInformation pertaining to load calculationsthat caused turbulence resulting in windis presented in Section 3.3.1.2. For furtherspeed-up. The speed-up increased the suctionpressure on the base flashing along thegeneral information on the nature ofwind and wind-building interactions, seeparapet behind the stair tower. The builtuproof’s base flashing was pulled out fromBuildings at Risk: Wind Design Basics forPracticing Architects, American Institute ofunderneath the coping because its attachmentwas insufficient to resist the suctionArchitects, 1997.pressure. The base flashing failure propagatedand caused a large area of the roofmembrane to lift and peel. Some of the wall covering on thestair tower was also blown away. Had the stair tower not existed,the built-up roof would likely not have been damaged. To avoiddamage in the vicinity of building irregularities, attention needsto be given to the attachment of building elements located inturbulent flow areas.To avoid the roof membrane damage shown in Figure 3-10, itwould be prudent to use corner uplift loads in lieu of perimeteruplift loads in the vicinity of the stair tower, as illustrated inFigure 3-11. Wind load increases due to building irregularitiescan be identified by wind tunnel studies; however, wind tunnelstudies are rarely performed for critical facilities. Therefore,identification of wind load increases due to building irregu-3-16 MAKING CRITICAL FACILITIES SAFE FROM High Wind

larities will normally be based on the designer’s professionaljudgment. Usually load increases will only need to be applied tothe building envelope, and not to the MWFRS.Figure 3-10:The irregularity created bythe stair tower (coveredwith a metal roof) causedturbulence resulting inwind speed-up and roofdamage. HurricaneAndrew (Florida, 1992)Figure 3-11:Plan view of a portion ofthe building in Figure 3-10 showing the use of acorner uplift zone in lieuof a perimeter uplift zoneon the low-slope roof in thevicinity of the stair towerMAKING CRITICAL FACILITIES SAFE FROM High Wind3-17

3.1.4 Building CodesThe IBC is the most extensively used model code. However, insome jurisdictions NFPA 5000 may be used. In other jurisdictions,one of the earlier model building codes, or a specially writtenState or local building code, may be used. The specific scope and/or effectiveness and limitations of these other building codes willbe somewhat different than those of the IBC. It is incumbentupon the design professionals to be aware of the specific code (includingthe edition of the code and local amendments) that hasbeen adopted by the authority having jurisdiction over the locationof the critical facility.3.1.4.1 Scope of Building CodesWith respect to wind performance, the scope of the modelbuilding codes has greatly expanded since the mid-1980s. Some ofthe most significant improvements are discussed below.Recognition of increased uplift loads at the roof perimeter and corners:Prior to the 1982 edition of the Standard Building Code (SBC),Uniform Building Code (UBC), and the 1987 edition of the NationalBuilding Code (NBC), these model codes did not accountfor the increased uplift at the roof perimeter and corners. Therefore,critical facilities designed in accordance with earlier editionsof these codes are very susceptible to blow-off of the roof deckand/or roof covering.Adoption of ASCE 7 for design wind loads: Although the SBC, UBC,and NBC permitted use of ASCE 7, the 2000 edition of the IBCwas the first model code to require ASCE 7 for determiningwind design loads. ASCE 7 has been more reflective of the currentstate of the knowledge than the earlier model codes, anduse of this procedure typically has resulted in higher designloads.Roof coverings: Several performance and prescriptive requirementspertaining to wind resistance of roof coverings have beenincorporated into the model codes. The majority of these additionalprovisions were added after Hurricanes Hugo (1989) andAndrew (1992). Poor performance of roof coverings was wide-3-18 MAKING CRITICAL FACILITIES SAFE FROM High Wind

spread in both of those storms. Prior to the1991 edition of the SBC and UBC, and the1990 edition of the NBC, these model codeswere essentially silent on roof covering windloads and test methods for determininguplift resistance. Code improvements continuedto be made through the 2006 editionof the IBC, which added a provision thatprohibits aggregate roof surfaces in hurricane-proneregions.Glazing protection: The 2000 edition of theIBC was the first model code to addresswind-borne debris requirements for glazingin buildings located in hurricane-prone regions(via reference to the 1998 edition ofASCE 7). The 1995 edition of ASCE 7 wasthe first edition to address wind-borne debrisrequirements.ASCE 7 requires impact-resistant glazing inwind-borne debris regions within hurricaneproneregions. Impact-resistant glazing caneither be laminated glass, polycarbonate,or shutters tested in accordance withstandards specified in ASCE 7. Thewind-borne debris load criteria weredeveloped to minimize property damageand to improve building performance. Thecriteria were not developed for occupantprotection. Where occupant protection isa specific criterion, the more conservativewind-borne debris criteria given in FEMA361, Design and Construction Guidancefor Community Shelters is recommended.Parapets and rooftop equipment: The 2003 edition of the IBC wasthe first model code to address wind loads on parapets androoftop equipment (via reference to the 2002 edition of ASCE 7,which was the first edition of ASCE 7 to address these elements).3.1.4.2 Effectiveness and Limitations of BuildingCodesA key element of an effective building code is for a community tohave an effective building department. Building safety depends onmore than the codes and the standards they reference. Buildingsafety results when trained professionals have the resources andongoing support they need to stay on top of the latest advancementsin building safety. An effective building safety systemprovides uniform code interpretations, product evaluations, andprofessional development and certification for inspectors andplan reviewers. Local building departments play an important rolein helping to ensure buildings are designed and constructed inaccordance with the applicable building codes. Meaningful planreview and inspection by the building department are particularlyimportant for critical facilities.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-19

General limitations to building codes include the following:m Because codes are adopted and enforced on the local orState level, the authority having jurisdiction has the power toeliminate or modify wind-related provisions of a model code,or write its own code instead. In places where importantwind-related provisions of the current model code are notadopted and enforced, critical facilities are more susceptibleto wind damage. Additionally, a significant time lag often existsbetween the time a model code is updated and the timeit is implemented by the authority having jurisdiction. Buildingsdesigned to the minimum requirements of an outdatedcode are, therefore, not taking advantage of the currentstate of the knowledge. These buildings are prone to poorerwind performance compared to buildings designed accordingto the current model code.m Adopting the current model code alone does not ensure goodwind performance. The code is a minimum tool that shouldbe used by knowledgeable design professionals in conjunctionwith their training, skills, professional judgment, and the bestpractices presented in this manual. To achieve good windperformance, in addition to good design, the constructionwork must be effectively executed, and the building must beadequately maintained and repaired.m Critical facilities need to perform at a higher level thanrequired by codes and standards. See Section 1.3 onperformance based design.IBC 2006: The 2006 edition of the IBC is believed to be a relativelyeffective code, provided that it is properly followed andenforced. Some limitations of the 2006 IBC have, however, beenidentified:m With respect to hurricanes, the IBC provisions pertainingto building envelopes and rooftop equipment do notadequately address the special needs of critical facilities.For example: (1) they do not account for water infiltrationdue to puncture of the roof membrane by missiles; (2)they do not adequately address the vulnerabilities of brittleroof coverings (such as tile) to missile-induced damage3-20 MAKING CRITICAL FACILITIES SAFE FROM High Wind

and subsequent progressive failure;(3) they do not adequately addressoccupant protection with respect tomissiles; (4) they do not adequatelyaddress protection of equipment inelevator penthouses; (5) they do notaccount for interruption of water serviceor prolonged interruption of electricalpower; and (6) the current requirementsfor shelters are limited. All of theseelements are of extreme importance forcritical facilities, which need to remainoperational before, during, and after adisaster. Guidance to overcome theseshortcomings is given in Section 3.4.m The 2006 IBC does not account fortornadoes; therefore, except for weaktornadoes, it is ineffective for this typeof storm. 4 Guidance to overcome thisshortcoming is given in Section 3.5.The 2000, 2003, and 2006 IBC rely on severalreferenced standards and test methodsdeveloped or updated in the 1990s. Priorto adoption, most of these standards andtest methods had not been validated by actual building performanceduring design level wind events. The hurricanes of 2004and 2005 provided an opportunity to evaluate the actual performanceof buildings designed and constructed to the minimumprovisions of the IBC. Building performance evaluations conductedby FEMA revealed the need for further enhancements:m A limitation of the 2006 IBC pertains to some of the testmethods used to assess wind and wind-driven rain resistanceof building envelope components. However, before this codelimitation can be overcome, research needs to be conductedand new test methods need to be developed.The International Code Council (ICC)is developing a consensus standard,ICC/NSSA Standard for the Design andConstruction of Storm Shelters, to providebasic requirements for the design andconstruction of emergency shelters in areasaffected by hurricanes and tornadoes. Ifit is adopted by a community when itbecomes available in early 2007, it willprovide design and construction standardsfor buildings intended to resist the impactof high winds and wind-borne debris. Thisstand-alone standard will be linked to theIBC and IRC. It is the intent of the ICCthat the shelter standard be incorporatedby reference into the IBC and IRC in2009. FEMA should be consulted prior todesigning or constructing shelters to theICC/NSSA standard with FEMA fundsto ensure all program requirements aremet, as some components may need tobe designed to stricter criteria than thoseincluded in the consensus standard.4. Except for glass breakage, code-compliant buildings should not experience significant damage during weak tornadoes.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-21

m Except to the extent covered by reference to ASCE 7, the 2006IBC does not address the need for continuity, redundancy,or energy-dissipating capability (ductility) to limit the effectsof local collapse, and to prevent or minimize progressivecollapse after the loss of one or two primary structuralmembers, such as a column. Chapter 1 of ASCE 7 addressesgeneral structural integrity, and the Chapter 1 Commentaryprovides some guidance on this issue.3-22 MAKING CRITICAL FACILITIES SAFE FROM High Wind

3.2 CRITICAL FACILITIES EXPOSED TOHIGH WINDS3.2.1 Vulnerability: What High WindsCan Do to Critical FacilitiesThis section provides an overview of the common types of winddamage and their ramifications.3.2.1.1 Types of Building DamageWhen damaged by wind, critical facilities typically experiencea variety of building component damage. The most commontypes of damage are discussed below in descending order offrequency.Roof: Roof covering damage (including rooftop mechanical,electrical, and communications equipment) is the mostcommon type of wind damage. The school, illustrated in Figure3-12, was being used as a hurricane shelter at the time a portionof the roof membrane blew off. In addition to the membranedamage, several pieces of rooftop equipment were damaged,and virtually all of the loose aggregate blew off and broke manywindows in nearby houses. The cast-in-place concrete deck keptmost of the water from entering the building.Glazing: Exterior glazing damage is very common during hurricanesand tornadoes, but is less common during other storms.The glass shown in Figure 3-13 was broken by the aggregateMAKING CRITICAL FACILITIES SAFE FROM High Wind3-23

from a built-up roof. The inner panes had several impact craters.In several of the adjacent windows, both the outer andinner panes were broken. The aggregate flew more than 245feet (the estimated wind speed was 104 mph, measured at 33feet in Exposure C).Figure 3-12:A portion of the built-upmembrane lifted andpeeled after the metaledge flashing lifted.Hurricane Andrew(Florida, 1992)Figure 3-13:The outer window paneswere broken by aggregatefrom a built-up roof.Hurricane Hugo (SouthCarolina, 1989)3-24 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Wall coverings, soffits, and large doors: Exterior wall covering, soffit,and large door damage is common during hurricanes and tornadoes,but is less common during other storms. At the buildingshown in Figure 3-14, metal wall covering was attached to plywoodover metal studs. The CMU wall behind the studs did not appearto be damaged. The building was located on the periphery of a violenttornado.Wall collapse: Collapse of non-load-bearing exterior walls iscommon during hurricanes and tornadoes, but is less commonduring other storms (see Figure 3-15).Figure 3-14:Collapsed metal studwall—the wall wasblown completely awayin another part of thebuilding. (Oklahoma,1999)Figure 3-15:The unreinforced CMUwall collapsed at a schoolduring Hurricane Marilyn.(U.S. Virgin Islands, 1995)MAKING CRITICAL FACILITIES SAFE FROM High Wind3-25

Structural system: Structural damage (e.g., roof deck blow-off, blowoffor collapse of the roof structure, collapse of exterior bearingwalls, or collapse of the entire building or major portions thereof)is the principal type of damage that occurs during strong and violenttornadoes (see Figure 3-16).Figure 3-16:The school wing wasdestroyed by a violenttornado. (Oklahoma,1999)Modest wind speeds can drive rain intoexterior walls. Unless adequate provisionsare taken to account for water infiltration(see Sections 3.3.3.1 to 3.3.3.3),damaging corrosion, dry rot, and moldcan occur within walls.3.2.1.2 Ramifications of DamageThe ramifications of building component damage on critical facilitiesare described below.Property damage: Property damage requires repairing/replacingthe damaged components (or replacing the entire facility), andmay require repairing/replacing interior building components,furniture, and other equipment, and mold remediation. Evenwhen damage to the building envelope islimited, such as blow-off of a portion of theroof covering or broken glazing, substantialwater damage frequently occurs becauseheavy rains often accompany strong winds(particularly in the case of thunderstorms,tropical storms, hurricanes, and tornadoes).At the newly constructed gymnasiumshown in Figure 3-17, the structural metal3-26 MAKING CRITICAL FACILITIES SAFE FROM High Wind

oof panels were applied over metal purlins. The panels with 3-inch-high trapezoidal ribs at 24 inches on center detached fromtheir concealed clips. A massive quantity of water entered thebuilding and buckled the wood floor.Figure 3-17:A massive quantity ofwater entered the buildingafter the roof blew off.Typhoon Paka (Guam,1997)Wind-borne debris such as roof aggregate, gutters, rooftopequipment, and siding blown from buildings can damage vehiclesand other buildings in the vicinity. Debris can travel wellover 300 feet in high-wind events.Portable classrooms on school campuses are often particularlyvulnerable to significant damage because they are seldom designedto the same wind pressures as permanent buildings.Portable classrooms are frequently blown over during high-windevents, because the anchoring techniques typically used are inadequateto secure the units to the ground. Wind-borne debrisfrom portable classrooms, or an entire portable classroom, maystrike the permanent school building and cause serious damage.Ancillary buildings (such as storage buildings) adjacent to criticalfacilities are also vulnerable to damage. Although loss ofthese buildings may not be detrimental to the operation of thecritical facility, debris from ancillary buildings may strike anddamage the critical facility. The damaged building shown inMAKING CRITICAL FACILITIES SAFE FROM High Wind3-27

Figure 3-18 contained the hospital’s supplies and maintenanceshop. With the loss of this building, tents had to be set up to providesupply storage. Almost all of the tools and stock materials forrepairs were lost.Figure 3-18:A hurricane-damaged,pre-engineered storagebuilding adjacent toa hospital. HurricaneCharley (Florida, 2004)Although people are not usually outsideduring hurricanes, it is not uncommon forpeople to seek shelter or assistance incritical facilities during a storm. Missiles,such as roof aggregate or tile sheddingfrom a critical facility, could injure or killlate arrivals before they have a chance toenter the building.Injury or death: Although infrequent, criticalfacility occupants or people outside thefacility have been injured and killed whenstruck by collapsed building components(such as exterior masonry walls or the roofstructure) or wind-borne debris. The greatestrisk of injury or death is during strong hurricanesand strong/violent tornadoes.Interrupted use: Depending on the magnitudeof wind and water damage, it cantake days, months, or more than a year to repair the damageor replace a facility. In addition to the costs associated with repairing/replacingthe damage, other social and financial costscan be even more significant. The repercussions related to interrupteduse of the critical facility can include the loss of emergencyand first-responder services, lack of medical care, and the coststo rent temporary facilities. These additional costs can be quitesubstantial.3-28 MAKING CRITICAL FACILITIES SAFE FROM High Wind

3.2.2 Evaluating Critical Facilities forRisk from High WindsThis section describes the process of hazard risk assessment. Althoughno formal methodology for risk assessment has beenadopted, prior experience provides a sufficient knowledge baseupon which a set of guidelines can be structured into a recommendedprocedure for risk assessment of critical facilities. Theprocedures presented below establish guidelines for evaluatingthe risk to new and existing buildings from wind storms otherthan tornadoes. These evaluations will allow development of avulnerability assessment that can be used along with the site’swind regime to assess the risk to critical facilities.In the case of tornadoes, neither the IBC nor ASCE 7 requiresbuildings (including critical facilities) to be designed to resisttornado forces, nor are occupant shelters required in buildingslocated in tornado-prone regions. Constructing tornado-resistantcritical facilities is extremely expensive because of theextremely high pressures and missile impact loads that tornadoescan generate. Therefore, when consideration is voluntarilygiven to tornado design, the emphasis istypically on occupant protection, which isachieved by “hardening” portions of a criticalfacility for use as safe havens. FEMA 361includes a comprehensive risk assessmentprocedure that designers can use to assistbuilding owners in determining whether atornado shelter should be included as partof a new critical facility. See Section 3.5 forthe design of tornado shelters and otherrecommendations pertaining to critical facilitiesin tornado-prone regions.3.2.2.1 New BuildingsWhen designing new critical facilities, atwo-step procedure is recommended forevaluating the risk from wind storms (otherthan tornadoes).In this manual, the term “tornado-proneregions” refers to those areas of the UnitedStates where the number of recordedF3, F4, and F5 tornadoes per 3,700square miles is 6 or greater per year(see Figure 3-2). However, an owner ofa critical facility may decide to use otherfrequency values (e.g., 1 or greater, 16or greater, or greater than 25) in definingwhether the building is in a tornado-pronearea. In this manual, tornado shelters arerecommended for all critical facilities intornado-prone regions.Where the frequency value is 1 or greater,and the facility does not have a tornadoshelter, the best available refuge areasshould be identified, as discussed inSection 3.5.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-29

Step 1: Determine the basic wind speed from ASCE 7. As thebasic wind speed increases beyond 90 mph, the risk of damage increases.Design, construction, and maintenance enhancementsare recommended to compensate for the increased risk of damage(see Section 3.3).Step 2: For critical facilities in hurricane-prone regions, refer tothe design, construction, and maintenance enhancements recommendedin Section 3.4.For particularly important critical facilities (such as hospitals)in remote areas outside of hurricane-prone regions, it is recommendedthat robust design measures be considered to minimizethe potential for disruption resulting from wind damage. Becauseof their remote location, disruption of such facilities couldseverely affect the occupants or community. Some of the recommendationsin Section 3.4 may therefore be prudent.3.2.2.2 Existing BuildingsThe resistance of existing buildings is a function of their originaldesign and construction, various additions or modifications, andthe condition of building components (which may have weakeneddue to deterioration or fatigue). For existing buildings, a two-stepprocedure is also recommended.Step 1: Calculate the wind loads on the building using the currentedition of ASCE 7, and compare these loads with theloads for which the building was originally designed. The originaldesign loads may be noted on the contract drawings. Ifnot, determine what building code or standard was used to developthe original design loads, and calculate the loads usingthat code or standard. If the original design loads are significantlylower than current loads, upgrading the load resistanceof the building envelope and/or structure should be considered.An alternative to comparing current loads with originaldesign loads is to evaluate the resistance of the existing facilityas a function of the current loads to determine what elementsare highly overstressed.3-30 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Step 2: Perform a field investigation to evaluate the primarybuilding envelope elements, rooftop equipment, and structuralsystem elements, to determine if the facility was generallyconstructed as indicated on the original contract drawings.As part of the investigation, the primary elements should bechecked for deterioration. Load path continuity should also bechecked.If the results of either step indicate the need for remedial work,see Section 3.6.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-31

3.3 CRITICAL FACILITY DESIGNCONSIDERATIONS3.3.1 General Design ConsiderationsThe performance of critical facilities in past wind storms indicatesthat the most frequent and the most significant factor inthe disruption of the operations of these facilities has been thefailure of nonstructural building components. While acknowledgingthe importance of the structural systems, Chapter 3 emphasizesthe building envelope components and the nonstructural systems.According to the National Institute of Building Science (NIBS),the building envelope includes the below-grade basement wallsand foundation and floor slab (although these are generally consideredpart of the building’s structural system). The envelope includeseverything that separates the interior of a building from the outdoorenvironment, including the connection of all the nonstructuralelements to the building structure. The nonstructural systems includeall mechanical, electrical, electronic, communications, andlightning protection systems. Historically, damage to roof coveringsand rooftop equipment has been the leading cause ofbuilding performance problems during wind storms. Special considerationshould be given to the problem of water infiltrationthrough failed building envelope components, which can causesevere disruptions in the functioning of critical facilities.The key to enhanced wind performance is paying sufficient attentionto all phases of the construction process (including siteselection, design, and construction) and to post-occupancy maintenanceand repair.3-32 MAKING CRITICAL FACILITIES SAFE FROM High Wind

3.3.1.1 SiteWhen selecting land for a critical facility, sites located in ExposureD (see Section 3.1.3 for exposure definitions) should be avoided ifpossible. Selecting a site in Exposure C or preferably in ExposureB would decrease the wind loads. Also, where possible, avoid selectingsites located on an escarpment or the upper half of a hill,where the abrupt change in the topography would result in increasedwind loads. 6Trees with trunks larger than 6 inches in diameter, poles (e.g.,light fixture poles, flag poles, and power poles), or towers (e.g.,electrical transmission and large communication towers) shouldnot be placed near the building. Falling trees, poles, and towerscan severely damage a critical facility and injure the occupants(see Figure 3-19). Large trees can crash through pre-engineeredmetal buildings (which often house fire stations) andwood frame construction (which is commonly used for nursinghomes). Falling trees can also rupture roof membranes andbreak windows.Figure 3-19:Had this tree fallen inthe opposite direction, itwould have landed onthe school. Hurricane Ivan(Florida, 2004)6. When selecting a site on an escarpment or the upper half of a hill is necessary, the ASCE 7 design procedure accounts for wind speed-upassociated with this abrupt change in topography.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-33

In the past, design professionals seldomperformed load calculations on thebuilding envelope (i.e., roof and wallcoverings, doors, windows, and skylights)and rooftop equipment. These buildingcomponents are the ones that have failedthe most during past wind events. Inlarge part they failed because of thelack of proper load determination andinappropriate design of these elements.It is imperative that design professionalsdetermine the loads for the buildingenvelope and rooftop equipment, anddesign them to accommodate such loads.Providing at least two means of site egress isprudent for all critical facilities, but is particularlyimportant for facilities in hurricane-proneregions. If one route becomes blocked by treesor other debris, or by floodwaters, the other accessroute may still be available.3.3.1.2 Building DesignGood wind performance depends on gooddesign (including details and specifications),materials, installation, maintenance,and repair. A significant shortcoming inany of these five elements could jeopardizethe performance of a critical facility againstwind. Design, however, is the key element toachieving good performance of a building against wind damage.Design inadequacies frequently cannot be compensated for withother elements. Good design, however, can compensate for otherinadequacies to some extent. The following steps should be includedin the design process for critical facilities.Step 1: Calculate LoadsUplift loads on roof assemblies can alsobe determined from FM Global (FMG)Data Sheets. If the critical facility is FMGinsured, and the FMG-derived loads arehigher than those derived from ASCE 7 orthe building code, the FMG loads shouldgovern. However, if the ASCE 7 or codederivedloads are higher than those fromFMG, the ASCE 7 or code-derived loadsshould govern (whichever procedureresults in the highest loads).Calculate loads on the MWFRS, the building envelope, androoftop equipment in accordance with ASCE 7 or the localbuilding code, whichever procedure results in the highest loads.In calculating wind loads, design professionalsshould consider the following items.Importance factor: The effect of using a 1.15importance factor versus 1 is that the designloads for the MWFRS and C&C are increasedby 15 percent. The importance factor formost critical facilities is required to be 1.15.However, ASCE 7 permits a factor of 1 forsome critical facilities. For example, schoolswith an occupant load of less than 250people are permitted to be designed with animportance factor of only 1 (provided theyare not used as a shelter—if used as a shelter,3-34 MAKING CRITICAL FACILITIES SAFE FROM High Wind

schools are required to be designed with an importance factor of1.15, regardless of occupant load). Other facilities where occupantload controls the importance factor include certain healthcare facilities, such as nursing homes with 50 or more residents,for which a factor of 1.15 is required. For nursing homes with lessthan 50 residents, a factor of 1 can be used. Some critical facilitiesare not specifically addressed in ASCE 7. For example, variousbuildings on a hospital campus, such as medical office buildingsthat are integrally connected to the hospital and various types ofnon-emergency treatment facilities (such as storage, cancer treatment,physical therapy, and dialysis) are not specifically requiredby ASCE 7 to be designed with a 1.15 factor. This manual recommendsa value of 1.15 for all critical facilities.Wind directionality factor: The ASCE 7 wind load calculation procedureincorporates a wind directionality factor (k d). Thedirectionality factor accounts for the reduced probability of maximumwinds coming from any given direction. By applying theprescribed value of 0.85, the loads are reduced by 15 percent. Becausehurricane winds can come from any direction, and becauseof the historically poor performance of building envelopes androoftop equipment, this manual recommends a more conservativeapproach for critical facilities in hurricane-prone regions. A directionalityfactor of 1.0 is recommended for the building envelopeand rooftop equipment (a load increase over what is required byASCE 7). For the MWFRS, a directionality factor of 0.85 is recommended(hence, no change for MWFRS).Step 2: Determine Load ResistanceWhen using allowable stress design, after loads have been determined,it is necessary to select a reasonable safety factor inorder to determine the minimum required load resistance.For building envelope systems, a minimum safety factor of 2 isrecommended. For anchoring exterior-mounted mechanical,electrical, and communications equipment (such as satellitedishes), a minimum safety factor of 3 is recommended. Whenusing strength design, load combinations and load factors specifiedin ASCE 7 are used.ASCE 7 provides criteria for combining wind loads with other typesof loads (such as dead and flood loads) using allowable stress design.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-35

When using allowable stress design, asafety factor is applied to account forreasonable variations in material strengths,construction workmanship, and conditionswhen the actual wind speed somewhatexceeds the design wind speed. Fordesign purposes, the ultimate resistancean assembly achieves in testing is reducedby the safety factor. For example, if aroof assembly resisted an uplift pressureof 100 pounds per square foot (psf), afterapplying a safety factor of 2, the assemblywould be suitable where the design loadwas 50 psf or less. Conversely, if thedesign load is known, multiplying it by thesafety factor equals the minimum requiredtest pressure (e.g., 50 psf design loadmultiplied by a safety factor of 2 equals aminimum required test pressure of 100 psf).For structural members and cladding elementswhere strength design can be used,load resistance can be determined by calculations.For other elements where allowablestress design is used (such as most types ofroof coverings), load resistance is primarilyobtained from system testing.The load resistance criteria need to be providedin contract documents. For structuralelements, the designer of record typically accountsfor load resistance by indicating thematerial, size, spacing, and connection of theelements. For nonstructural elements, suchas roof coverings or windows, the load andsafety factor can be specified. In this case, thespecifications should require the contractor’ssubmittals to demonstrate that the system willmeet the load resistance criteria. This performancespecification approach is necessary if,at the time of the design, it is unknown whowill manufacture the system.Connections are a key aspect of loadpath continuity between various structuraland nonstructural building elements. In awindow, for example, the glass must bestrong enough to resist the wind pressureand must be adequately anchored to thewindow frame, the frame adequatelyanchored to the wall, the wall to thefoundation, and the foundation to theground. As loads increase, greaterload capacity must be developed in theconnections.Regardless of which approach is used, it is important that thedesigner of record ensure that it can be demonstrated, via calculationsor tests, that the structure, building envelope, andnonstructural systems (exterior-mounted mechanical, electrical,and communications equipment) have sufficientstrength to resist design wind loads.Step 3: Detailed DesignIt is vital to design, detail, and specify thestructural system, building envelope, andexterior-mounted mechanical, electrical,and communications equipment to meetthe factored design loads (based on appropriateanalytical or test methods). Itis also vital to respond to the risk assessmentcriteria discussed in Section 3.2.2, asappropriate.3-36 MAKING CRITICAL FACILITIES SAFE FROM High Wind

As part of the detailed design effort, load path continuityshould be clearly indicated in the contract documents via illustrationof connection details. Load paths need to accommodatedesign uplift, racking, and overturning loads. Load path continuityobviously applies to MWFRS elements, but it also appliesto building envelope elements. Figure 3-20 shows a load pathdiscontinuity between a piece of HVAC equipment and itsequipment stand. The equipment on this new Federal courthouseblew away because it was resting on vibration isolatorsthat provided lateral resistance, but no uplift resistance (also seeFigure 3-75).Figure 3-20:Temporary coveringsplaced over two largeopenings in the roof thatwere left after the ductworkblew away. HurricaneKatrina (Mississippi, 2005)Figure 3-21 illustrates the load path concept. Members are sizedto accommodate the design loads. Connections are designed totransfer uplift loads applied to the roof, and the positive and negativeloads applied to the exterior bearing walls, down to thefoundation and into the ground. The roof covering (and wallcovering, if there is one) is also part of the load path. To avoidblow-off, the nonstructural elements must also be adequately attachedto the structure.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-37

Figure 3-21:Illustration of load pathcontinuityAs part of the detailed design process, special considerationshould be given to the durability of materials and waterinfiltration.Durability: Because some locales have very aggressive atmosphericcorrosion (such as areas near oceans), special attention needsto be given to the specification of adequate protection for ferrousmetals, or to specify alternative metals such as stainless3-38 MAKING CRITICAL FACILITIES SAFE FROM High Wind

steel. FEMA Technical Bulletin, CorrosionProtection for Metal Connectors in Coastal Areas(FIA-TB-8, 1996) contains information oncorrosion protection. Attention also needsto be given to dry rot avoidance, for example,by specifying preservative-treatedwood or developing details that avoid excessivemoisture accumulation. Appendix Jof the Coastal Construction Manual, (FEMA55, 2000) presents information on wooddurability.Coastal environments are conducive tometal corrosion, especially in buildingswithin 3,000 feet of the ocean. Mostjurisdictions require metal buildinghardware to be hot-dipped galvanizedor stainless steel. Some local codesrequire protective coatings that are thickerthan typical “off-the-shelf” products. Forexample, a G90 zinc coating (0.75 milon each face) may be required. Otherrecommendations include the following:Durable materials are particularly importantfor components that are inaccessibleand cannot be inspected regularly (such asfasteners used to attach roof insulation).Special attention also needs to be given todetails. For example, details that do notallow water to stand at connections or sillsare preferred. Without special attention tomaterial selection and details, the demandson maintenance and repair will be increased,along with the likelihood of failureof components during high winds.Water infiltration (rain): Although preventionof building collapse and major buildingdamage is the primary goal of wind-resistantdesign, consideration should also begiven to minimizing water damage and subsequentdevelopment of mold from thepenetration of wind-driven rain. To the extentpossible, non-load-bearing walls anddoor and window frames should be designedin accordance with rain-screenprinciples. With this approach, it is assumedthat some water will penetrate past the faceof the building envelope. The water is interceptedin an air-pressure equalized cavitythat provides drainage from the cavity to the outer surface ofthe building. See Sections 3.3.3.2 and 3.3.3.3, and Figure 3-40for further discussion and an example.m Use hot-dipped galvanized or stainlesssteel hardware. Reinforcing steel shouldbe fully protected from corrosion by thesurrounding material (masonry, mortar,grout, or concrete). Use galvanizedor epoxy-coated reinforcing steelin situations where the potential forcorrosion is high.m Avoid joining dissimilar metals,especially those with high galvanicpotential.m Avoid using certain wood preservativesin direct contact with galvanized metal.Verify that wood treatment is suitablefor use with galvanized metal, or usestainless steel.m Metal-plate-connected trusses shouldnot be exposed to the elements. Trussjoints near vent openings are moresusceptible to corrosion and mayrequire increased corrosion protection.Note: Although more resistant than othermetals, stainless steel is still subject tocorrosion.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-39

In conjunction with the rain-screen principle,it is desirable to avoid using sealantFurther information on the rain-screenprinciple can be found in the Nationalas the first or only line of defense againstInstitute of Building Sciences’ Buildingwater infiltration. When sealant joints areEnvelope Design Guide (www.wbdg.org/exposed, obtaining long-lasting watertightdesign/envelope.php).performance is difficult because of thecomplexities of sealant joint design and installation(see Figure 3-40, which shows the sealant protected by aremovable stop).Step 4: Peer ReviewIf the design team’s wind expertise and experience is limited,wind design input and/or peer review should be sought from aqualified individual. The design input or peer review could be arrangedfor the entire building, or for specific components such asthe roof or glazing systems, that are critical and beyond the designteam’s expertise.Regardless of the design team’s expertise and experience, peer reviewshould be considered when a critical facility:m Is located in an area where the basic wind speed is greaterthan 90 mph (peak gust)—particularly if the facility is ahospital, or will be used as an EOC or hurricane shelter.m Will incorporate a tornado shelter.3.3.1.3 Construction Contract AdministrationAfter a suitable design is complete, the design team should endeavorto ensure that the design intent is achieved duringconstruction. The key elements of construction contract administrationare submittal reviews and field observations, asdiscussed below.Submittal reviews: The specifications need to stipulate the submittalrequirements. This includes specifying what systems requiresubmittals (e.g., windows) and test data (where appropriate). Eachsubmittal should demonstrate the development of a load paththrough the system and into its supporting element. For example,3-40 MAKING CRITICAL FACILITIES SAFE FROM High Wind

a window submittal should show that the glazing has sufficientstrength, its attachment to the frame is adequate, and the attachmentof the frame to the wall is adequate.During submittal review, it is important for the designer of recordto be diligent in ensuring that all required documents aresubmitted and that they include the necessary information. Thesubmittal information needs to be thoroughly checked to ensureits validity. For example, if an approved method used todemonstrate compliance with the design load has been alteredor incorrectly applied, the test data should be rejected, unlessthe contractor can demonstrate the test method was suitable.Similarly, if a new test method has been developed by a manufactureror the contractor, the contractor should demonstrateits suitability.Field observations: It is recommended that the design team analyzethe design to determine which elements are critical to ensuringhigh-wind performance. The analysis should include the structuralsystem and exterior-mounted electrical equipment, but itshould focus on the building envelope and exterior-mountedmechanical and communications equipment. After determiningthe list of critical elements to be observed, observation frequencyand the need for special inspections by an inspection firmshould be determined. Observation frequency and the need forspecial inspections will depend on the results of the risk assessmentdescribed in Section 3.2.2, complexity of the facility, andthe competency of the general contractor, subcontractors, andsuppliers.See Section 3.4 for additional information pertaining to critical facilitieslocated in hurricane-prone regions.3.3.1.4 Post-Occupancy Inspections, PeriodicMaintenance, Repair, and ReplacementThe design team should advise the building owner of the importanceof periodic inspections, maintenance, and timely repair. Itis important for the building owner to understand that a facility’swind resistance will degrade over time due to exposure to weatherunless it is regularly maintained and repaired. The goal shouldMAKING CRITICAL FACILITIES SAFE FROM High Wind3-41

e to repair or replace items before they fail in a storm. Thisapproach is less expensive than waiting for failure and then repairingthe failed components and consequential damage.The building envelope and exterior-mounted equipment shouldbe inspected once a year by persons knowledgeable of thesystems/materials they are inspecting. Items that require maintenance,repair, or replacement should be documented andscheduled for work. For example, the deterioration of glazing isoften overlooked. After several years of exposure, scratches andchips can become extensive enough to weaken the glazing. Also, ifan engineered film was surface-applied to glazing for wind-bornedebris protection, the film should be periodically inspected andreplaced before it is no longer effective.A special inspection is recommended following unusually highwinds. The purpose of the inspection is to assess whether thestrong storm caused damage that needs to be repaired to maintainbuilding strength and integrity. In addition to inspectingfor obvious signs of damage, the inspector should determine ifcracks or other openings have developed that may allow water infiltration,which could lead to corrosion or dry rot of concealedcomponents.See Section 3.4 for additional information pertaining to buildingslocated in hurricane-prone regions.3.3.2 Structural SystemsBased on post-storm damage evaluations, with the exception ofstrong and violent tornado events, the structural systems (i.e.,MWFRS and structural components such as roof decking) of criticalfacilities have typically performed quite well during designwind events. There have, however, been notable exceptions; inthese cases, the most common problem has been blow-off of theroof deck, but instances of collapse have also been documented(see Figure 3-22). The structural problems have primarily beencaused by lack of an adequate load path, with connection failurebeing a common occurrence. Problems have also been caused byreduced structural capacity due to termites, workmanship errors(commonly associated with steel decks attached by puddle welds),3-42 MAKING CRITICAL FACILITIES SAFE FROM High Wind

and limited uplift resistance of deck connections in roof perimetersand corners (due to lack of code-required enhancement inolder editions of the model codes).Figure 3-22:Collapse of a large portionof a new pre-engineeredmetal building used as ashelter for approximately1,400 people. HurricaneCharley (Florida, 2004)With the exception of strong and violent tornado events, structuralsystems designed and constructed in accordance with theIBC should typically offer adequate wind resistance, provided attentionwas given to load path continuity and to the durabilityof building materials (with respect to corrosion and termites).However, the greatest reliability is offered by cast-in-place concrete.There are no known reports of any cast-in-place concretebuildings experiencing a significant structural problem duringwind events, including the strongest hurricanes (Category 5)and tornadoes (F5).MAKING CRITICAL FACILITIES SAFE FROM High Wind3-43

The following design parameters are recommended for structuralsystems (see Section 3.4.2 for critical facilities located in hurricane-proneregions):m If a pre-engineered metal building is being contemplated,special steps should be taken to ensure the structure has moreredundancy than is typically the case with pre-engineered buildings.7 Steps should be taken to ensure the structure is not vulnerableto progressive collapse in the event a primary bent (steelmoment frame) is compromised or bracing components fail.m Exterior load-bearing walls of masonry or precast concreteshould be designed to have sufficient strength to resist externaland internal loading when analyzed as C&C. CMU walls shouldhave vertical and horizontal reinforcing and grout to resist windloads. The connections of precast concrete wall panels shouldbe designed to have sufficient strength to resist wind loads.m For roof decks, concrete, steel, plywood, or oriented strandboard (OSB) is recommended.m For steel roof decks, it is recommended that a screwattachment be specified, rather than puddle welds orpowder-driven pins. Screws are more reliable and much lesssusceptible to workmanship problems. Figure 3-23 showsdecking that was attached with puddle welds. At most of thewelds, there was only superficial bonding of the metal deck tothe joist, as illustrated by this example. Only a small portion ofthe deck near the center of the weld area (as delineated by thecircle) was well fused to the joist. Figures 3-24 and 3-25 showproblems with acoustical decking attached with powder-drivenpins. The pin shown on the left of Figure 3-25 is properlyseated. However, the pin at the right did not penetrate farenough into the steel joist below.m For attaching wood sheathed roof decks, screws, ring-shank,or screw-shank nails are recommended in the corner regionsof the roof. Where the basic wind speed is greater than 90mph, these types of fasteners are also recommended for theperimeter regions of the roof.7. The structural system of pre-engineered metal buildings is composed of rigid steel frames, secondary members (including roof purlins and wallgirts made of Z- or C-shaped members) and bracing.3-44 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Figure 3-23:View looking down at thetop of a steel joist after themetal decking blew away.Only a small portion ofthe deck was well fusedto the joist (circled area).Tornado (Oklahoma,1999)Figure 3-24:Looking down at a sidelap of a deck attachedwith powder-driven pins. The washer at the top pinblew through the deck.Figure 3-25:View looking along a sidelap of a deck attachedwith powder-driven pins. The right pin does notprovide adequate uplift and shear resistance.m For precast concrete decks it is recommended that the deckconnections be designed to resist the design uplift loadsbecause the deck dead load itself is often insufficient to resistthe uplift. The deck in Figure 3-26 had bolts to provide upliftresistance; however, anchor plates and nuts had not beeninstalled. Without the anchor plates, the dead load of the deckwas insufficient to resist the wind uplift load.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-45

Figure 3-26:Portions of this waffledprecast concrete roof deckwere blown off. TyphoonPaka (Guam, 1997)m For precast Tee decks, it is recommended that the reinforcingbe designed to accommodate the uplift loads in additionto the gravity loads. Otherwise, large uplift forces can causemember failure due to the Tee’s own pre-stress forces afterthe uplift load exceeds the dead load of the Tee. This typeof failure occurred at one of the roof panels shown in Figure3-27, where a panel lifted because of the combined effects ofwind uplift and pre-tension. Also, because the connectionsbetween the roof and wall panels provided very little upliftload resistance, several other roof and wall panels collapsed.Figure 3-27:Twin-Tee roof panel liftedas a result of the combinedeffects of wind uplift andpre-tension. Tornado(Missouri, May 2003)3-46 MAKING CRITICAL FACILITIES SAFE FROM High Wind

m For buildings that have mechanically attached single-ply ormodified bitumen membranes, designers should refer tothe decking recommendations presented in the Wind DesignGuide for Mechanically Attached Flexible Membrane Roofs, B1049(National Research Council of Canada, 2005).m If an FMG-rated roof assembly is specified, the roof deck alsoneeds to comply with the FMG criteria.m Walkway and entrance canopies are often damaged duringhigh winds (see Figure 3-28). Wind-borne debris fromdamaged canopies can damage nearby buildings and injurepeople, hence these elements should also receive design andconstruction attention.Figure 3-28:The destroyed walkwaycanopy in front of a schoolbecame wind-bornedebris. Hurricane Ivan(Florida, 2004)ASCE 7-05 provides pressure coefficients for open canopies of various slopes (referred to as“free roofs” in ASCE 7). The free roof figures for MWFRS in ASCE 7-05 (Figures 6-18A to 6-18D)include two load cases, Case A and Case B. While there is no discussion describing the twoload cases, they pertain to fluctuating loads and are intended to represent upper and lowerlimits of instantaneous wind pressures. Loads for both cases must be calculated to determine thecritical loads. Figures 6-18A to 6-18C are for a wind direction normal to the ridge. For winddirection parallel to the ridge, use Figure 6-18D in ASCE 7-05.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-47

3.3.3 Building EnvelopeThe following section highlights the design considerations forbuilding envelope components that have historically sustained thegreatest and most frequent damage in high winds.3.3.3.1 Exterior DoorsFor further general information on doors,see “Fenestration Systems” in the NationalInstitute of Building Sciences’ BuildingEnvelope Design Guide (www.wbdg.org/design/envelope.php)This section addresses primary and secondaryegress doors, sectional (garage) doors, androlling doors. Although blow-off of personneldoors is uncommon, it can cause seriousproblems (see Figure 3-29). Blown-off doorsallow entrance of rain and tumbling doorscan damage buildings and cause injuries.Particular attention should be given tothe design and installation of fire stationapparatus bay doors which have beenblown-in or blown-out frequently (seeFigure 3-30). If doors blow inward, theycan damage fire engines and ambulancesand impair emergency response.Blown off sectional and rolling doors are quite common. Thesefailures are typically caused by the use of door and track assembliesthat have insufficient wind resistance, or by inadequateattachment of the tracks or nailers to the wall. At the relativelynew fire station shown in Figure 3-30, twoof the windward doors were pushed out oftheir tracks. At the third door, the track waspushed out from the nailer. With the collapseof these doors, the apparatus bay wasfully pressurized. Because the connectionsbetween the trusses and the beam were tooweak to accommodate the uplift load, theentire roof structure over the apparatus bayblew off.See Section 3.4.3.1 for critical facilities located in hurricaneproneregions.Loads and ResistanceThe IBC requires that the door assembly (i.e., door, hardware,frame, and frame attachment to the wall) be of sufficient strengthto resist the positive and negative design wind pressure. Designprofessionals should require that doors comply with windload testing in accordance with ASTM E 1233. Design profes-3-48 MAKING CRITICAL FACILITIES SAFE FROM High Wind

sionals should also specify the attachmentof the door frame to the wall (e.g., type,size, spacing, and edge distance of framefasteners). For sectional and rolling doors attachedto wood nailers, design professionalsshould also specify the attachment of thenailer to the wall.For design guidance on attachment of doorframes, see Technical Data Sheet #161,Connecting Garage Door Jambs to BuildingFraming, published by the Door & AccessSystems Manufacturers Association, 2003(available at www.dasma.com).Figure 3-29:Door on a hospitalpenthouse blown off itshinges during HurricaneKatrina (Mississippi, 2005)Figure 3-30:The roof structure overthe apparatus bay blewoff following the failure ofsectional doors. HurricaneCharley (Florida, 2004)MAKING CRITICAL FACILITIES SAFE FROM High Wind3-49

Water InfiltrationWhere corrosion is problematic, anodizedaluminum or galvanized doors and frames,and stainless steel frame anchors andhardware are recommended.For primary swinging entry/exit doors,exit door hardware is recommended tominimize the possibility of the doors beingpulled open by wind suction. Exit hardwarewith top and bottom rods is more securethan exit hardware that latches at the jamb.Heavy rain that accompanies high winds (e.g., thunderstorms,tropical storms, and hurricanes) can cause significant winddrivenwater infiltration problems. The magnitude of theproblem increases with the wind speed. Leakage can occur betweenthe door and its frame, the frameand the wall, and between the thresholdand the door. When wind speeds approach120 mph, some leakage should be anticipatedbecause of the very high windpressures and numerous opportunities forleakage path development.The following recommendations should be considered to minimizeinfiltration around exterior doors.Vestibule: Adding a vestibule allows both the inner and outer doorsto be equipped with weatherstripping. The vestibule can be designedwith water-resistant finishes (e.g., concrete or tile) and thefloor can be equipped with a drain. In addition, installing exteriorthreshold trench drains can be helpful (openings must be smallenough to avoid trapping high-heeled shoes). Note that trenchdrains do not eliminate the problem, since water can still penetrateat door edges.Door swing: Out-swinging doors have weatherstripping on the interiorside of the door, where it is less susceptible to degradation,which is an advantage when compared toin-swinging doors. Some interlocking weatherstrippingassemblies are available forout-swinging doors.The successful integration of the door frameand the wall is a special challenge whendesigning doors. See Section 3.3.3.2 for discussionof this juncture.ASTM E 2112 provides information pertaining to the installationof doors, including the use of sill pan flashings with end dams andrear legs (see Figure 3-31). It is recommended that designers useASTM E 2112 as a design resource.3-50 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Figure 3-31:Door sill pan flashing with end dams, rear leg,and turned-down front legWeatherstrippingA variety of pre-manufactured weatherstripping components isavailable, including drips, door shoes and bottoms, thresholds,and jamb/head weatherstripping.Drips: These are intended to shed water away from the opening betweenthe frame and the door head, and the opening between thedoor bottom and the threshold (see Figures 3-32 and 3-33). Alternatively,a door sweep can be specified (see Figure 3-33). Forhigh-traffic doors, periodic replacement of the neoprene componentswill be necessary.Figure 3-32:Drip at door head and drip with hook at headFigure 3-33:Door shoe with drip and vinyl seal (left).Neoprene door bottom sweep (right)MAKING CRITICAL FACILITIES SAFE FROM High Wind3-51

Door shoes and bottoms: These are intended to minimize the gapbetween the door and the threshold. Figure 3-33 illustrates a doorshoe that incorporates a drip. Figure 3-34 illustrates an automaticdoor bottom. Door bottoms can be surface-mounted or mortised.For high-traffic doors, periodic replacement of the neoprene componentswill be necessary.Figure 3-34:Automatic door bottomThresholds: These are available to suit a variety of conditions.Thresholds with high (e.g., 1-inch) vertical offsets offer enhancedresistance to wind-driven water infiltration. However,the offset is limited where the thresholds are required to complywith the Americans with Disabilities Act (ADA), or at high-trafficdoors. At other doors, high offsets are preferred.Thresholds can be interlocked with the door (see Figure 3-35), or thresholds can have a stop and seal (see Figure 3-36). Insome instances, the threshold is set directly on the floor. Wherethis is appropriate, setting the threshold in butyl sealant is recommendedto avoid water infiltration between the thresholdand the floor. In other instances, the threshold is set on a panflashing, as previously discussed in this section. If the thresholdhas weep holes, specify that the weep holes not be obstructed(see Figure 3-35).Figure 3-35:Interlocking threshold with drain panFigure 3-36:Threshold with stop and seal3-52 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Adjustable jamb/head weatherstripping: This type of weatherstrippingis recommended because the wide sponge neoprene offersgood contact with the door (see Figure 3-37). The adjustmentfeature also helps to ensure good contact, provided the proper adjustmentis maintained.Meeting stile: At the meeting stile of pairs of doors, an overlappingastragal weatherstripping offers greater protection than weatherstrippingthat does not overlap.3.3.3.2 Windows and SkylightsThis section addresses general design considerations for exteriorwindows and skylights in critical facilities. For additional informationon windows and skylights in critical facilities located inhurricane-prone regions, see Section 3.4.3.2, and for those in tornado-proneregions, see Section 3.5.Figure 3-37:Adjustable jamb/headweatherstrippingLoads and ResistanceThe IBC requires that windows, curtain walls,For further general information on windows,and skylight assemblies (i.e., the glazing,see the National Institute of Buildingframe, and frame attachment to the wallSciences’ Building Envelope Design Guideor roof) have sufficient strength to resist(www.wbdg.org/design/envelope.php).the positive and negative design wind pressure(see Figure 3-38). Design professionalsshould specify that these assemblies complywith wind load testing in accordance with ASTM E 1233. It isimportant to specify an adequate load path and to check its continuityduring submittal review.Water InfiltrationHeavy rain accompanied by high winds can cause wind-drivenwater infiltration problems. The magnitude of the problemincreases with the wind speed. Leakage can occur at the glazing/frame interface, the frame itself, or between the frame and wall.When the basic wind speed is greater than 120 mph, because ofthe very high design wind pressures and numerous opportunitiesfor leakage path development, some leakage should be anticipatedwhen the design wind speed conditions are approached.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-53

Figure 3-38:Two complete windows,including frames, blewout as a result of aninadequate number offasteners. Typhoon Paka(Guam, 1997)Where corrosion is a problem, use ofanodized aluminum or stainless steelframes and stainless steel frame anchorsand screws are recommended.The maximum test pressure used in thecurrent ASTM test standard for evaluatingresistance of window units to wind-drivenrain is well below design wind pressures.Therefore, units that demonstrate adequatewind-driven rain resistance during testingmay experience leakage during actualwind events.The successful integration of windows and curtain walls into exteriorwalls is a challenge in protecting against water infiltration.To the extent possible when detailing the interface betweenthe wall and the window or curtain wall units, designers shouldrely on sealants as the secondary line of defenseagainst water infiltration, rather thanmaking the sealant the primary protection.If a sealant joint is the first line of defense, asecond line of defense should be designed tointercept and drain water that drives past thesealant joint.When designing joints between walls and windows and curtain wallunits, consider the shape of the sealant joint (i.e., a square jointis typically preferred) and the type of sealantto be specified. The sealant joint should bedesigned to enable the sealant to bond ononly two opposing surfaces (i.e., a backer rodor bond-breaker tape should be specified).Butyl is recommended as a sealant for concealedjoints, and polyurethane for exposedjoints. During installation, cleanliness of thesealant substrate is important (particularly ifpolyurethane or silicone sealants are specified),as is the tooling of the sealant. ASTM3-54 MAKING CRITICAL FACILITIES SAFE FROM High Wind

E 2112 provides guidance on the design ofsealant joints, as well as other informationpertaining to the installation of windows, includingthe use of sill pan flashings with enddams and rear legs (see Figure 3-39). Windowsthat do not have nailing flanges shouldtypically be installed over a pan flashing. Itis recommended that designers use ASTM E2112 as a design resource.Sealant joints can be protected with a removablestop, as illustrated in Figure 3-40.The stop protects the sealant from directexposure to the weather and reduces thepossibility of wind-driven rain penetration.Where water infiltration protection is particularlydemanding and important, it is recommended that onsitewater infiltration testing in accordance with ASTM E 1105 bespecified.Figure 3-39:View of a typical window sill pan flashing withend dams and rear legsSource: ASTM E 2112Figure 3-40:Protecting sealant with astop retards weatheringand reduces the exposureto wind-driven rain.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-55

For further general information on nonload-bearingwalls and wall coverings, seethe National Institute of Building Sciences’Building Envelope Design Guide(www.wbdg.org/design/envelope.php).3.3.3.3 Non-Load-Bearing Walls, WallCoverings, and SoffitsThis section addresses exterior non-load-bearing walls, exteriorwall coverings, and soffits, as well as the underside of elevatedfloors, and provides guidance for interiornon-load-bearing masonry walls. See Section3.4.3.3 for additional information pertainingto critical facilities located in hurricaneproneregions, and Section 3.5 for additionalinformation pertaining to critical facilities locatedin tornado-prone regions.Loads and ResistanceThe IBC requires that soffits, exterior non-load-bearing walls, andwall coverings have sufficient strength to resist the positive andnegative design wind pressures.To ensure the continuity of elevator service, elevator penthouse walls must possess adequatewind and water resistance. If the walls blow away or water leaks through the wall system, theelevator controls and/or motors can be destroyed. Loss of elevators may critically affect facilityoperations because the restoration can take weeks even with expedited work (see Figure 3-41).Figure 3-41:The wall covering blewoff the penthouse at thishospital complex allowingrainwater to destroythe elevator controls.Hurricane Ivan (Florida,2004)3-56 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Soffits: Depending on the wind direction,soffits can experience either positive or negativepressure. Besides the cost of repairing steel fasteners are recommended for wallWhere corrosion is a problem, stainlessthe damaged soffits, wind-borne soffit debriscan cause property damage and injuries (e.g., furring, blocking, struts, and hangers),and soffit systems. For other components(see Figure 3-42). Failed soffits may also providea convenient path for wind-driven rain stainless steel, or steel with a minimum ofnonferrous components (such as wood),to enter the building. Storm-damage researchhas shown that water blown into attic recommended. Additionally, access panelsG-90 hot-dipped galvanized coating arespaces after the loss of soffits caused significantdamage and the collapse of ceilings. soffit cavities can be periodically inspectedare recommended so components withinAt the relatively new fire station shown in for corrosion or dry rot.Figure 3-43, essentially all of the perforatedaluminum soffit was blown away. Winddrivenwater entered the attic and saturated the batt insulation,which caused the ceiling boards to collapse. After the storm, thefire station was evacuated solely because of this damage. Evenin instances where soffits remain in place, water can penetratethrough soffit vents and cause damage. At this time, there are noknown specific test standards or design guidelines to help designwind- and water-resistant soffits and soffit vents.Figure 3-42:This suspended metalsoffit was not designedfor upward-acting windpressure. Typhoon Paka(Guam, 1997)MAKING CRITICAL FACILITIES SAFE FROM High Wind3-57

Figure 3-43:This fire station wasabandoned afterHurricane Charleybecause of soffit failure.(Florida, 2004)Exterior non-load-bearing masonry walls: Particular careshould be given to the design and construction ofexterior non-load-bearing masonry walls. Althoughthese walls are not intended to carry gravity loads,they should be designed to resist the external andinternal loading for components and cladding in order to avoidcollapse. When these types of walls collapse, they represent a severerisk to life because of their great weight (see Figure 3-15).Interior non-load-bearing masonry walls: Special considerationshould also be given to interior non-load-bearing masonry walls.Although these walls are not required by building codes to be designedto resist wind loads, if the exterior glazing is broken, orthe exterior doors are blown away, the interior walls could be subjectedto significant load as the building rapidly becomes fullypressurized. To avoid casualties, it is recommended that interiornon-load-bearing masonry walls adjacent to occupied areas be designedto accommodate loads exerted by a design wind event,using the partially enclosed pressure coefficient (see Figure 3-44).By doing so, wall collapse may be prevented if the building envelopeis breached. This recommendation is applicable to criticalfacilities located in areas with a basic wind speed greater than 1203-58 MAKING CRITICAL FACILITIES SAFE FROM High Wind

mph, those used for hurricane shelters, and to critical facilities intornado-prone regions that do not have shelter space designed inaccordance with FEMA 361.Figure 3-44:The red arrows show the original location ofa CMU wall that nearly collapsed following arolling door failure. Hurricane Charley (Florida,2004)Wall CoveringsThere are a variety of exterior wall coverings. Brick veneer, exteriorinsulation finish systems (EIFS), stucco, metal wall panels, andaluminum and vinyl siding have often exhibited poor wind performance.Veneers (such as ceramic tile and stucco) over concrete,stone veneer, and cement-fiber panels and siding have also blownoff. Wood siding and panels rarely blow off. Although tilt-up precastwalls have failed during wind storms, precast wall panelsattached to steel or concrete framed buildings typically offer excellentwind performance.Brick veneer: 8 Brick veneer is frequently blown off walls duringhigh winds. When brick veneer fails, wind-driven water can enterand damage buildings, and building occupants can be vulnerableto injury from wind-borne debris (particularly if the walls are8. The brick veneer discussion is from Attachment of Brick Veneer in High-Wind Regions - Hurricane Katrina Recovery Advisory (FEMA,December 2005).MAKING CRITICAL FACILITIES SAFE FROM High Wind3-59

sheathed with plastic foam insulation or wood fiberboard in lieuof wood panels). Pedestrians in the vicinity of damaged walls canalso be vulnerable to injury from falling bricks (see Figure 3-45).Common failure modes include tie (anchor) fastener pull-out(see Figure 3-46), failure of masons to embed ties into the mortar(Figure 3-47), poor bonding between ties and mortar, a mortar ofpoor quality, and tie corrosion.Figure 3-45:The brick veneer failureon this building wasattributed to tie corrosion.Hurricane Ivan (Florida,2004)Figure 3-46:This tie remainedembedded in the mortarjoint while the smooth-shanknail pulled from the stud.3-60 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Figure 3-47:These four ties werenever embedded into themortar joint.Ties are often installed before brick laying begins. When this isdone, ties are often improperly placed above or below the mortarjoints. When misaligned, the ties must be angled up or down tobe embedded into the mortar joints (Figure 3-48). Misalignmentnot only reduces the embedment depth, but also reduces theeffectiveness of the ties, because wind forces do not act in paralleldirection to the ties.Figure 3-48:Misalignm ent of the tiereduces the embedmentand promotes veneerfailure.Corrugated ties typically used in residential and nursing home veneerconstruction provide little resistance to compressive loads.The use of compression struts would likely be beneficial, but off-MAKING CRITICAL FACILITIES SAFE FROM High Wind3-61

the-shelf devices do not currently exist. Two-piece adjustable ties(Figure 3-49) provide significantly greater compressive strengththan corrugated ties.Figure 3-49:Examples of two-pieceadjustable tiesThe following Brick Industry Association (BIA) technical notesprovide guidance on brick veneer: Technical Notes 28: AnchoredBrick Ve- neer, Wood Frame Construction (2002); Technical Notes28B: Brick Veneer/Steel Stud Walls (2005); and Technical Notes 44B:Wall Ties (2003) (available online at www.bia.org). These technicalnotes provide attachment recommendations; however, they arenot specific for high-wind regions. To enhance wind performanceof brick veneer, the following are recommended:m Calculate wind loads and determine tie spacing in accordancewith the latest edition of the Building Code Requirements forMasonry Structures, ACI 530/ASCE 5/TMS 402 (ACI 530,1996)). A stud spacing of 16 inches on center is recommendedso that ties can be anchored at this spacing.m Ring-shank nails are recommended in lieu of smooth-shank nailsfor wood studs. A minimum embedment of 2 inches is suggested.m For use with wood studs, two-piece adjustable ties arerecommended. However, where corrugated steel ties areused, they should be 22-gauge minimum, 7 / 8-inch wide by 6-inch long, and comply with ASTM A 1008, with a zinc coatingcomplying with ASTM A 153 Class B2. For ties used with steelstuds, see BIA Technical Notes 28B, Brick Veneer/Steel Stud Walls.Stainless steel ties should be used for both wood and steelstuds in areas within 3,000 feet of the coast.3-62 MAKING CRITICAL FACILITIES SAFE FROM High Wind

m Install ties as the brick is laid so that the ties are properlyaligned with the mortar joints.m Locate ties within 8 inches of door and window openings, andwithin 12 inches of the top of veneer sections.m Although corrugated ties are not recommended, if used, bendthe ties at a 90-degree angle at the nail head to minimize tieflexing when the ties are loaded in tension or compression(Figure 3-50).Figure 3-50:Bend ties at nail headsm Embed ties in joints so that the mortar completelyencapsulates the ties. Embed a minimum of 1½ inches intothe bed joint, with a minimum mortar cover of 5 / 8-inch to theoutside face of the wall (see Figure 3-51).Figure 3-51:Tie embedmentMAKING CRITICAL FACILITIES SAFE FROM High Wind3-63

To avoid water leaking into the building, it is important that weepholes be adequately spaced and not be blocked during brick installation,and that through-wall flashings be properly designedand installed. At the hospital shown in Figure 3-52, water leakedinto the building along the base of many of the brick veneer walls.When high winds accompany heavy rain, a substantial amount ofwater can be blown into the wall cavity.Figure 3-52:Water leaked inside alongthe base of the brickveneer walls. HurricaneKatrina (Louisiana, 2005)EIFS: Figure 3-53 shows typical EIFS assemblies. Figures 3-41, 3-54,and 4-6 show EIFS blow-off. In these cases, the molded expandedpolystyrene (MEPS) was attached to gypsum board, which in turnwas attached to metal studs. The gypsum board detached fromthe studs, which is a common EIFS failure. When the gypsumboard on the exterior side of the studs is blown away, it is commonfor gypsum board on the interior side to also be blown off. Theopening allows the building to become fully pressurized and allowsthe entrance of wind-driven rain. Other common types of failureinclude wall framing failure, separation of the MEPS from its substrate,and separation of the synthetic stucco from the MEPS.3-64 MAKING CRITICAL FACILITIES SAFE FROM High Wind

At the hospital shown in Figure 3-55, the EIFS was applied over aconcrete wall. The MEPS debonded from the concrete. In general,a concrete substrate prevents wind and water from entering abuilding, but if the EIFS debonds from the concrete, EIFS debriscan break unprotected glazing.Figure 3-53:Typical EIFS assembliesMAKING CRITICAL FACILITIES SAFE FROM High Wind3-65

Figure 3-54:EIFS blow-off at buildingcorner. In places, metalfascia was also blown in.Tornado (Oklahoma, 1999)Figure 3-55:EIFS blown off a cast-inplaceconcrete wall. Notethe damaged rooftopductwork. Hurricane Ivan(Florida, 2004)Wind-borne EIFS debris can be devastating to unprotectedglazing. At the hospital shown in Figure 3-56, the hospital’s originalconcrete wall panels had been furred with metal hat channelsand covered with EIFS. In a large corner area, the EIFS andgypsum board substrate blew off the hat channels and broke alarge number of windows in the multi-story connecting walkway3-66 MAKING CRITICAL FACILITIES SAFE FROM High Wind

etween the hospital and the medical office building (MOB). TheEIFS debris also broke a large number of windows in the MOB(see Figure 3-56). Glass shards from the MOB punctured the roofmembrane over the dialysis unit. The costly damage resulted inloss of several rooms in the MOB and hampered functioning ofthe hospital complex.Figure 3-56:EIFS debris blown offthe hospital building inthe background (redsquare) broke numerouswindows in the MOB inthe foreground. HurricaneIvan (Florida, 2004)Reliable wind performance of EIFS is very demandingon the designer and installer, as wellas the maintenance of EIFS and associatedsealant joints in order to minimize the reductionof EIFS’ wind resistance due to waterinfiltration. It is strongly recommended thatEIFS be designed with a drainage system thatallows the dissipation of water leaks. For furtherinformation on EIFS performance duringhigh winds and design guidance see FEMA 489and 549.Another issue associated with EIFS is the potential for judgment errors.EIFS applied over studs is sometimes mistaken for a concretewall, which may lead people to seek shelter behind it. However, insteadof being protected by several inches of concrete, only twolayers of gypsum board (i.e., one layer on each side of the studs)MAKING CRITICAL FACILITIES SAFE FROM High Wind3-67

and a layer of MEPS separate the occupants from the impact ofwind-borne debris that can easily penetrate such a wall and causeinjury.Stucco: Wind performance of traditional stucco walls is similar tothe performance of EIFS, as shown in Figure 3-57. In several areasthe metal stud system failed; in other areas the gypsum sheathingblew off the studs; and in other areas, the metal lath blew off thegypsum sheathing. The failure shown in Figure 3-57 illustrates theimportance of designing and constructing wall framing (includingattachment of stud tracks to the building and attachment of thestuds to the tracks) to resist the design wind loads.Figure 3-57:The stucco wall failure wascaused by inadequateattachment betweenthe stud tracks and thebuilding’s structure.Hurricane Ivan (Florida,2004)Metal wall panels: Wind performance of metal wall panels is highlyvariable. Performance depends on the strength of the specifiedpanel (which is a function of material and thickness, panel profile,panel width, and whether the panel is a composite) and the adequacyof the attachment (which can either be by concealed clipsor exposed fasteners). Excessive spacing between clips/fastenersis the most common problem. Clip/fastener spacing should bespecified, along with the specific type and size of fastener. Figures3-14 and 3-58 illustrate metal wall panel problems. At the schoolshown in Figure 3-58 (which was being used as a shelter), the3-68 MAKING CRITICAL FACILITIES SAFE FROM High Wind

metal panels were attached with concealed fasteners. The panelsunlatched at the standing seams. In addition to generating windbornedebris, loss of panels allowed wind-driven rain to enter thebuilding.Figure 3-58:The loss of metal wallpanels allowed asubstantial amount of winddrivenrain to penetratethis building. HurricaneIvan (Florida, 2004)To minimize water infiltration at metal wall panel joints, it is recommendedthat sealant tape be specified at sidelaps when thebasic wind speed is in excess of 90 mph. However, endlaps shouldbe left unsealed so that moisture behind the panels can be wickedaway. Endlaps should be a minimum of 3 inches (4 inches wherethe basic wind speed is greater than 120 mph) to avoid winddrivenrain infiltration. At the base of thewall, a 3-inch (4-inch) flashing should also bedetailed, or the panels should be detailed tooverlap with the slab or other components bya minimum of 3 inches (4 inches).Vinyl siding: Vinyl siding blow-off is typicallycaused by nails spaced too far apart and/orthe use of vinyl siding that has inadequatewind resistance. Vinyl siding is availablewith enhanced wind resistance features,such as an enhanced nailing hem, greaterinterlocking area, and greater thickness.The Vinyl Siding Institute (VSI) sponsorsa Certified Installer Program thatrecognizes individuals with at least 1year of experience who can demonstrateproper vinyl siding application. If vinylsiding is specified, design professionalsshould consider specifying that the sidingcontractor be a VSI-certified installer. Forfurther information on this program, seewww.vinylsiding.org.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-69

Secondary line of protection: Almost all wall coverings permit thepassage of some water past the exterior surface of the covering,particularly when the rain is wind-driven. For this reason, mostwall coverings should be considered water-shedding, rather thanwaterproofing coverings. To avoid moisture-related problems,it is recommended that a secondary line of protection with amoisture barrier (such as housewrap or asphalt-saturated felt)and flashings around door and window openings be provided.Designers should specify that horizontal laps of the moisturebarrier be installed so that water is allowed to drain from thewall (i.e., the top sheet should lap over the bottom sheet so thatwater running down the sheets remains on their outer surface).The bottom of the moisture barrier needs to be designed toallow drainage. Had the metal wall panels shown in Figure 3-58been applied over a moisture barrier and sheathing, the amountof water entering the building would have likely been eliminatedor greatly reduced.In areas that experience frequent wind-driven rain, incorporatinga rain screen design, by installing vertical furring stripsbetween the moisture barrier and siding materials, will facilitatedrainage of water from the space between the moisture barrierand backside of the siding. In areas that frequently experiencestrong winds, enhanced flashing is recommended. Enhancementsinclude use of flashings that have extra-long flanges,and the use of sealant and tapes. Flashing design should recognizethat wind-driven water could be pushed up vertically.The height to which water can be pushed increases with windspeed. Water can also migrate vertically and horizontally by capillaryaction between layers of materials (e.g., between a flashingflange and housewrap). Use of a rain screen design, in conjunctionwith enhanced flashing design, is recommended in areasthat frequently experience wind-driven rain or strong winds. Itis recommended that designers attempt to determine what typeof flashing details have successfully been used in the area wherethe facility will be constructed.Underside of Elevated FloorsIf sheathing is applied to the underside of joists or trusses elevatedon piles (e.g., to protect insulation installed between thejoists/trusses), its attachment should be specified in order to3-70 MAKING CRITICAL FACILITIES SAFE FROM High Wind

avoid blow-off. Stainless steel or hot-dip galvanized nails or screwsare recommended. Since ASCE 7 does not provide guidance forload determination, professional judgment in specifying attachmentis needed.3.3.3.4 Roof SystemsBecause roof covering damage has historicallybeen the most frequent and the costliesttype of wind damage, special attention needsto be given to roof system design. See Section3.4.3.4 for additional information pertainingto critical facilities located in hurricaneproneregions, and Section 3.5 for criticalfacilities located in tornado-prone regions.For further general information on roofsystems, see the National Institute ofBuilding Sciences’ Building EnvelopeDesign Guide (www.wbdg.org/design/envelope.php).Code RequirementsThe IBC requires the load resistance of the roof assembly tobe evaluated by one of the test methods listed in IBC’s Chapter15. Design professionals are cautioned that designs that deviatefrom the tested assembly (either with material substitutions orchange in thickness or arrangement) may adversely affect thewind performance of the assembly. The IBC does not specify aminimum safety factor. However, for the roof system, a safetyfactor of 2 is recommended. To apply the safety factor, dividethe test load by 2 to determine the allowable design load.Conversely, multiply the design load by 2 to determine the minimumrequired test resistance.For structural metal panel systems, the IBC requires test methodsUL 580 or ASTM E 1592. It is recommendedthat design professionals specify use of E1592, because it gives a better representationof the system’s uplift performance capability.The roof of the elevator penthouse mustpossess adequate wind and waterresistance to ensure continuity of elevatorservice. It is recommended that asecondary roof membrane, as discussedin Section 3.3.3.3, be specified over theelevator penthouse roof deck.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-71

Load ResistanceFM Global (FMG) is the name of theFactory Mutual Insurance Company and itsaffiliates. One of FMG’s affiliates, FactoryMutual Research (FMR) provides testingservices, produces documents that can beused by designers and contractors, anddevelops test standards for constructionproducts and systems. FMR evaluatesroofing materials and systems for resistanceto fire, wind, hail, water, foot traffic andcorrosion. Roof assemblies and componentsare evaluated to establish acceptable levelsof performance. Some documents andactivities are under the auspices of FMGand others are under FMR.Specifying the load resistance is commonly done by specifying aFactory Mutual Research (FMR) rating, such as FM 1-75. The firstnumber (1) indicates that the roof assembly passed the FMR testsfor a Class 1 fire rating. The second number (75) indicates the upliftresistance in pounds per square foot (psf) that the assemblyachieved during testing. With a safety factor of two this assemblywould be suitable for a maximum design uplift load of 37.5 psf.The highest uplift load occurs at the roof corners because ofbuilding aerodynamics as discussed in Section 3.1.3. The perimeterhas a somewhat lower load, while the field of the roof has thelowest load. FMG Property Loss Prevention Data Sheets are formattedso that a roof assembly can be selected for the field of theroof. For the perimeter and corner areas, FMGData Sheet 1-29 provides three options: 1) usethe FMG Approval Guide listing if it includesa perimeter and corner fastening method; 2)use a roof system with the appropriate FMG Approvalrating in the field, perimeter, and corner,in accordance with Table 1 in FMG Data Sheet1-29; or 3) use prescriptive recommendationsgiven in FMG Data Sheet 1-29.When perimeter and corner uplift resistancevalues are based on a prescriptive method ratherthan testing, the field assembly is adjusted tomeet the higher loads in the perimeter and cornersby increasing the number of fasteners ordecreasing the spacing of adhesive ribbons bya required amount. However, this assumes thatthe failure is the result of the fastener pullingout from the deck, or that the failure is in the vicinityof the fastener plate, which may not be the case. Also, theincreased number of fasteners required by FMG may not be sufficientto comply with the perimeter and corner loads derived fromthe building code. Therefore, if FMG resistance data are specified,it is prudent for the design professional to specify the resistance foreach zone of the roof separately. Using the example cited above,if the field of the roof is specified as 1-75, the perimeter would bespecified as 1-130 and the corner would be specified as 1-190.3-72 MAKING CRITICAL FACILITIES SAFE FROM High Wind

If the roof system is fully adhered, it is not possible to increasethe uplift resistance in the perimeter and corners. Therefore, forfully adhered systems, the uplift resistance requirement should bebased on the corner load rather than the field load.Roof System PerformanceStorm-damage research has shown that sprayed polyurethanefoam (SPF) and liquid-applied roof systems are very reliablehigh-wind performers. If the substrate to which the SPF or liquidappliedmembrane is applied does not lift, it is highly unlikelythat these systems will blow off. Both systems are also more resistantto leakage after missile impact damage than most othersystems. Built-up roofs (BURs) and modified bitumen systemshave also demonstrated good wind performance provided theedge flashing/coping does not fail (which happens frequently).The exception is aggregate surfacing, which is prone to blow-off(see Figures 3-12 and 3-13). Modified bitumen applied to a concretedeck has demonstrated excellent resistance to progressivepeeling after blow-off of the metal edge flashing. Metal panel performanceis highly variable. Some systems are very wind-resistant,while others are quite vulnerable.Of the single-ply attachment methods, the paver-ballasted andfully adhered methods are the least problematic. Systems withaggregate ballast are prone to blow-off, unless care is taken inspecifying the size of aggregate and the parapet height (see Figure3-9). The performance of protected membrane roofs (PMRs) witha factory-applied cementitious coating over insulation boards ishighly variable. When these boards are installed over a loose-laidmembrane, it is critical that an air retarder be incorporated to preventthe membrane from ballooning and disengaging the boards.ANSI/SPRI RP-4 (which is referenced in the IBC) provides windguidance for ballasted systems using aggregate, pavers, and cementitious-coatedboards.The National Research Council of Canada, Institute for Researchin Construction’s Wind Design Guide for Mechanically AttachedFlexible Membrane Roofs (B1049, 2005) provides recommendationsrelated to mechanically attached single-ply and modifiedbituminous systems. B1049 is a comprehensive wind design guideMAKING CRITICAL FACILITIES SAFE FROM High Wind3-73

that includes discussion on air retarders. Air retarders can beeffective in reducing membrane flutter, in addition to being beneficialfor use in ballasted single-ply systems. When a mechanicallyattached system is specified, careful coordination with the structuralengineer in selecting deck type and thickness is important.If a steel deck is selected, it is critical to specify that the membranefasteners be attached in rows perpendicular to the steel flangesto avoid overstressing the attachment of the deck to the deck supportstructure. At the school shown in Figure 3-59, the fastenerrows of the mechanically attached single-ply membrane ran parallelto the top flange of the steel deck. The deck fasteners wereoverstressed and a portion of the deck blew off and the membraneprogressively tore. At another building, shown in Figure 3-60, themembrane fastener rows also ran parallel to the top flange of thesteel deck. When membrane fasteners run parallel to the flange,the flange with membrane fasteners essentially carries all the upliftload because of the deck’s inability to transfer any significantload to adjacent flanges. Hence, at the joists shown in Figure 3-60,the deck fasteners on either side of the flange with the membranefasteners are the only connections to the joist that are carryingsubstantial uplift load.Figure 3-59:The orientation of themembrane fastener rowsled to blow-off of the steeldeck. Hurricane Marilyn(U.S. Virgin Islands, 1995)3-74 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Figure 3-60:View of the underside ofa steel deck showing themechanically attachedsingle-ply membranefastener rows runningparallel to, instead ofacross, the top flange ofthe deck.For metal panel roof systems, the following are recommended:m When clip or panel fasteners are attached to nailers, detail theconnection of the nailer to the nailer support (including thedetail of where nailers are spliced over a support).m When clip or panel fasteners are loaded in withdrawal(tension), screws are recommended in lieu of nails.m For concealed clips over a solid substrate, it is recommendedthat chalk lines be specified so that the clips are correctlyspaced.m When the basic wind speed is 110 mph or greater, it isrecommended that two clips be used along the eaves, ridges,and hips.m For copper panel roofs in areas with a basic wind speed greaterthan 90 mph, it is recommended that Type 316 stainless steelclips and stainless steel screws be used in lieu of copper clips.m Close spacing of fasteners is recommended at hip and ridgeflashings (e.g., spacing in the range of 3 to 6 inches on center,commensurate with the design wind loads.)MAKING CRITICAL FACILITIES SAFE FROM High Wind3-75

Edge Flashings and CopingsRoof membrane blow-off is almost always a result of lifting andpeeling of the metal edge flashing or coping, which serves toclamp down the membrane at the roof edge. Therefore, it is importantfor the design professional to carefully consider thedesign of metal edge flashings, copings, and the nailers to whichthey are attached. The metal edge flashing on the modifiedbitumen membrane roof shown in Figure 3-61 was installed underneaththe membrane, rather than on top of it, and then strippedin. In this location, the edge flashing was unable to clamp themembrane down. At one area, the membrane was not sealed tothe flashing. An ink pen was inserted into the opening prior tophotographing to demonstrate how wind could catch the openingand lift and peel the membrane.Figure 3-61:The ink pen shows anopening that the windcan catch, and causelifting and peeling of themembrane.ANSI/SPRI ES-1, Wind Design Standard for Edge Systems Used in LowSlope Roofing Systems (2003) provides general design guidance includinga methodology for determining the outward-acting loadon the vertical flange of the flashing/coping (ASCE 7 does notprovide this guidance). ANSI/SPRI ES-1 is referenced in the IBC.ANSI/SPRI ES-1 also includes test methods for assessing flashing/coping resistance. This manual recommends a minimum safetyfactor of 3 for edge flashings, copings, and nailers for critical facil-3-76 MAKING CRITICAL FACILITIES SAFE FROM High Wind

ities. For FMG-insured facilities, FMR-approved flashing should beused and FM Data Sheet 1-49 should also be consulted.The traditional edge flashing/coping attachment method relieson concealed cleats that can deform under wind load and lead todisengagement of the flashing/coping (see Figure 3-62) and subsequentlifting and peeling of the roof membrane (as shown inFigure 3-12). When a vertical flange disengages and lifts up, theedge flashing and membrane are very susceptible to failure. Normally,when a flange lifts such as shown in Figure 3-62, the failurecontinues to propagate and the metal edge flashing and roofmembrane blows off.Storm-damage research has revealed that, in lieu of cleat attachment,the use of exposed fasteners to attach the vertical flangesof copings and edge flashings has been found to be a very effectiveand reliable attachment method. The coping shown inFigure 3-63 was attached with ¼-inch diameter stainless steel concretespikes at 12 inches on center. When the fastener is placedin wood, #12 stainless steel screws with stainless steel washers arerecommended. The fasteners should be more closely spaced inthe corner areas (the spacing will depend upon the design windloads). ANSI/SPRI ES-1 provides guidance on fastener spacingand thickness of the coping and edge flashing.Figure 3-62:The metal edge flashingdisengaged from thecontinuous cleat andthe vertical flange lifted.Hurricane Hugo (SouthCarolina, 1989)MAKING CRITICAL FACILITIES SAFE FROM High Wind3-77

Figure 3-63:Both vertical faces of thecoping were attached withexposed fasteners insteadof concealed cleats.Typhoon Paka (Guam,1997)GuttersStorm-damage research has shown that gutters are seldom constructedto resist wind loads (see Figure 3-64). When a gutter lifts,it typically causes the edge flashing that laps into the gutter to liftas well. Frequently, this results in a progressive lifting and peelingof the roof membrane. The membrane blow-off shown in Figure3-65 was initiated by gutter uplift. The gutter was similar to thatshown in Figure 3-64. The building, housing the county Sheriff’soffice, suffered water leakage that shut down the county 911 callcenter, destroyed the crime lab equipment, and caused significantinterior water damage.Figure 3-64:This gutter, supportedby a type of bracket thatprovides no significantuplift resistance, failedwhen wind lifted ittogether with the metaledge flashing that lappedinto the gutter. HurricaneFrancis (Florida, 2004)3-78 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Figure 3-65:The original modifiedbitumen membrane wasblown away after thegutter lifted in the areashown by the red arrow(the black membrane is atemporary roof). HurricaneFrancis (Florida, 2004)Special design attention needs to be given to attaching guttersto prevent uplift, particularly for those in excess of 6 inches inwidth. Currently, there are no standards pertaining to gutterwind resistance. It is recommended that the designer calculatethe uplift load on gutters using the overhang coefficient fromASCE 7. There are two approaches to resist gutter uplift.m Gravity-support brackets can be designed to resist upliftloads. In these cases, in addition to being attached at itstop, the bracket should also be attached at its low end to thewall. The gutter also needs to be designed so it is attachedsecurely to the bracket in a way that will effectively transferthe gutter uplift load to the bracket. Bracket spacing willdepend on the gravity and uplift load, the bracket’s strength,and the strength of connections between the gutter/bracketand the bracket/wall. With this option, the bracket’s top willtypically be attached to a wood nailer, and that fastener willbe designed to carry the gravity load. The bracket’s lowerconnection will resist the rotational force induced by gutteruplift. Because brackets are usually spaced close togetherto carry the gravity load, developing adequate connectionstrength at the lower fastener is generally not difficult.m The other option is to use gravity-support brackets only toresist gravity loads, and use separate sheet-metal straps at 45-degree angles to the wall to resist uplift loads. Strap spacingMAKING CRITICAL FACILITIES SAFE FROM High Wind3-79

will depend on the gutter uplift load and strength of theconnections between the gutter/strap and the strap/wall.Note that FMG Data Sheet 1-49 recommends placing straps10 feet apart. However, at that spacing with wide gutters,fastener loads induced by uplift are quite high. When strapsare spaced at 10 feet, it can be difficult to achieve sufficientlystrong uplift connections.When designing a bracket’s lower connection to awall or a strap’s connection to a wall, designers shoulddetermine appropriate screw pull-out values. With thisoption, a minimum of two screws at each end of a strap isrecommended. At a wall, screws should be placed side byside, rather than vertically aligned, so the strap load is carriedequally by the two fasteners. When fasteners are verticallyaligned, most of the load is carried by the top fastener.Since the uplift load in the corners is much higher than the loadbetween the corners, enhanced attachment is needed in cornerareas regardless of the option chosen. ASCE 7 provides guidanceabout determining a corner area’s length.Parapet Base FlashingsInformation on loads for parapet base flashings was first introducedin the 2002 edition of ASCE 7. The loads on base flashingsare greater than the loads on the roof covering if the parapet’s exteriorside is air-permeable. When base flashing is fully adhered,it has sufficient wind resistance in most cases. However, when baseflashing is mechanically fastened, typical fastening patterns maybe inadequate, depending on design wind conditions (see Figure3-66). Therefore, it is imperative that the base flashing loads becalculated, and attachments be designed to accommodate theseloads. It is also important for designers to specify the attachmentspacing in parapet corner regions to differentiate them from theregions between corners.3-80 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Figure 3-66:If mechanically attachedbase flashings havean insufficient numberof fasteners, the baseflashing can be blownaway. Hurricane Andrew(Florida, 1992)Steep-Slope Roof CoveringsFor a discussion of wind performance of asphalt shingle and tileroof coverings, see FEMA 488 (2005), 489 (2005), and 549 (2006).For recommendations pertaining to asphalt shingles and tiles, seeFact Sheets 19, 20, and 21 in FEMA 499 (2005).3.3.4 Nonstructural Systems andEquipmentNonstructural systems and equipment include all componentsthat are not part of the structural system or building envelope. Exterior-mountedmechanical equipment (e.g., exhaust fans, HVACunits, relief air hoods, rooftop ductwork, and boiler stacks), electricalequipment (e.g., light fixtures and lightning protectionsystems), and communications equipment (e.g., antennae andsatellite dishes) are often damaged during high winds. Damagedequipment can impair the operation of the facility, the equipmentcan detach and become wind-borne missiles, and water can enterthe facility where equipment was displaced (see Figures 3-20, 3-67,3-68, 3-72, 3-76, and 3-78). The most common problems typicallyrelate to inadequate equipment anchorage, inadequate strengthof the equipment itself, and corrosion.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-81

Figure 3-67:Toppled rooftopmechanical equipment.Hurricane Andrew(Florida, 1992)Figure 3-68:This gooseneck wasattached with only twosmall screws. A substantialamount of water wasable to enter the buildingduring Hurricane Francis.(Florida, 2004)See Section 3.4.4 for additional information pertaining to criticalfacilities located in hurricane-prone regions.3.3.4.1 Exterior-Mounted Mechanical EquipmentThis section discusses loads and attachment methods, as well asthe problems of corrosion and water infiltration.3-82 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Loads and Attachment Methods 9Information on loads on rooftop equipment was first introducedin the 2002 edition of ASCE 7. For guidance on load calculations,see “Calculating Wind Loads and Anchorage Requirements forRooftop Equipment” (ASHRAE, 2006). A minimum safety factorof 3 is recommended for critical facilities. Loads and resistanceshould also be calculated for heavy pieces of equipment since thedead load of the equipment is often inadequate to resist the designwind load. The 30’ x 10’ x 8’ 18,000-pound HVAC unit shownin Figure 3-69 was attached to its curb with 16 straps (one screwper strap). Although the wind speeds were estimatedto be only 85 to 95 miles per hour(peak gust), the HVAC unit blew off the medicaloffice building.To anchor fans, small HVAC units, and reliefair hoods, the minimum attachmentschedule provided in Table 3-2 is recommended.The attachment of the curb to theroof deck also needs to be designed and constructedto resist the design loads.Mechanical penetrations through theelevator penthouse roof and walls mustpossess adequate wind and waterresistance to ensure continuity of elevatorservice (see Section 3.3.3.3). In additionto paying special attention to equipmentattachment, air intakes and exhaustsshould be designed and constructed toprevent wind-driven water from enteringthe penthouse.Figure 3-69:Although this 18,000-pound HVAC unit wasattached to its curb with16 straps, it blew offduring Hurricane Ivan.(Florida, 2004)9. Discussion is based on: Attachment of Rooftop Equipment in High-wind Regions—Hurricane Katrina Recovery Advisory (May 2006,revised July 2006)MAKING CRITICAL FACILITIES SAFE FROM High Wind3-83

Table 3-2: Number of #12 Screws for Base Case Attachment of Rooftop EquipmentCase No Curb Size and Equipment Type Equipment AttachmentFastener Factorfor Each Side ofCurb or Flange12345612” x 12” Curb with GooseneckRelief Air Hood12” x 12” Gooseneck Relief AirHood with Flange12” x 12” Gooseneck Relief AirHood with Flange24” x 24” Curb with GooseneckRelief Air Hood24” x 24” Gooseneck Relief AirHood with Flange24” x 24” Gooseneck Relief AirHood with FlangeHood Screwed to Curb 1.6Flange Screwed to 22 GaugeSteel Roof DeckFlange Screwed to 15/32” OSBRoof Deck2.82.9Hood Screwed to Curb 4.6Flange Screwed to 22 GaugeSteel Roof DeckFlange Screwed to 15/32” OSBRoof Deck7 24” x 24” Curb with Exhaust Fan Fan Screwed to Curb 2.58 36” x 36” Curb with Exhaust Fan Fan Screwed to Curb 3.39105’-9” x 3’- 8” Curb with 2’- 8”high HVAC Unit5’-9 ”x 3’- 8” Curb with 2’- 8”high Relief Air Hood8.18.2HVAC Unit Screwed to Curb 4.5*Hood Screwed to Curb 35.6*Notes to Table 3-2:1. The loads are based on ASCE 7-05. The resistance includes equipment weight.2. The Base Case for the tabulated numbers of #12 screws (or ¼ pan-head screws for flange-attachment) is a 90-mph basic windspeed, 1.15 importance factor, 30’ building height, Exposure C, using a safety factor of 3.V 2 D( )3. For other basic wind speeds, multiply the tabulated number of #12 screws by to determine the required number90 2of #12 screws (or ¼ pan-head screws) required for the desired basic wind speed, V D(mph).4. For other roof heights up to 200’, multiply the tabulated number of #12 screws by (1.00 + 0.003 [h - 30]) to determine therequired number of #12 screws or ¼ pan-head screws for buildings between 30’ and 200’.Example A: 24” x 24” exhaust fan screwed to curb (table row 7), Base Case conditions (see Note 1): 2.5 screws per side;therefore, round up and specify 3 screws per side.Example B: 24” x 24” exhaust fan screwed to curb (table row 7), Base Case conditions, except 120 mph: 120 2 x 1 ÷ 90 2 =1.78 x 2.5 screws per side = 4.44 screws per side; therefore, round down and specify 4 screws per side.Example C: 24” x 24” exhaust fan screwed to curb (table row 7), Base Case conditions, except 150’ roof height: 1.00 +0.003 (150’ - 30’) = 1.00 + 0.36 = 1.36 x 2.5 screws per side = 3.4 screws per side; therefore, round down and specify 3screws per side.* This factor only applies to the long sides. At the short sides, use the fastener spacing used at the long sides.3-84 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Fan cowling attachment: Fans are frequentlyTo avoid corrosion-induced failure (seeblown off their curbs because they are poorlyFigure 3-78), it is recommended thatattached. When fans are well attached, theexterior-mounted mechanical, electrical,cowlings frequently blow off (see Figureand communications equipment be3-70). Blown off cowlings can tear roof membranesand break glazing. Unless the fanmade of nonferrous metals, stainlesssteel, or steel with minimum G-90 hot-dipmanufacturer specifically engineered thegalvanized coating for the equipmentcowling attachment to resist the design windbody, stands, anchors, and fasteners.load, cable tie-downs (see Figure 3-71) areWhen equipment with enhanced corrosionrecommended to avoid cowling blow-off.protection is not available, the designerFor fan cowlings less than 4 feet in diameter,1 / 8-inch diameter stainless steel cablesshould advise the building owner thatperiodic equipment maintenance andare recommended. For larger cowlings, useinspection is particularly important to3/ 16-inch diameter cables. When the basicavoid advanced corrosion and subsequentwind speed is 120 mph or less, specify two cables.Where the basic wind speed is greaterequipment damage during a windstorm.than 120 mph, specify four cables. To minimizeleakage potential at the anchor point,it is recommended that the cables be adequately anchored tothe equipment curb (rather than anchored to the roof deck).The attachment of the curb itself also needs to be designed andspecified.Figure 3-70:Cowlings blew off twoof the fans on a policebuilding that housed thecounty’s EOC. HurricaneIvan (Florida, 2004)MAKING CRITICAL FACILITIES SAFE FROM High Wind3-85

Figure 3-71:Cables were attached toprevent the cowling fromblowing off. Typhoon Paka(Guam, 1997)Ductwork: To avoid wind and wind-borne debris damage to rooftopductwork, it is recommended that ductwork not be installed onthe roof (see Figure 3-72). If ductwork is installed on the roof, itis recommended that the ducts’ gauge and the method of attachmentbe able to resist the design wind loads.Figure 3-72:Two large openingsremained (circled areaand inset to the left) afterthe ductwork on this roofblew away. HurricaneKatrina (Mississippi, 2005)3-86 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Condenser attachment: In lieu of placingrooftop-mounted condensers on woodsleepers resting on the roof (see Figure 3-73), it is recommended that condensersbe anchored to equipment stands. The attachmentof the stand to the roof deck alsoneeds to be designed to resist the designloads. In addition to anchoring the base ofthe condenser to the stand, two metal strapswith two side-by-side #12 screws or boltswith proper end and edge distances at eachstrap end are recommended when the basicwind speed is greater than 90 mph (seeFigure 3-74).Three publications pertaining to seismicrestraint of equipment provide general informationon fasteners and edge distances:m Installing Seismic Restraints forMechanical Equipment (FEMA 412,2002)m Installing Seismic Restraints forElectrical Equipment (FEMA 413,2004)m Installing Seismic Restraints for Ductand Pipe (FEMA 414, 2004)Figure 3-73:Sleeper-mountedcondensers displaced byhigh winds. HurricaneKatrina (Mississippi, 2005)Vibration isolators: If vibration isolators are used to mount equipment,only those able to resist design uplift loads should bespecified and installed, or an alternative means to accommodateuplift resistance should be provided (see Figure 3-75).MAKING CRITICAL FACILITIES SAFE FROM High Wind3-87

Figure 3-74:This condenser hadsupplemental attachmentstraps (see red arrows).Typhoon Paka (Guam,1997)Figure 3-75:Failure of vibrationisolators that providedlateral resistance but nouplift resistance causedequipment damage.A damaged vibrationisolator is shown in theinset. Hurricane Katrina(Mississippi, 2005)3-88 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Boiler and exhaust stack attachment: To avoid wind damage to boilerand exhaust stacks, wind loads on stacks should be calculated andguy-wires should be designed and constructed to resist the loads.Toppled stacks, as shown at the hospital in Figure 3-76, can allowwater to enter the building at the stack penetration, damage theroof membrane, and become wind-borne debris. The designershould advise the building owner that guy-wires should be inspectedannually to ensure they are taut.Figure 3-76:Three of the five stacksthat did not have guywireswere blown down.Hurricane Marilyn (U.S.Virgin Islands, 1995)Access panel attachment: Equipment access panels frequently blowoff. To minimize this, job-site modifications, such as attachinghasps and locking devices like carabiners, are recommended.The modification details need to be customized. Detailed designmay be needed after the equipment has been delivered to the jobsite. Modification details should be approved by the equipmentmanufacturer.Equipment screens: Screens around rooftop equipment are frequentlyblown away (see Figure 3-77). Screens should be designedto resist the wind load derived from ASCE 7. Since the effect ofscreens on equipment wind loads is unknown, the equipment attachmentbehind the screens should be designed to resist thedesign load.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-89

Figure 3-77:Equipment screen panels,such as these blown awayat a hospital, can breakglazing, puncture roofmembranes, and causeinjury. Hurricane Ivan(Florida, 2004)Water InfiltrationDuring high winds, wind-driven rain can be driven through airintakes and exhausts unless special measures are taken. Louversshould be designed and constructed to prevent leakage betweenthe louver and wall. The louver itself should be designed to avoidwater being driven past the louver. However, it is difficult to preventinfiltration during very high winds. Designing sumps withdrains that will intercept water driving past louvers or air intakesshould be considered. ASHRAE 62.1 (2004) provides some informationon rain and snow intrusion. The Standard 62.1 User’sManual provides additional information, including examples andillustrations of various designs.3.3.4.2 Exterior-Mounted Electrical andCommunications EquipmentDamage to exterior-mounted electrical equipment is infrequent,mostly because of its small size (e.g., disconnect switches). Exceptionsinclude communication towers, surveillance cameras,electrical service masts, satellite dishes, and lightning protectionsystems. The damage is typically caused by inadequate mountingas a result of failure to perform wind load calculations and anchoragedesign. Damage is also sometimes caused by corrosion(see Figure 3-78 and the text box on corrosion in Section 3.3.4.1).3-90 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Figure 3-78:Collapsed hospital lightfixtures caused by severecorrosion (see inset).Hurricane Ivan (Florida,2004)Communication towers and poles: ANSI/C2 provides guidance fordetermining wind loads on power distribution and transmissionpoles and towers. AASHTO LTS-4-M (amended by LTS-4-12,2001 and 2003, respectively) provides guidance for determiningwind loads on light fixture poles (standards).Both ASCE 7 and ANSI/TIA-222-G contain wind load provisionsfor communication towers (structures). The IBC allows the useof either approach. The ASCE wind load provisions are generallyconsistent with those contained in ANSI/TIA-222-G. ASCE 7,however, contains provisions for dynamically sensitive towers thatare not present in the ANSI/TIA standard. ANSI/TIA classifiestowers according to their use (Class I, Class II, and Class III). Thismanual recommends that towers (including antennae) that aremounted on, located near, or serve critical facilities be designed asClass III structures.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-91

Collapse of both large and small communication towers at emergencyoperation centers, fire and police stations, and hospitalsis quite common during high-wind events (see Figures 3-79 and3-80). These failures often result in complete loss of communicationcapabilities. In addition to the disruption of communications,collapsed towers can puncture roof membranes and allow waterleakage into the facilities, unless the roof system incorporateda secondary membrane (as discussed in Section 3.4.3.4). At thetower shown in Figure 3-79 the anchor bolts were pulled out ofthe deck, which resulted in a progressive peeling of the fully adheredsingle-ply roof membrane. Tower collapse can also injure orkill people.See Section 3.3.1.1 regarding site considerations for light fixturepoles, power poles, and electrical and communications towers.Figure 3-79:The collapse of the antennatower caused progressivepeeling of the roofmembrane. Also note thatthe exhaust fan blew off thecurb, but the high parapetkept it from blowing off theroof. Hurricane Andrew(Florida, 1992)3-92 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Figure 3-80:The antenna tower atthis fire station buckled.Hurricane Katrina(Mississippi, 2005)Electrical service masts: Service mast failure is typically caused bycollapse of overhead power lines, which can be avoided by usingunderground service. Where overhead service is provided, it isrecommended that the service mast not penetrate the roof. Otherwise,a downed service line could pull on the mast and rupture theroof membrane.Satellite dishes: For the satellite dish shown in Figure 3-81, thedish mast was anchored to a large metal pan that rested on theroof membrane. CMU was placed on the pan to provide overturningresistance. This anchorage method should only be usedwhere calculations demonstrate that it provides sufficient resistance.In this case the wind approached the satellite dish insuch a way that it experienced very little wind pressure. In hurricane-proneregions, use of this anchorage method is notrecommended (see Figure 3-82).Lightning protection systems: For attachment of lightning protectionsystems on buildings higher than 100 feet above grade, andfor buildings located where the basic wind speed is in excess of 90mph, see Section 3.4.4.3.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-93

Figure 3-81:Common anchoringmethod for satellite dish.Hurricane Ivan (Florida,2004)Figure 3-82:A satellite dish anchoredsimilarly to that shownin Figure 3-81 wasblown off of this fivestorybuilding. HurricaneCharley (Florida, 2004)The recommendations given in Section 3.3 are summarized inTable 3-3.3-94 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Table 3-3: Risk Reduction Design MethodsSite and General Design See Section 3.3.1ExposurePresence of trees or polesSite accessLocate in Exposure B if possible. Avoid escarpments andupper half of hills.Locate to avoid blow-down on facility.Minimum of two roads.General design issues See recommendations in Section 3.3.1.2.Wind loads on MWFRS, building envelope androoftop equipmentLoad resistanceDurabilityRain penetrationUse ASCE 7 or local building code, whichever procedureresults in highest loads.Determine via calculations and/or text data. Give loadresistance criteria in contract documents, and clearly indicateload path continuity.Give special attention to material selection and detailingto avoid problems of corrosion, wood decay, and termiteattack.Detail to minimize wind-driven rain penetration into thebuilding.Structural Systems (MWFRS) See Section 3.3.2Pre-engineered metal buildingsExterior load-bearing wallsRoof decksTake special steps to ensure structure is not vulnerable toprogressive collapse.Design as MWFRS and C&C. Reinforce CMU. Sufficientlyconnect precast concrete panels.Concrete, steel, or wood sheathing is recommended. Attachsteel decks with screws. Use special fasteners for woodsheathing. Anchor precast concrete to resist wind loads. IfFMG-rated assembly, deck must comply with FMG criteria.Walkways and canopies Use pressure coefficients from ASCE 7.Exterior Doors See Section 3.3.3.1Door, frame, and frame fastenersMust be able to resist positive and negative design load,verified by ASTM E 1233 testing. Specify type, size, andspacing of frame fasteners.Water infiltrationConsider vestibules, door swing, and weatherstripping. Referto ASTM E 2112 (2001) for design guidance.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-95

Table 3-3: Risk Reduction Design Methods (continued)Windows and Skylights See Section 3.3.3.2Glazing, frame, and frame fastenersWater infiltrationNon-Load-Bearing Walls, Wall Coverings,and SoffitsExterior non-load-bearing walls, wall coverings,soffits, and elevated floorsLoad resistanceElevator penthousesSoffitsMust be able to resist positive and negative design load,verified by ASTM E 1233 (2000) testing. Specify type, size,and spacing of frame fasteners.Carefully design junctures between walls and windows/curtain walls. Avoid relying on sealant as the first or onlyline of defense. Refer to ASTM E 2112 for design guidance.Where infiltration protection is demanding, conduct onsitewater infiltration testing per ASTM E 1105 (2000).See Section 3.3.3.3See recommendations in Section 3.3.3.3Must be able to resist positive and negative design load.Design as C&C.Design to prevent water infiltration at walls, roof, andmechanical penetrations.Design to resist wind and wind-driven water infiltration.Interior non-load-bearing masonry walls Design for wind load per Section 3.3.3.3.Brick veneer See recommendations in Section 3.3.3.3.Secondary protectionProvide moisture barrier underneath wall coverings that arewater-shedding.Roof Systems See Section 3.3.3.4TestingLoad resistance for field, perimeter, and cornerareasEdge flashings and copingsGuttersSystem selectionAvoid designs that deviate from a tested assembly. Ifdeviation is evident, perform rational analysis. For structuralmetal panel systems, test per ASTM E 1592 (2000).Specify requirements. See recommendations in Section3.3.3.4.Follow ANSI/SPRI ES-1 (2003). Use a safety factor of three.Calculate loads and design attachment to resist uplift.Select systems that offer high reliability, commensurate withthe wind-regime at facility location.3-96 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Table 3-3: Risk Reduction Design Methods (continued)Roof Systems (continued) See Section 3.3.3.4Mechanically attached modified bitumen andsingle-ply membrane systemsRefer to Wind Design Guide for Mechanically AttachedFlexible Membrane Roofs, B1049 (NRCC, 2005).Metal panel systems See recommendations in Section 3.3.3.4.Parapet base flashingCalculate loads and resistance. This is particularly importantif base flashing is mechanically attached.Asphalt shingles and tile coverings See Fact Sheets 19, 20, or 21 in FEMA 499.Exterior-mounted Mechanical, Electrical, andCommunications EquipmentLoad resistanceEquipment strengthRooftop satellite dishesSee Section 3.3.4Specify anchorage of all rooftop and wall-mountedequipment. Use a safety factor of three for equipmentanchorage. See recommendations in Section 3.3.4.1.Specify cable tie-downs for fan cowlings. Specify haspsand locking devises for equipment access panels. Seerecommendations in Section 3.3.4.1.Design the attachment to resist the design wind loads.Antennae towers See recommendations in Section 3.3.4.2.After Completing Contract Documents See Section 3.3.1Peer reviewSubmittalsField observationsConsider peer review of contract documents. See Section3.3.1.2.Ensure required documents are submitted, includingall necessary information. Verify that each submittaldemonstrates the load path through the system and into itssupporting element. See Section 3.3.1.3.Analyze design to determine which elements are critical toensuring high-wind performance. Determine observationfrequency of critical elements. See Section 3.3.1.3.Post-occupancy inspections, maintenance, andrepairAdvise the building owner of the importance of periodicinspections, special inspections after unusually high winds,maintenance, and timely repair. See Section 3.3.1.4.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-97

3.4 BEST PRACTICES IN HURRICANE-PRONE REGIONSThis section presents the general design and constructionpractice recommendations for critical facilities located inhurricane-prone regions. These recommendations are additionalto the ones presented in Section 3.3 and in many casessupersede those recommendations. Critical facilities located inhurricane-prone regions require special design and constructionattention because of the unique characteristics of this typeof windstorm. Hurricanes can bring very high winds that last formany hours, which can lead to material fatigue failures. The variabilityof wind direction increases the probability that the wind willapproach the building at the most critical angle. Hurricanes alsogenerate a large amount of wind-borne debris, which can damagevarious building components and cause injury and death.Although all critical facilities in hurricane-prone regions requirespecial attention, three types of facilities are particularly importantbecause of their function or occupancy: EOCs, healthcarefacilities, and shelters. EOCs serve as centralized managementhubs for emergency operations. The loss of an EOC can severelyaffect the overall response and recovery in the area. Healthcarefacilities normally have vulnerable occupants (patients) at thetime of a hurricane, and afterwards, many injured people seekmedical care. Significant damage to a facility can put patients atrisk and jeopardize delivery of care to those seeking treatment.Shelters often have a large number of occupants. The collapseof a shelter building or entrance of wind-borne debris intoa shelter has the potential to injure or kill many people. See3-98 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Chapter 4 for information on the performance of some EOCs,healthcare facilities, shelters, and other types of critical facilitiesthat were affected by Hurricane Katrina.In order to ensure continuity of service during and after hurricanes,the design, construction, and maintenance of the followingcritical facilities should be very robust to provide sufficient resiliencyto withstand the effects of hurricanes.EOCs: Communications are important for most types of criticalfacilities, but for EOCs they are vital. To inhibit disruption of operations,water infiltration that could damage electrical equipmentmust be prevented, antenna towers need to be strong enoughto resist the wind, and the emergency and standby power systemneeds to remain operational.Healthcare facilities: Full or partial evacuation of a hospital priorto, during, or after a hurricane, is time consuming, expensive,and for some patients, potentially life-threatening. Water infiltrationthat could damage electrical equipmentor medical supplies, or inhibit the use ofcritical areas (such as operating rooms andnursing floors) needs to be prevented. Theemergency and standby power systems needto remain operational and be adequatelysized to power all needed circuits, includingthe HVAC system. Provisions are needed forwater and sewer service in the event of loss ofmunicipal services, and antenna towers needto be strong enough to resist the wind.Shelters: During and after hurricanes, these facilities are oftenoccupied by more than 1,000 people. The primary purpose ofshelters is to protect occupants from injury or death as a resultof building collapse or entrance of wind-borne debris. However,beyond meeting this basic requirement, providing a degree ofoccupant comfort during a stressful time is important. The building’sdesign and construction should avoid significant waterinfiltration and provide at least a minimum level of lighting andmechanical ventilation using emergency generators. Sheltersshould also have provisions for sewage service (such as portabletoilets) in the event of loss of municipal water or sewer service.Nursing homes are often no morehurricane-resistant than residential buildings.Evacuating these facilities (particularlyskilled nursing homes and facilities caringfor patients with Alzheimer’s disease) canbe difficult. Except for antenna towers, theissues identified for hospitals are applicableto nursing homes.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-99

FEMA recommends that shelters be designed in accordance withFEMA 361, Design and Construction Guidance for Community Shelters(2000).3.4.1 Site and General DesignConsiderationsVia ASCE 7, the 2006 edition of the IBC has only one special windrelatedprovision pertaining to Category III and IV buildings inhurricane-prone regions. It pertains to glazing protection withinwind-borne debris regions (as defined in ASCE 7). This single additionalrequirement does not provide adequate protection foroccupants of a facility during a hurricane, nor does it ensure acritical facility will remain functional during and after a hurricane.A critical facility may comply with IBC but still remain vulnerableto water and missile penetration through the roof or walls. To provideoccupant protection, the exterior walls and the roof must bedesigned and constructed to resist wind-borne debris as discussedin Sections 3.4.2 and 3.4.3.The following recommendations are made regarding siting:m Locate poles, towers, and trees with trunks larger than 6 inchesin diameter away from primary site access roads so that they donot block access to, or hit, the facility if toppled.m Determine if existing buildings within 1,500 feet of the newfacility have aggregate surfaced roofs. If roofs with aggregatesurfacing are present, it is recommended that the aggregate beremoved to prevent it from impacting the new facility. Aggregateremoval may necessitate reroofing or other remedial workin order to maintain the roof’s fire or wind resistance.m In cases where multiple buildings, such as hospitals or schoolcampuses, are occupied during a storm, it is recommendedthat enclosed walkways be designed to connect the buildings.The enclosed walkways (above- or below-grade) are particularlyimportant for protecting people moving between buildingsduring a hurricane (e.g., to retrieve equipment or supplies) orfor situations when it is necessary to evacuate occupants fromone building to another during a hurricane.3-100 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Figure 3-83:Open walkways donot provide protectionfrom wind-borne debris.Hurricane Katrina(Mississippi, 2005)3.4.2 Structural SystemsBecause of the exceptionally good wind performance and windbornedebris resistance that reinforced cast-in-place concretestructures offer, a reinforced concrete roof deck and reinforcedconcrete or reinforced and fully grouted CMU exterior walls arerecommended as follows:Roof deck: A minimum 4-inch thick cast-in-place reinforced concretedeck is the preferred deck. Other recommended decksare minimum 4-inch thick structural concrete topping over steeldecking, and precast concrete with an additional minimum 4-inchstructural concrete topping.If these recommendations are not followedfor critical facilities located in areas wherethe basic wind speed is 100 mph or greater,it is recommended that the roof assemblybe able to resist complete penetration of thedeck by the “D” missile specified in ASTM E1996 (2005, see text box in Section 3.4.3.1).If precast concrete is used for the roof orwall structure, the connections should becarefully designed, detailed, andconstructed.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-101

Exterior load-bearing walls: A minimum 6-inch thick cast-in-placeconcrete wall reinforced with #4 rebars at 12 inches on centereach way is the preferred wall. Other recommended walls are aminimum 8-inch thick fully grouted CMU reinforced with #4 rebarsin each cell, and precast concrete that is a minimum 6 inchesthick and reinforced equivalent to the recommendations for castin-placewalls.3.4.3 Building EnvelopeThe design considerations for building envelope components ofcritical facilities in hurricane-prone regions include a number ofadditional recommendations. The principal concern that must beaddressed is the additional risk from wind-borne debris and waterleakage, as discussed below.3.4.3.1 Exterior DoorsAlthough the ASCE-7 wind-borne debris provisions only applyto glazing within a portion of hurricane-prone regions, it is recommendedthat all critical facilities located where the basicwind speed is 100 mph or greater comply with the followingrecommendations:m To minimize the potential for missiles penetrating exteriordoors and striking people inside the facility, it is recommendedthat doors (with and without glazing) be designed to resist the“E” missile load specified in ASTM E 1996. The doors shouldbe tested in accordance with ASTM E 1886 (2005). The testassembly should include the door, door frame, and hardware.m It is recommended that the doors on shelters meet the windpressure and missile resistance criteria found in FEMA 361.Information on door assemblies that meet these criteria isincluded in FEMA 361.3-102 MAKING CRITICAL FACILITIES SAFE FROM High Wind

ASTM E 1996 specifies five missile categories, A through E. The missiles are of various weightsand fired at various velocities during testing. Building type (critical or non-critical) and basicwind speed determine the missiles required for testing. Of the five missiles, the E missile hasthe greatest momentum. Missile E is required for critical facilities located where the basic windspeed is greater than or equal to 130 mph. Missile D is permitted where the basic wind speed isless than130 mph. FEMA 361 also specifies a missile for shelters. The shelter missile has muchgreater momentum than the D and E missiles, as shown below:Missile Missile Weight Impact Speed MomentumASTM E 1996—D9 pound 2x4 lumber50 feet per second(34 mph)14 lb f-s*ASTM E 1996—E9 pound 2x4 lumber80 feet per second(55 mph)22 lb f-s*FEMA 361 (Shelter Missile)15 pound 2x4 lumber147 feet per second(100 mph)68 lb f-s**lb f-s = pounds force per second3.4.3.2 Windows and SkylightsExterior glazing that is not impact-resistant (such as laminatedglass or polycarbonate) or protected by shutters is extremely susceptibleto breaking if struck by wind-borne debris. Even small,low-momentum missiles can easily break glazing that is not protected(see Figures 3-84 and 3-85). At the hospital shown inFigure 3-84, approximately 400 windows were broken. Most ofthe breakage was caused by wind-blown aggregate from the hospital’saggregate ballasted single-ply membrane roofs, and aggregatefrom built-up roofs. With broken windows, a substantial amount ofwater can be blown into a building, and the internal air pressurecan be greatly increased (as discussed in Section 3.1.3) which maydamage the interior partitions and ceilings.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-103

Figure 3-84:Plywood panels (blackcontinuous bands) installedafter the glass spandrelpanels were broken byroof aggregate. HurricaneKatrina (Mississippi, 2005)Figure 3-85:A small piece of asphaltshingle (red arrow) brokethe window at this nursinghome. Hurricane Katrina(Mississippi, 2005)In order to minimize interior damage, the IBC, through ASCE 7,prescribes that exterior glazing in wind-borne debris regions beimpact-resistant, or be protected with an impact-resistant covering(shutters). For Category III and IV buildings in areas with a basicwind speed of 130 mph or greater, the glazing is required to resista larger momentum test missile than would Category II buildingsand Category III and IV buildings in areas with wind speeds of lessthan 130 mph.3-104 MAKING CRITICAL FACILITIES SAFE FROM High Wind

ASCE 7 refers to ASTM E 1996 for missile loads and to ASTM E1886 for the test method to be used to demonstrate compliancewith the E 1996 load criteria. In addition to testing impact resistance,the window unit is subjected to pressure cycling after testmissile impact to evaluate whether the window can still resistwind loads. If wind-borne debris glazing protection is providedby shutters, the glazing is still required by ASCE 7 to meet thepositive and negative design air pressures.Although the ASCE 7 wind-borne debris provisions only applyto glazing within a portion of hurricane-prone regions, it is recommendedthat all critical facilities located where the basicwind speed is 100 mph or greater comply with the followingrecommendations:m To minimize the potential for missiles penetrating exteriorglazing and injuring people, it is recommended that exteriorglazing up to 60 feet above grade be designed to resist thetest Missile E load specified in ASTM E 1996 (see text boxin Section 3.4.3.1). In addition, if roofs with aggregatesurfacing are present within 1,500 feet of the facility, glazingabove 60 feet should be designed to resist the test Missile Aload specified in ASTM E 1996. The height of the protectedglazing should extend a minimum of 30 feet above theaggregate surfaced roof per ASCE 7.Because large missiles are generally flying at lowerelevations, glazing that is more than 60 feet above grade andmeets the test Missile A load should be sufficient. However,if the facility is within a few hundred feet of anotherbuilding that may create debris such as EIFS, tiles, or rooftopequipment, it is recommended that the test Missile E load bespecified instead of the Missile A for the upper-level glazing.m For those facilities where glazing resistant to bomb blastsis desired, the windows and glazed doors can be designedto accommodate wind pressure, missile loads, and blastpressure. However, the window and door units need to betested for missile loads and cyclic air pressure, as well as forblast. A unit that meets blast criteria will not necessarily meetthe E 1996 and E 1886 criteria, and vice versa.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-105

With the advent of building codes requiringFor further information on designingglazing protection in wind-borne debrisglazing to resist blast, see the “Blastregions, a variety of shutter designs have enteredthe market. Shutters typically have aSafety” resource pages of the NationalInstitute of Building Sciences' Buildinglower initial cost than laminated glass. However,unless the shutter is permanentlyEnvelope Design Guide (www.wbdg.org/design/enve-lope.php).anchored to the building (e.g., an accordionshutter), storage space will be needed. Also,when a hurricane is forecast, costs will be incurred each time shuttersare installed and removed. The cost and difficulty of shutterdeployment and demobilization on upper-level glazing may beavoided by using motorized shutters, although laminated glassmay be a more economical solution. For further information onshutters, see Section 3.6.2.2.3.4.3.3 Non-Load-Bearing Walls, WallCoverings, and SoffitsFor buildings not constructed using concreteroof decks and concrete or CMU walls (asrecommended), shelters can be constructedwithin buildings for occupant protection.FEMA 320—Taking Shelter From theStorm: Building a Safe Room Inside YourHome (2004) describes how restroomsand storage rooms can be designed forsheltering inside new and existing buildings.It is recommended that wood-framed andpre-engineered metal buildings in areaswith a basic wind speed of 100 mph orgreater, that will be occupied during ahurricane, have a designated storageroom(s), office(s), or small conferenceroom(s) designed in accordance with FEMA320 to protect the occupants. AlthoughFEMA 320 is intended for residentialconstruction, the guidance is suitable forsmall shelters inside critical facilities such asfire and police stations. For large shelters,FEMA 361 criteria are recommended.In order to achieve enhanced missile resistanceof non-load-bearing exterior walls, thewall types discussed in Section 3.4.2 (i.e., reinforcedconcrete, or reinforced and fullygrouted CMU) are recommended.To minimize long-term problems with exteriorwall coverings and soffits, it is recommendedthat they be avoided to the maximum extentpossible. Exposed or painted reinforced concreteor CMU offers greater reliability (i.e.,they have no coverings that can blow off andbecome wind-borne debris).For all critical facilities located where thebasic wind speed is 100 mph or greater thatare not constructed using reinforced concreteor reinforced and fully grouted CMU(as is recommended in this manual), it is recommendedthat the wall system selected besufficient to resist complete penetration ofthe wall by the “E” missile specified in ASTME 1996.3-106 MAKING CRITICAL FACILITIES SAFE FROM High Wind

For interior non-load-bearing masonry walls in critical facilities locatedwhere the basic wind speed is greater than 120 mph, see therecommendations given in Section 3.3.3.3.3.4.3.4 Roof SystemsThe following types of roof systems are recommended for criticalfacilities in hurricane-prone regions, because they are more likelyto avoid water infiltration if the roof is hit by wind-borne debris,and also because these systems are less likely to become sources ofwind-borne debris:m In tropical climates where insulation is not needed above theroof deck, specify either liquid-applied membrane over cast-inplaceconcrete deck, or modified bitumen membrane torcheddirectly to primed cast-in-place concrete deck.m Install a secondary membrane over a concrete deck (ifanother type of deck is specified, a cover board may beneeded over the deck). Seal the secondary membrane atperimeters and penetrations. Specify rigid insulation overthe secondary membrane. Where the basic wind speed isup to 110 mph, a minimum 2-inch thick layer of insulationis recommended. Where the speed is between 110 and 130mph, a total minimum thickness of 3 inches is recommended(installed in two layers). Where the speed is greater than 130mph, a total minimum thickness of 4 inches is recommended(installed in two layers). A layer of 5 / 8-inch thick glass matgypsum roof board is recommended over the insulation,followed by a modified bitumen membrane. A modifiedbitumen membrane is recommended for the primarymembrane because of its somewhat enhanced resistance topuncture by small missiles compared with other types of roofmembranes.The purpose of the insulation and gypsum roof board is toabsorb missile energy. If the primary membrane is puncturedor blown off during a storm, the secondary membrane shouldprovide watertight protection unless the roof is hit withmissiles of very high momentum that penetrate the insulationand secondary membrane. Figure 3-86 illustrates the merit ofMAKING CRITICAL FACILITIES SAFE FROM High Wind3-107

specifying a secondary membrane. The copper roof blew offthe hospital’s intensive care unit (ICU). Patients and staff werefrightened by the loud noise generated by the metal panels asthey banged around during the hurricane. Fortunately therewas a very robust underlayment (a built-up membrane) thatremained in place. Since only minor leakage occurred, theICU continued to function.Figure 3-86:Because this roof systemincorporated a secondarymembrane, the ICUwas not evacuated afterthe copper roof blewoff. Hurricane Andrew(Florida, 1992)m For an SPF roof system over a concrete deck, where the basicwind speed is less than 130 mph, it is recommended thatthe foam be a minimum of 3 inches thick to avoid missilepenetration through the entire layer of foam. Where thespeed is greater than 130 mph, a 4-inch minimum thickness isrecommended. It is also recommended that the SPF be coated,rather than protected with an aggregate surfacing.m For a PMR, it is recommended that pavers weighing a minimumof 22 psf be specified. In addition, base flashings shouldbe protected with metal (such as shown in Figure 3-93) toprovide debris protection. Parapets with a 3 foot minimumheight (or higher if so indicated by ANSI/SPRI RP-4, 2002)are recommended at roof edges. This manual recommendsthat PMRs not be used for critical facilities in hurricane-proneregions where the basic wind speed exceeds 130 mph.3-108 MAKING CRITICAL FACILITIES SAFE FROM High Wind

m For structural metal roofs, it is recommendedthat a roof deck be specified,rather than attaching the panels directly topurlins as is commonly done with pre-engineeredmetal buildings. If panels blow offbuildings without roof decking, as shownin Figure 3-17, wind-borne debris and rainare free to enter the building.Roofs over rooms used to store importantrecords (such as police station evidencerooms) should incorporate secondarymembranes to avoid water leakage damage.To preclude water infiltration damage fromexterior walls, avoid locating importantstorage rooms adjacent to exterior walls.Structural standing seam metal roof panels with concealedclips and mechanically seamed ribs spaced at 12 inches oncenter are recommended. If the panels are installed over aconcrete deck, a modified bitumen secondary membrane isrecommended if the deck has a slope less than ½ :12. If thepanels are installed over a steel deck or wood sheathing, amodified bitumen secondary membrane (over a suitable coverboard when over steel decking) is recommend, followed byrigid insulation and metal panels. Where the basic wind speedis up to 110 mph, a minimum 2-inch thick layer of insulationis recommended. Where the speed is between 110 and 130mph, a total minimum thickness of 3 inches is recommended.Where the speed is greater than 130 mph, a total minimumthickness of 4 inches is recommended. Although some clipsare designed to bear on insulation, it is recommended thatthe panels be attached to wood nailers attached to the deck,because nailers provide a more stable foundation for the clips.If the metal panels are blown off or punctured during ahurricane, the secondary membrane should provide watertightprotection unless the roof is hit with missiles of very highmomentum. At the roof shown in Figure 3-87, the structuralstanding seam panel clips bore on rigid insulation over a steeldeck. Had a secondary membrane been installed over the steeldeck, the membrane would have likely prevented significantinterior water damage and facility disruption.m Based on field performance of architectural metal panels inhurricane-prone regions, exposed fastener panels are recommendedin lieu of architectural panels with concealed clips.For panel fasteners, stainless steel screws are recommended. Asecondary membrane protected with insulation is recommended,as discussed above for structural standing seam systems.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-109

Figure 3-87:Significant interior waterdamage and facilityinterruption occurredafter the standing seamroof blew off. HurricaneMarilyn (U.S. VirginIslands, 1995)In order to avoid the possibility of roofing components blowingoff and striking people arriving at a critical facility during a storm,the following roof systems are not recommended: aggregate surfacingseither on BUR (shown in Figure 3-12), single-plies (shownin Figure 3-9), or SPF; lightweight concrete pavers; cementitiouscoatedinsulation boards; slate; and tile (see Figure 3-88). Evenwhen slates and tiles are properly attached to resist wind loads,their brittleness makes them vulnerable to breakage as a resultof wind-borne debris impact. The tile and slate fragments can beblown off the roof, and fragments can damage other parts of theroof causing a cascading failure.Figure 3-88:Brittle roof coverings,like slate and tile, can bebroken by missiles, andtile debris can break othertiles. Hurricane Charley(Florida, 2004)3-110 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Mechanically attached and air-pressure equalized single-ply membranesystems are susceptible to massive progressive failure aftermissile impact, and are therefore not recommended for criticalfacilities in hurricane-prone regions. At the building shown inFigure 3-89, a missile struck the fully adhered low-sloped roof andslid into the steep-sloped reinforced mechanically attached singleplymembrane in the vicinity of the red arrow. A large area of themechanically attached membrane was blown away as a result ofprogressive membrane tearing. Fully adhered single-ply membranesare very vulnerable to missiles (see Figure 3-90) and arenot recommended unless they are ballasted with pavers.Figure 3-89:Mechanically attachedsingle-ply membraneprogressively tore afterbeing cut by windbornedebris. HurricaneAndrew (Florida, 1992)Figure 3-90:Fully adhered single-plyroof membrane struck by alarge number of missiles.Hurricane Marilyn (U.S.Virgin Islands, 1995)MAKING CRITICAL FACILITIES SAFE FROM High Wind3-111

Edge flashings and copings: If cleats are used for attachment, it isrecommended that a “peel-stop” bar be placed over the roof membranenear the edge flashing/coping, as illustrated in Figure 3-91.The purpose of the bar is to provide secondary protection againstmembrane lifting and peeling in the event that edge flashing/coping fails. A robust bar specifically made for bar-over mechanicallyattached single-ply systems is recommended. The bar needsto be very well anchored to the parapet or the deck. Dependingon design wind loads, spacing between 4 and 12 inches on centeris recommended. A gap of a few inches should be left betweeneach bar to allow for water flow across the membrane. After thebar is attached, it is stripped over with a stripping ply.Figure 3-91:A continuous peel-stop barover the membrane mayprevent a catastrophicprogressive failure if theedge flashing or coping isblown off. (Modified fromFEMA 55, 2000)Walkway pads: Roof walkway pads are frequently blown off duringhurricanes (Figure 3-92). Pad blow-off does not usually damagethe roof membrane. However, wind-borne pad debris can damageother building components and injure people. Walkway pads aretherefore not recommended in hurricane-prone regions.3-112 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Figure 3-92:To avoid walkway padblow off, as occurredon this hospital roof,walkway pads are notrecommended. HurricaneCharley (Florida, 2004)Parapets: For low-sloped roofs, minimum 3-foot high parapets arerecommended. With parapets of this height or greater, the upliftload in the corner region is substantially reduced (ASCE 7 permitstreating the corner zone as a perimeter zone). Also, a highparapet (as shown in Figures 3-78 and 3-118) may intercept windbornedebris and keep it from blowing off the roof and damagingother building components or injuring people. To protect baseflashings from wind-borne debris damage and subsequent waterleakage, it is recommended that metal panels on furring strips beinstalled over the base flashing (Figure 3-93). Exposed stainlesssteel screws are recommended for attaching the panels to the furringstrips because using exposed fasteners is more reliable thanusing concealed fasteners or clips (as were used for the failedpanels shown in Figure 3-58).MAKING CRITICAL FACILITIES SAFE FROM High Wind3-113

Figure 3-93:Base flashing protected bymetal panels attached withexposed screws. HurricaneKatrina (Mississippi, 2005)3.4.4 Nonstructural Systems andEquipmentNonstructural systems and equipment include all componentsthat are not part of the structural system or building envelope.Exterior-mounted equipment is especially vulnerable to hurricane-induceddamage, and special attention should be paid topositioning and mounting of these components in hurricaneproneregions.3.4.4.1 ElevatorsWhere interruption of elevator service would significantly disruptfacility operations, it is recommended that elevators be placed inseparate locations within the building and be served by separateelevator penthouses. This is recommended, irrespective of theelevator penthouse enhancements recommended in Sections 3.3.3and 3.3.4, because of the greater likelihood that at least one of theelevators will remain operational and therefore allow the facility tofunction as intended.3-114 MAKING CRITICAL FACILITIES SAFE FROM High Wind

3.4.4.2 Mechanical PenthousesBy placing equipment in mechanical penthouses rather thanleaving them exposed on the roof, equipment can be shieldedfrom high-wind loads and wind-borne debris. Although screens(such as shown in Figure 3-77) could be designed and constructedto protect equipment from horizontally-flying debris, they are noteffective in protecting equipment from missiles that have an angulartrajectory. It is therefore recommended that mechanicalequipment be placed inside mechanical penthouses. The penthouseitself should be designed and constructed in accordancewith the recommendations given in Sections 3.4.2 and 3.4.3.3.4.4.3 Lightning Protection Systems (LPS)Lightning protection systems frequently become disconnectedfrom rooftops during hurricanes. Displaced LPS components canpuncture and tear roof coverings, thus allowing water to leak intobuildings (see Figures 3-94 and 3-95). Prolonged and repeatedslashing of the roof membrane by loose conductors (“cables”) andpuncturing by air terminals (“lightning rods”) can result in liftingand peeling of the membrane. Also, when displaced, the LPS is nolonger capable of providing lightning protection in the vicinity ofthe displaced conductors and air terminals.Figure 3-94:A displaced air terminalthat punctured themembrane in severallocations. HurricaneMarilyn (U.S. VirginIslands, 1995)MAKING CRITICAL FACILITIES SAFE FROM High Wind3-115

Figure 3-95:View of an end of aconductor that becamedisconnected. HurricaneKatrina (Mississippi,2005)Lightning protection standards such as NFPA 780 and UL 96Aprovide inadequate guidance for attaching LPS to rooftops inhurricane-prone regions, as are those recommendations typicallyprovided by LPS and roofing material manufacturers. LPS conductorsare typically attached to the roof at 3-foot intervals. Theconductors are flexible, and when they are exposed to high winds,the conductors exert dynamic loads on the conductor connectors(“clips”). Guidance for calculating the dynamic loads does notexist. LPS conductor connectors typically have prongs to anchorthe conductor. When the connector is well-attached to the roofsurface, during high winds the conductor frequently bends backthe malleable connector prongs (see Figure 3-96). Conductor connectorshave also debonded from roof surfaces during high winds.Based on observations after Hurricane Katrina and other hurricanes,it is apparent that pronged conductor connectors typicallyhave not provided reliable attachment.Figure 3-96:The conductor deformedthe prongs under windpressure, and pulledaway from the connector.Hurricane Katrina(Mississippi, 2005)3-116 MAKING CRITICAL FACILITIES SAFE FROM High Wind

To enhance the wind performance of LPS, the following arerecommended: 10Parapet attachment: When the parapet is 12 inches high or greater,it is recommended that the air terminal base plates and conductorconnectors be mechanically attached with #12 screwsthat have minimum 1¼-inch embedment into the inside face ofthe parapet nailer and are properly sealed for watertight protection.Instead of conductor connectors that have prongs, it isrecommended that mechanically attached looped connectors beinstalled (see Figure 3-97).Figure 3-97: Thisconductor was attached tothe coping with a loopedconnector. HurricaneKatrina (Mississippi, 2005)Attachment to built-up, modified bitumen, and single-ply membranes:For built-up and modified bitumen membranes, attach the airterminal base plates with asphalt roof cement. For single-ply membranes,attach the air terminal base plates with pourable sealer (ofthe type recommended by the membrane manufacturer).In lieu of attaching conductors with conductor connectors, it isrecommended that conductors be attached with strips of membraneinstalled by the roofing contractor. For built-up andmodified bitumen membranes, use strips of modified bitumencap sheet, approximately 9 inches wide at a minimum. If strips10. Discussion is based on Rooftop Attachment of Lightning Protection Systems in High-Wind Regions—Hurricane Katrina Recover Advisory(May 2006, Revised July 2006).MAKING CRITICAL FACILITIES SAFE FROM High Wind3-117

are torch-applied, avoid overheating the conductors. For singleplymembranes, use self-adhering flashing strips, approximately 9inches wide at a minimum. Start the strips approximately 3 inchesfrom either side of the air terminal base plates. Use strips that areapproximately 3 feet long, separated by a gap of approximately 3inches (see Figure 3-98).Figure 3-98: Plan showing conductor attachmentAs an option to securing the conductors with stripping plies,conductor connectors that do not rely on prongs could be used(such as the one shown in Figure 3-99). However, the magnitudeof the dynamic loads induced by the conductor is unknown,and there is a lack of data on the resistanceprovided by adhesively-attached connectors. For thisreason, attachment with stripping plies is the preferredoption, because the plies shield the conductor fromthe wind. If adhesive-applied conductor connectorsare used, it is recommended that they be spaced moreclosely than the 3-foot spacing required by NFPA 780and UL 96A. Depending on wind loads, a spacing of 6to 12 inches on center may be needed in the corner regionsof the roof, with a spacing of 12 to 18 inches oncenter at roof perimeters (see ASCE 7 for the size ofcorner regions).Figure 3-99:Adhesively-attached conductorconnector that does not use prongs3-118 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Mechanically attached single-ply membranes: It is recommended thatconductors be placed parallel to, and within 8 inches of, membranefastener rows. Where the conductor falls between or isperpendicular to membrane fastener rows, install an additionalrow of membrane fasteners where the conductor will be located,and install a membrane cover-strip over the membrane fasteners.Place the conductor over the cover-strip and secure the conductoras recommended above.By following the above recommendations, additional rows ofmembrane fasteners (beyond those needed to attach the membrane)may be needed to accommodate the layout of theconductors. The additional membrane fasteners and coverstripshould be coordinated with, and installed by, the roofingcontractor.Standing seam metal roofs: It is recommended that pre-manufactured,mechanically attached clips that are commonly used toattach various items to roof panels be used. After anchoringthe clips to the panel ribs, the air terminal base plates and conductorconnectors are anchored to the panel clips. In lieu ofconductor connectors that have prongs, it is recommendedthat mechanically attached looped connectors be installed (seeFigure 3-97).Conductor splice connectors: In lieu of pronged splice connectors(see Figure 3-100), bolted splice connectors are recommendedbecause they provide a more reliable connection (see Figure 3-101). It is recommended that strips of flashing membrane (asrecommended above) be placed approximately 3 inches fromeither side of the splice connector to minimize conductor movementand to avoid the possibility of theconductors becoming disconnected. Toallow for observation during maintenance inspections,do not cover the connectors.It is recommended that the buildingdesigner advise the building owner tohave the LPS inspected each spring, toverify that connectors are still attached tothe roof surface, that they still engage theconductors, and that the splice connectorsare still secure. Inspections are alsorecommended after high-wind events.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-119

Figure 3-100:If conductors detach fromthe roof, they are likelyto pull out from prongedsplice connectors.Hurricane Charley(Florida, 2004)Figure 3-101:Bolted splice connectorsare recommended toprevent free ends ofconnectors from beingwhipped around bywind. Hurricane Katrina(Mississippi, 2005)3.4.5 Municipal UtilitiesHurricanes typically disrupt municipal electrical service, and oftenthey disrupt telephone (both cellular and land-line), water, andsewer services. These disruptions may last from several days to severalweeks. Electrical power disruptions can be caused by damage3-120 MAKING CRITICAL FACILITIES SAFE FROM High Wind

to power generation stations and by damaged lines, such as majortransmission lines and secondary feeders. Water disruptions canbe caused by damage to water treatment or well facilities, lack ofpower for pumps or treatment facilities, or by broken water linescaused by uprooted trees. Sewer disruptions can be caused bydamage to treatment facilities, lack of power for treatment facilitiesor lift stations, or broken sewer lines. Phone disruptions canbe caused by damage at switching facilities and collapse of towers.Critical facilities should be designed to prevent the disruption ofoperations arising from prolonged loss of municipal services.3.4.5.1 Electrical PowerIt is recommended that critical facilities that will be occupiedduring a hurricane, or will be needed within the first few weeks afterwards,be equipped with one or more emergency generators. Inaddition to providing emergency generators, it is recommendedthat one or more additional standby generators be considered,particularly for facilities such as EOCs, hospitals and nursinghomes, shelters, and fire and police stations, where continuedavailability of electrical power is vital. The purpose of providingthe standby generators is to power those circuits that are not poweredby the emergency generators. With both emergency andstandby generators, the entire facility will be completely backedup. It is recommended that the emergency generator and standbygenerator systems be electrically connected via manual transferswitches to allow for interconnectivity in the event of emergencygenerator failure. The standby circuits can be disconnected fromthe standby generators, and the emergency circuits can be manuallyadded. The emergency generators should be rated for primepower (continuous operation).Running generators for extended time periods frequently resultsin equipment failure. Thus, provisions for back-up generation capacityare important, because the municipal power system maybe out of service for many days or even weeks. Therefore, it is recommendedthat an exterior box for single pole cable cam lockingconnectors be provided so that a portable generator can be connectedto the facility. With a cam locking box, if one or more ofthe emergency or standby generators malfunction, a portablegenerator can be brought to the facility and quickly connected.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-121

It is recommended that shelters beprovided with an emergency generator tosupply power for lighting, exit signs, firealarm system, public address system, andfor mechanical ventilation. A standbygenerator is also recommended in theevent that the emergency generatormalfunctions. A cam locking box is alsorecommended to facilitate connection of aback-up portable generator.Back-up portable generators should beviewed as a third source of power (i.e., theyshould not replace standby generators), becauseit may take several days to get a back-upportable generator to the site.Generators should be placed inside windbornedebris resistant buildings (seerecommendations in Sections 3.4.2 and3.4.3) so that they are not susceptible todamage from debris or tree fall. Locatinggenerators outdoors (see Figure 4-44) or insideweak enclosures is not recommended.It is recommended that wall louvers for generators be capableof resisting the test Missile E load specified in ASTM E 1996. Alternatively,wall louvers can be protected with a debris-resistantscreen wall so that wind-borne debris is unable to penetrate thelouvers and damage the generators.It is recommended that sufficient onsite fuel storage be providedto allow all of the facility’s emergency and standby generators tooperate at full capacity for a minimum of 96 hours (4 days). 11 Ifat any time it appears that refueling won’t occur within 96 hours,provision should be made to shut off part or all the standby circuitsin order to provide longer operation of the emergencycircuits. For remote facilities or situations where it is believedthat refueling may not occur within 96 hours, the onsite fuelstorage capacity should be increased as deemed appropriate. Itis recommended that fuel storage tanks, piping, and pumps beplaced inside wind-borne debris resistant buildings, or underground.If the site is susceptible to flooding, refer to Chapter 2recommendations.3.4.5.2 Water ServiceIt is recommended that critical facilities that rely on water forcontinuity of service (especially hospitals and nursing homes)be provided with an independent water supply—a well or onsitewater storage. Facilities that only need drinking water for11. The 96-hour fuel supply is based in part on the Department of Veterans Affairs criteria.3-122 MAKING CRITICAL FACILITIES SAFE FROM High Wind

occupants can have bottled water providedinstead.If water is needed for cooling towers, the independentwater supply should be sized toaccommodate the system. It is recommendedthat the well or onsite storage be capable ofproviding an adequate water supply for firesprinklers. Alternatively, it is recommendedthat the building designer should advise thebuilding owner to implement a continual fire-watch and provideadditional fire extinguishers until the municipal water service isrestored. For hospitals, it is recommended that the well or onsitewater storage be capable of providing a minimum of 100 gallonsof potable water per day per patient bed for four days (the 100 gallonsincludes water for cooling towers). 12For critical facilities with boilers, it isrecommended to store fuel onsite for aminimum of 96 hours (4 days). Storagetanks, piping, and pumps should be insidewind-borne debris resistant buildings or beplaced underground (if site is susceptibleto flooding, refer to Chapter 2).It is recommended that pumps for wells oronsite storage be connected to an emergencypower circuit, that a valve be providedon the municipal service line, and that onsitewater treatment capability be providedwhere appropriate.For hospitals and nursing homes, it isrecommended that onsite storage ofmedical gases be sized to provide aminimum of 96 hours (4 days) of service.3.4.5.3 Sewer ServiceIt is recommended that critical facilities that rely on sewer servicefor continuity of operations (especially hospitals andnursing homes) be provided with an alternative means of wastedisposal, such as a temporary storage tank which can be pumpedout by a local contractor. For facilities such as EOCs, fire and policestations, and shelters, portable toilets can be placed insidethe facility before the onset of a hurricane. It is recommendedthat all critical facilities be provided with back-flow preventors.12. This recommendation is based on the Department of Veterans Affairs criteria.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-123

3.4.6 Post-Design ConsiderationsIn addition to adequate design, proper attention must be given toconstruction, post-occupancy inspection, and maintenance.3.4.6.1 Construction Contract AdministrationIt is important for owners of critical facilities in hurricane-proneregions to obtain the services of a professional contractor whowill execute the work described in the contract documents ina diligent and technically proficient manner. The frequency offield observations and extent of special inspections and testingshould be greater than those employed on critical facilities thatare not in hurricane-prone regions.3.4.6.2 Periodic Inspections, Maintenance, andRepairThe recommendations given in Section 3.3.1.4 for post-occupancyand post-storm inspections, maintenance, and repair arecrucial for critical facilities in hurricane-prone regions. Failureof a building component that was not maintained properly, repairedor replaced, can present a considerable risk of injury ordeath to occupants, and the continued operation of the facilitycan be jeopardized.The recommendations given in Section 3.4 are summarized inTable 3-4.3-124 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Table 3-4: Recommendations for Design of Critical FacilitiesEOCs, healthcare facilities, andsheltersSheltersWalkways between campus buildingsStructural systemsExterior wallsExterior doorsExterior windows and skylightsRoof coveringParapetsElevatorsMechanical penthousesDesign very robustly.Refer to FEMA 361, Design and Construction Guidance for CommunityShelters.If buildings will be occupied during a hurricane, provide enclosedwalkways.Use reinforced cast-in-place concrete. If the roof deck is not cast-inplace,use precast concrete or concrete topping over steel decking.Use reinforced concrete or fully grouted and reinforced CMU withoutwall coverings, other than paint.Use doors designed and tested to resist test missiles.Use laminated glass or shutters designed and tested to resist testmissiles. If equipped with shutters, glazing is still required to resist windpressure loads.Design a roof system that can accommodate missiles as recommendedin Section 3.4.3.4. Avoid aggregate surfacings, lightweight concretepavers, cementitious-coated insulation boards, slate, and tile. Avoidsingle-ply membranes unless ballasted with heavy pavers.Use minimum 3-foot high parapets for low-sloped roofs.Place elevators in separate locations served by separate penthouses.Place rooftop equipment in penthouses rather than exposed on theroof.Lightning protection systems Attach LPS to the roof as recommended in Section 3.4.4.3.Emergency power Provide emergency power as recommended in Section 3.4.5.1.Water serviceSewer serviceConstruction contract administrationPeriodic inspections, maintenance,and repairProvide a water supply independent of municipal supplies.Provide a means of waste disposal independent of municipal service.Construction executed by a professional contractor and subcontractors.Conduct more frequent field observations, special inspections andtesting.After construction, conduct diligent periodic inspections and specialinspections after storms. Ensure diligent maintenance and promptrepairs.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-125

3.5 BEST PRACTICES IN TORNADO-PRONE REGIONSStrong and violent tornadoes may reach wind speeds substantiallygreater than those recorded in the strongesthurricanes. The wind pressures that these tornadoes canexert on a building are tremendous, and far exceed the minimumpressures derived from building codes. Figure 3-102 shows aclassroom wing in a school in Illinois. All of the exterior windowswere broken, and virtually all of the cementitious wood-fiber deckpanels were blown away. Much of the metal roof decking over theband and chorus area also blew off. The gymnasium collapsed, asdid a portion of the multi-purpose room. The school was not insession at the time the tornado struck.Figure 3-102:A Northern Illinois schoolheavily damaged by astrong tornado in 19903-126 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Strong and violent tornadoes can generate very powerful missiles.Experience shows that large and heavy objects, including vehicles,can be hurled into buildings at high speeds. The missile stickingout of the roof in the foreground of Figure 3-103 is a double 2-inch by 6-inch wood member. The portion sticking out of the roofis 13 feet long. It penetrated a ballasted ethylene propylene dienemonomer (EPDM) membrane, approximately 3 inches of polyisocyanurateroof insulation, and the steel roof deck. The missilelying on the roof just beyond is a 2-inch by 10-inch by 16-foot longwood member.Figure 3-103:A violent tornadoshowered the roof ofthis school with missiles.(Oklahoma, 1999)There is little documentation regarding tornado-induced damageto critical facilities. Most of the damage reports available pertainto schools because schools are the most prevalent type of criticalfacilities and, therefore, are more likely to be struck. A 1978 reportprepared for the Veterans Administration 13 identified fourhospitals that were struck by tornadoes between 1973 and 1976.Table 3-5 (taken from that report) further illustrates the effectstornados can have on critical facilities.13. A Study of Building Damage Caused by Wind Forces, McDonald, J.R. and Lea, P.A, Institute for Disaster Research, Texas Tech University, 1978.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-127

Table 3-5: Examples of Ramifications of Tornado Damage at Four HospitalsLocation and BuildingCharacteristicsTornadoCharacteristicsDamageRamifications of DamageMountain View, Missouri (St.Francis Hospital). One-storysteel frame with non-loadbearing masonry exterior walls.The tornadocrossedover oneend of thehospital.Metal roof deckingwas blown off, somewindows were broken,and rooftop mechanicalequipment wasdisplaced.Patients were moved toundamaged areas of thehospital.Omaha, Nebraska (BishopBergen Mercy Hospital). Fivestoryreinforced concrete frame.Maximumwind speedestimated at200 mph.Proximity tohospital notdocumented.Windows werebroken, and rooftopmechanical equipmentwas damagedand displaced.Communicationsand electrical powerwere lost (emergencygenerators providedpower).A few minor cuts; “doublewalled corridors” providedprotection for patients and staff.Some incoming emergencyroom patients (injuredelsewhere in the city) werererouted to other hospitals. Lossof communications hamperedthe rerouting.Omaha, Nebraska (BishopBergen Mercy Hospital– Ambulatory Care Unit). Onestoryload bearing CMU wallswith steel joists.See above.The building was a totalloss due to wall androof collapse.Patients were evacuated tothe first floor of the mainhospital when the tornadowatch was issued.Corsicana, Texas (NavarroCounty Memorial Hospital).Five-story reinforced concreteframe with masonry non-loadbearing walls in some areas andglass curtain walls.The tornadowas veryweak.Many windows werebroken by aggregatefrom the hospital’s builtuproofs. Intake ductwork in the penthousecollapsed.Two people in the parking lotreceived minor injuries fromroof aggregate. Electricalpower was lost for 2 hours(emergency generatorsprovided power).Monahans, Texas (WardMemorial Hospital). One-storyload bearing CMU walls withsteel joists. Some areas hadmetal roof deck and others hadgypsum deck.The tornadopasseddirectly overthe hospital,withmaximumwind speedestimated at150 mph.The roof structure wasblown away on aportion of the building(the bond beampulled away from thewall). Many windowswere broken. Rooftopmechanical equipmentwas damaged.3-128 MAKING CRITICAL FACILITIES SAFE FROM High Wind

For critical facilities located in tornado-prone regions (as definedin Section 3.2.2), the following are recommended:m Incorporate a shelter within the facility to provide occupantprotection. For shelter design, FEMA 361 criteria arerecommended.m For interior non-load-bearing masonry walls, see therecommendations given in Section 3.3.3.3.m Brick veneer, aggregate roof surfacing, roof pavers, slate, andtile cannot be effectively anchored to prevent them frombecoming missiles if a strong or violent tornado passes neara building with these components. To reduce the potentialnumber of missiles, and hence reduce the potential forbuilding damage and injury to people, it is recommended thatthese materials not be specified for critical facilities in tornadoprone regions.m For hospitals, nursing homes, and other critical facilitieswhere it is desired to minimize disruption of operations fromnearby weak tornadoes and from strong and violent tornadosthat are on the periphery of the facility, the following arerecommended:1) For the roof deck, exterior walls, and doors, follow therecommendations given in Sections 3.4.2 and 3.4.3.2) For exterior glazing, specify laminated glass windowassemblies that are designed to resist the test Missile E loadspecified in ASTM E 1996, and are tested in accordance withASTM E 1886. Note that missile loads used for designingtornado shelters significantly exceed the missile loads usedfor designing glazing protection in hurricane-prone regions.Missiles from a strong or violent tornado passing near thefacility could penetrate the laminated glazing and result ininjury or interior damage. Therefore, to increase occupantsafety, even when laminated glass is specified, the facilityshould also incorporate a shelter as recommended above.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-129

Existing Facilities without Tornado SheltersWhere the number of recorded F3, F4, and F5 tornadoes per3,700 square miles is one or greater (see Figure 3-2 and discussionof Fujita Scale in Section 3.1.1), the best available refuge areasshould be identified if the facility does not have a tornado shelter.FEMA 431, Tornado Protection, Selecting Refuge Areas in Buildingsprovides useful information for building owners, architects, andengineers who perform evaluations of existing facilities.To minimize casualties in critical facilities, it is very important thatthe best available refuge areas be identified by a qualified architector engineer. 14 Once identified, those areas need to be clearlymarked so that occupants can reach the refuge areas withoutdelay. Building occupants should not wait for the arrival of a tornadoto try to find the best available refuge area in a particularfacility; by that time, it will be too late. If refuge areas have notbeen identified beforehand, occupants will take cover whereverthey can, frequently in very dangerous places. Corridors, as shownin Figure 3-104, sometimes provide protection, but they can alsobe death traps.Figure 3-104:View of school corridorafter passage of a violenttornado (Oklahoma,1999)14. It should be understood that the occupants of a “best available refuge area” are still vulnerable to death and injury if the refuge area was notspecifically designed as a tornado shelter.3-130 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Retrofitting a shelter space inside an existingbuilding can be very expensive. An economicalalternative is an addition that can function as fire and police stations, a designatedFor small shelters within facilities suchas a shelter as well as serve another purpose. storage room(s), office(s), or smallThis approach works well for smaller facilities. conference room(s) can be economicallyFor very large facilities, constructing two or retrofitted in accordance with FEMA 320more shelter additions should be considered to protect the occupants. Where it isin order to reduce the time it takes to reach desired to provide a large shelter area,the shelter (often there is ample warningFEMA 361 criteria are recommended.time, but sometimes an approaching tornadois not noticed until a few minutes before itstrikes). This is particularly important for hospitals and nursinghomes because of the difficulty of accommodating patients withdifferent medical needs.The recommendations given in Section 3.5 are summarized inTable 3-6.Table 3-6: Critical Facilities Located in Tornado-Prone RegionsProposed FacilityOccupant protectionRefer to FEMA 361 for design guidance.Interior non-load-bearing masonry walls See recommendations in Section 3.3.3.3.Wind-borne missilesHealthcare and other critical facilities where it is desiredto minimize disruption of operations from nearby weaktornadoesAvoid use of brick veneer, aggregate surfacing, roofpavers, slate, and tile.See recommendations in Section 3.5.Existing facilities without specifically designed tornado sheltersIf one or more F3-F5 tornadoes per 3,700 square milesIdentify best available refuge areas. See Figure 3-2 forhistorical data on frequency, and refer to FEMA 431(2003) for identification guidance.If six or more F3-F5 tornadoes per 3,700 square milesConsider incorporating a shelter within the building orinside a new building addition. Refer to FEMA 320 andFEMA 361 for design guidance.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-131

3.6 REMEDIAL WORK ON EXISTINGFACILITIESAmerican Red Cross (ARC) Publication4496, Standards for Hurricane EvacuationShelter Selection (2002) providesinformation regarding assessing existingbuildings for use as hurricane shelters.Unless a facility has been specificallydesigned for use as a shelter, it shouldonly be used as a shelter of last resort, andeven then, only if it meets the criteria givenin ARC 4496.Many existing critical facilities need to strengthen theirstructural or building envelope components. The reasonsfor this are the deterioration that has occurredover time, or inadequate facility strength to resist current designlevel winds. It is recommended that building owners havea vulnerability assessment performed by a qualified architecturaland engineering team. A vulnerability assessment should beperformed for all facilities older than 5 years. However, as illustratedby Figure 3-30 and the case of Garden Park Medical Centerdiscussed in Section 4.2, an assessment is recommended for all facilitieslocated in areas where the basic windspeed is greater than 90 mph (even if thefacility is younger than five years). It is particularlyimportant to perform vulnerabilityassessments on critical facilities located inhurricane-prone and tornado-prone regions.Components that typically make buildingsconstructed before the early 1990s vulnerableto high winds are weak non-load-bearingmasonry walls, poorly connected precast concretepanels, long-span roof structures withlimited uplift resistance (e.g., at gyms), inadequatelyconnected roof decks, weak glasscurtain walls, building envelope, and exterior-mounted equipment.Although the technical solutions to these problems are notdifficult, the cost of the remedial work is typically quite high. If3-132 MAKING CRITICAL FACILITIES SAFE FROM High Wind

funds are not available for strengthening orreplacement, it is important to minimize therisk of injury and death by evacuating areasadjacent to weak non-load-bearing walls,weak glass curtain walls, and areas belowlong-span roof structures when winds above60 mph are forecast.As a result of building code changes andheightened awareness, some of the commonbuilding vulnerabilities have generally beeneliminated for facilities constructed in themid-1990s or later. Components that typicallyremain vulnerable to high winds are thebuilding envelope and exterior-mounted mechanical,electrical, and communicationsequipment. Many failures can be averted byidentifying weaknesses and correcting them.Critical facilities sometimes occupybuildings that have changed their originaluse (see the case of Hancock County EOC,discussed in Section 4.4). Buildings thatwere not designed for a critical occupancywere likely designed with a 1.0 ratherthan a 1.15 importance factor, and henceare not as wind-resistant as needed. Itis particularly important to perform avulnerability assessment if a facilityis located in a building not originallydesigned for a critical occupancy,especially if the facility is located in ahurricane- or tornado-prone region.By performing a vulnerability assessment, items that need to bestrengthened or replaced can be identified and prioritized. A proactiveapproach in mitigating weaknesses can save significant sumsof money and decrease disruption or total breakdown in criticalfacility operations after a storm. For example,a vulnerability assessment on a school such asthat shown in Figure 3-105 can identify weaknessof exterior classroom walls. Replacingwalls before a hurricane is much cheaperthan replacing the walls and repairing consequentialdamages after a storm, and proactivework avoids the loss of use while repairs aremade.A comprehensive guide for remedial workon existing facilities is beyond the scope ofthis manual. However, the following are examplesof mitigation measures that are oftenapplicable.Before beginning remedial work, it isnecessary to understand all significantaspects of the vulnerability of a facilitywith respect to wind and wind-driven rain.If funds are not available to correct allidentified deficiencies, the work should besystematically prioritized so that the itemsof greatest need are first corrected. Forexample, at a building such as that shownin Figure 3-105, had the windows beenretrofitted with shutters, that effort wouldhave been ineffective, because the wallsthemselves collapsed. Mitigation effortscan be very ineffective if they do notaddress all items that are likely to fail.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-133

Figure 3-105:Several walls at this schoolcollapsed. Windows werelocated above a nonload-bearingmasonrywall. Hurricane Katrina(Mississippi, 2005)3.6.1 Structural SystemsAs discussed in Section 3.1.4.1, roof decks on many facilities designedprior to the 1982 edition of the SBC and UBC and the1987 edition of the NBC are very susceptible to failure. Poorly attacheddecks that are not upgraded are susceptible to blow-off, asshown in Figure 3-106. Decks constructed of cementitious woodfiber,gypsum, and lightweight insulating concrete over formboards were commonly used on buildings built in the 1950s and1960s. In that era, these types of decks typically had very limiteduplift resistance due to weak connections to the support structure.Steel deck attachment is frequently not adequate because ofan inadequate number of welds, or welds of poor quality. Olderbuildings with overhangs are particularly susceptible to blow-off, asshown in Figure 3-107, because older codes provided inadequateuplift criteria.3-134 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Figure 3-106:The school’s built-up roofblew off after one of thecementitious wood-fiberdeck panels detachedfrom the joists. HurricaneKatrina (Mississippi, 2005)Figure 3-107:The cementitious woodfiberdeck panels detachedfrom the joists along theoverhangs and causedthe school’s built-upmembranes to lift andpeel. Hurricane Katrina(Mississippi, 2005)MAKING CRITICAL FACILITIES SAFE FROM High Wind3-135

A vulnerability assessment of the roof deck should include evaluatingthe existing deck attachment, spot checking the structuralintegrity of the deck (including the underside, if possible), andevaluating the integrity of the beams/joists. If the deck attachmentis significantly overstressed under current design windconditions or the deck integrity is compromised, the deck shouldbe replaced or strengthened as needed. The evaluation should beconducted by an investigator experienced with the type of deckused on the building.If a low-slope roof is converted to a steep-slope roof, the newsupport structure should be engineered and constructed to resistthe wind loads and avoid the kind of damage shown inFigure 3-108.Figure 3-108:The school’s woodsuperstructure installedas part of a steep-slopeconversion blew awaybecause of inadequateattachment. HurricaneKatrina (Louisiana, 2005)3-136 MAKING CRITICAL FACILITIES SAFE FROM High Wind

3.6.2 Building EnvelopeThe following recommendations apply to building envelope componentsof existing critical facilities.3.6.2.1 Sectional and Rolling DoorsSectional and rolling doors (e.g., at fire station apparatus bays andhospital loading docks), installed in older buildings before attentionwas given to the wind resistance of these elements, are verysusceptible to being blown away. Although weak doors can be retrofitted,it is difficult to ensure that the door, door tracks, andconnections between the door and tracks are sufficient. It is thereforerecommended that weak doors and tracks be replaced withnew assemblies that have been tested to meet the factored designwind loads. As part of the replacement work, nailers between thetracks and building structure should either be replaced, or theirattachment should also be strengthened.If a facility has more than one sectional or rolling door, all doorsshould be replaced, rather than just replacing one of the doors.The fire station shown in Figure 3-109 had six sectional doors.One door had been replaced before a hurricane. It performedvery well, but three of the older doors were blown away and two ofthe older doors remained in place but had some wind damage.Figure 3-109:The new door in thecenter performed verywell, but the older doorson either side of it wereblown away. HurricaneCharley (Florida, 2004)MAKING CRITICAL FACILITIES SAFE FROM High Wind3-137

3.6.2.2 Windows and SkylightsWindows in older facilities may possess inadequate resistanceto wind pressure. Window failures are typically caused by windbornedebris, however, glazing or window frames may fail as aresult of wind pressure (see Figure 3-110). Failure can be causedby inadequate resistance of the glazing, inadequate anchorageof the glazing to the frame, failure of the frame itself, or inadequateattachment of the frame to the wall. For older windowsthat are too weak to resist the current design pressures, windowassembly replacement is recommended. Some older window assemblieshave sufficient strength to resist the design pressure, butare inadequate to resist wind-driven rain. If the lack of water resistanceis due to worn glazing gaskets or sealants, replacing thegaskets or sealant may be viable. In other situations, replacing theexisting assemblies with new, higher-performance assemblies maybe necessary.Figure 3-110:Wind pressure causedthe window frames onthe upper floor to fail (redarrow). Hurricane Katrina(Mississippi, 2005)It is recommended that all non-impact-resistant, exterior glazinglocated in hurricane-prone regions (with a basic wind speed of100 mph or greater) be replaced with impact-resistant glazingor be protected with shutters, as discussed in Section 3.4.3.2.3-138 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Shutters are typically a more economical approach for existingfacilities. There are a variety of shutter types, all illustrated byFigures 3-111 to 3-113. Accordion shutters are permanentlyattached to the wall (Figure 3-111). When a hurricane is forecast,the shutters are pulled together and latched into place. Panelshutters (Figure 3-112) are made of metal or polycarbonate. Whena hurricane is forecast, the shutters are taken from storage andinserted into metal tracks that are permanently mounted to thewall above and below the window frame. The panels are lockedinto the frame with wing nuts or clips. Track designs that havepermanently mounted studs for the nuts have been shown to bemore reliable than track designs using studs that slide into thetrack. A disadvantage of panel shutters is the need for storagespace. Roll-down shutters (Figure 3-113) can be motorized orpulled down manually. Figure 3-113 illustrates the benefits ofshuttering. Two of the unprotected window units experiencedglass breakage and the third window unit blew in.Figure 3-111:This school has accordionshutters. Hurricane Ivan(Florida, 2004)MAKING CRITICAL FACILITIES SAFE FROM High Wind3-139

Figure 3-112:Illustrates a metal panelshutter. Hurricane Georges(Puerto Rico, 1998)Figure 3-113:The lower windowassembly was protectedwith a motorized shutter.Hurricane Ivan (Florida,2004)Deploying accordion or panel shutters a few stories above grade isexpensive. Although motorized shutters have greater initial cost,their operational cost should be lower. Other options for providingmissile protection on upper levels include replacing the existing as-3-140 MAKING CRITICAL FACILITIES SAFE FROM High Wind

semblies with laminated glass assemblies, or installing permanentimpact resistant screens. Engineered films are also available for applicationto the interior of the glass. The film needs to be anchoredto the frame, and the frame needs to be adequately anchored tothe wall. The film degrades over time and requires replacement(approximately every decade). Use of laminated glass or shutters isrecommended in lieu of engineered films.3.6.2.3 Roof CoveringsFor roofs with weak metal edge flashing or coping attachment,face-attachment of the edge flashing/coping (as shown in Figure3-63) is a cost-effective approach to greatly improve the wind resistanceof the roof system.The vulnerability assessment of roofs ballasted with aggregate,pavers, or cementitious-coated insulation boards, should determinewhether the ballast complies with ASNI/SPRI RP-4.Corrective action is recommended for non-compliant, roof coverings.It is recommended that roof coverings with aggregatesurfacing, lightweight pavers, or cementitious-coated insulationboards on buildings located in hurricane-prone regions be replacedto avoid blow off (see Figure 3-114).Figure 3-114:Aggregate from thehospital’s built-up roofsbroke several windowsin the intensive care unit,which had to be evacuatedduring the hurricane.Hurricane Charley(Florida, 2004)MAKING CRITICAL FACILITIES SAFE FROM High Wind3-141

When planning the replacement of a roof covering, it is recommendedthat all existing roof covering be removed down to thedeck rather than simply re-covering the roof. Tearing off the coveringprovides an opportunity to evaluate the structural integrityof the deck and correct deck attachment and other problems. Forexample, if a roof deck was deteriorated due to roof leakage (seeFigure 3-115), the deterioration would likely not be identified ifthe roof was simply re-covered. By tearing off down to the deck,deteriorated decking like that shown in Figure 3-115 can be foundand replaced. In addition, it is recommended that the attachmentof the wood nailers at the top of parapets and roof edges beevaluated and strengthened where needed, to avoid blow-off andprogressive lifting and peeling of the new roof membrane (seeFigure 3-116).Figure 3-115:The built-up roof on thisschool was blown off aftera few of the rotted woodplanks detached from thejoists. Hurricane Katrina(Mississippi, 2005)3-142 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Figure 3-116:The edge nailer on topof an old brick wall at ahospital blew off because itwas inadequately attached.Hurricane Ivan (Florida,2004)If the roof has a parapet, it is recommended that the inside of theparapet be properly prepared to receive the new base flashing. Inmany instances, it is prudent to re-skin the parapet with sheathingto provide a suitable substrate. Base flashing should not be applieddirectly to brick parapets because they have irregular surfaces thatinhibit good bonding of the base flashing to the brick (see Figure3-117). Also, if moisture drives into the wall from the exteriorside of the parapet with base flashing attached directly to brick,the base flashing can inhibit drying of the wall. Therefore, ratherthan totally sealing the parapet with membrane base flashing, theupper portion of the brick can be protected by metal panels (asshown in Figure 3-93), which permit drying of the brick.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-143

Figure 3-117:Failed base flashingadhered directly to thebrick parapet. HurricaneKatrina (Louisiana, 2005)3.6.3 Exterior-Mounted EquipmentFastening rooftop equipment to curbs,as discussed in Section 3.3.4.1, is acost-effective approach to minimize windinducedproblems.Exterior-mounted equipment on existingcritical facilities should be carefully examinedand evaluated.3.6.3.1 Antenna (Communications Mast)Antenna collapse is very common. Besides loss of communications,collapsed masts can puncture roof membranes or causeother building damage as shown in Figure 3-118. This case alsodemonstrates the benefits of a high parapet. Although the roofstill experienced high winds that blew off this penthouse door, theparapet prevented the door from blowing off the roof.In hurricane-prone regions, it is recommended that antennaestrength be evaluated as part of the vulnerability assessment.Chapter 15 of ANSI/TIA-222-G provides guidance on the structuralevaluation of existing towers. Appendix J of that standardcontains checklists for maintenance and condition assessments.Additional bracing, guy-wires, or tower strengthening or replacementmay be needed.3-144 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Figure 3-118:The antenna at thishospital collapsed andwas whipped back andforth across the roofmembrane. HurricaneAndrew (Florida, 1992)3.6.3.2 Lightning Protection SystemsAdhesively-attached conductor connectors and pronged spliceconnectors typically have not provided reliable attachment duringhurricanes. To provide more reliable attachment for LPS locatedin hurricane-prone regions where the basic wind speed is 100 mphor greater, or on critical facilities in excess of 100 feet above grade,it is recommended that attachment modifications based on theguidance given in Section 3.3.4.3 be used.The recommendations given in Section 3.6 are summarized inTable 3-7.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-145

Table 3-7: Recommendations for Remedial Work on Existing Critical FacilitiesWeaknessCritical facilities older than 5 years, or any age iflocated in an area with basic wind speed greater than90 mph.A building with weak non-load-bearing masonry orcurtain walls, poorly connected precast concrete panels,or weak long-span roof structures.Sectional and rolling doors.Worn window gaskets and sealants.Buildings in a hurricane-prone region where the basicwind speed is 100 mph or greater, with non-impactresistantexterior glazing.Recommended remedyPerform vulnerability assessment with life-safety issues asthe first priority, and property damage and interruption ofservice as the second priority.Implement remedial work on elements with insufficientstrength to resist wind loads if the facility will be occupiedduring high wind events (e.g., strong thunderstorms).Replace weak doors and tracks.Replace with new gaskets and sealants, or replace windowassembly.Replace with impact-resistant glazing or protect withshutters.Inadequately attached edge flashings or copings. Face-attach the vertical flanges. See Figure 3-63.Ballasted single-ply roof membranes.Buildings in a hurricane-prone region with aggregateroof surfacing, lightweight pavers, or cementitiouscoatedinsulation boards.Rooftop equipment unanchored or poorly anchored.Weak roof deck connections or weak roof structure.Emergency generators in a hurricane-prone region notadequately protected from wind-borne debris.Antennae (communication masts) in hurricane-proneregions.Lightning protection systems with adhesively-attachedconductor connectors or pronged splice connectorslocated in hurricane-prone regions where the basic windspeed is 100 mph or greater, or on critical facilities inexcess of 100 feet above grade.Take corrective action if non-compliant with ANSI/SPRI RP-4.Replace roof covering to avoid blow-off.Add screws or bolts to anchor equipment to curbs. Addcables to secure fan cowlings. Add latches to secureequipment access panels. See Section 3.3.4.1.When planning replacement of roof covering, remove roofcovering and strengthen attachment of deck and/or roofstructure. See Section 3.6.2.3.Build an enclosure to provide debris protection. SeeSection 3.4.5.1.Evaluate wind resistance and strengthen as needed. SeeChapter 15 and Appendix J of ANSI/TIA-222-G.Modify attachment according to recommendations inSection 3.4.4.3.3-146 MAKING CRITICAL FACILITIES SAFE FROM High Wind

3.7 Checklist for BuildingVulnerability of CriticalFacilities Exposed to HighWindsThe Building Vulnerability Assessment Checklist (Table 3-8)is a tool that can help in assessing the vulnerability of variousbuilding components during the preliminary designof a new building, or the rehabilitation of an existing building.In addition to examining design issues that affect vulnerability tohigh winds, the checklist also examines the potential adverse effectson the functionality of the critical and emergency systemsupon which most critical facilities depend. The checklist is organizedinto separate sections, so that each section can be assignedto a subject expert for greater accuracy of the examination. Theresults should be integrated into a master vulnerability assessmentto guide the design process and the choice of appropriate mitigationmeasures.Table 3-8: Checklist for Building Vulnerability of Critical Facilities Exposed to High WindsGeneralVulnerability Sections Guidance ObservationsWhat is the age of the facility, andwhat building code and edition wasused for the design of the building?Substantial wind load improvements were madeto the model building codes in the 1980s. Manybuildings constructed prior to these improvementshave structural vulnerabilities. Since the 1990s,several additional changes have been made, themajority of which pertain to the building envelope.Older buildings, not designed and constructed inaccordance with the practices developed sincethe early 1990s, are generally more susceptible todamage than newer buildings.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-147

Table 3-8: Checklist for Building Vulnerability of Critical Facilities Exposed to High Winds (continued)Vulnerability Sections Guidance ObservationsGeneral (continued)Is the critical facility older than 5years, or is it located in a zone withbasic wind speed greater than 90mph?In either case, perform a vulnerabilityassessment with life-safety issues as the firstpriority, and property damage and interruptionof service as the second priority.SiteWhat is the design wind speed at thesite? Are there topographic featuresthat will result in wind speed-up?What is the wind exposure on site?Are there trees or towers on site?Road accessIs the site in a hurricane-proneregion?If in a hurricane-prone region, arethere aggregate surfaced roofs within1,500 feet of the facility?ASCE 7 and Section 3.1.3.Avoid selecting sites in Exposure D, and avoidescarpments and hills (Section 3.1.3).Avoid trees and towers near the facility (Section3.3.1.1). If the site is in a hurricane-proneregion, avoid trees and towers near primaryaccess roads (Section 3.4.1).Provide two separate means of access (Section3.3.1.1).ASCE 7. If yes, follow hurricane-resistant designguidance (Section 3.4).Remove aggregate from existing roofs (Section3.6.2.3). If the buildings with aggregate areowned by other parties, attempt to negotiatethe removal of the aggregate (e.g., consideroffering to pay the reroofing costs).ArchitecturalWill the facility be used as a shelter? If yes, refer to FEMA 361.Are there interior non-load-bearingwalls?Are there multiple buildings on site ina hurricane-prone region?Are multiple elevators needed for thebuilding?Design for wind load according to Section3.3.3.3.Provide enclosed walkways between buildingsthat will be occupied during a hurricane(Section 3.4.1).Place elevators in separate locations served byseparate penthouses (Section 3.4.4.1).3-148 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Table 3-8: Checklist for Building Vulnerability of Critical Facilities Exposed to High Winds (continued)Vulnerability Sections Guidance ObservationsStructural Systems Section 3.3.2Is a pre-engineered building beingconsidered?Is precast concrete being considered?Are exterior load-bearing walls beingconsidered?If yes, ensure the structure is not vulnerableto progressive collapse. If a pre-engineeredbuilding exists, evaluate to determine if it isvulnerable to progressive collapse.If yes, design the connections to resist windloads. If precast concrete elements exist, verifythat the connections are adequate to resist thewind loads.If yes, design as MWFRS and C&C.Is an FM Global-rated roof assemblyspecified?Is there a covered walkway orcanopy?Is the site in a hurricane-proneregion?Is the site in a tornado-prone region?Do portions of the existing facilityhave long-span roof structures (e.g.,a gymnasium)?Is there adequate uplift resistanceof the existing roof deck and decksupport structure?If yes, comply with FM Global deck criteria.If yes, use “free roof” pressure coefficientsfrom ASCE 7.Canopy decks and canopyframing members on older buildings often haveinadequate wind resistance. Wind-borne debrisfrom canopies can damage adjacent buildingsand cause injury.A reinforced cast-in-place concrete structuralsystem, and reinforced concrete or fully groutedand reinforced CMU walls, are recommended(Section 3.4.2).If yes, provide occupant protection. See FEMA361.Evaluate structural strength, since olderlong-span structures often have limited upliftresistance.The 1979 (and earlier) SBC and UBC,and 1984 (and earlier) BOCA/NBC, didnot prescribe increased wind loads at roofperimeters and corners. Decks (except cast-inplaceconcrete) and deck support structuresdesigned in accordance with these older codesare quite vulnerable.The strengthening of thedeck attachment and deck support structure isrecommended for older buildings.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-149

Table 3-8: Checklist for Building Vulnerability of Critical Facilities Exposed to High Winds (continued)Vulnerability Sections Guidance ObservationsStructural SystemsAre there existing roof overhangsthat cantilever more than 2 feet?Section 3.3.2 (continued)Overhangs on older buildings often haveinadequate uplift resistance.Building Envelope Section 3.3.3Exterior doors, walls, roof systems,windows, and skylights.Are soffits considered for thebuilding?Are there elevator penthouses onthe roof?Is a low-slope roof considered on asite in a hurricane-prone region?Is an EOC, healthcare facility, shelter,or other particularly important criticalfacility in a hurricane-prone region?Is the site in a tornado-prone region?Are there existing sectional or rollingdoors?Does the existing building have largewindows or curtain walls?Does the existing building haveexterior glazing (windows, glazeddoors, or skylights)?Select materials and systems, and detail to resistwind and wind-driven rain (Sections 3.3.3.1 to3.3.3.4).Design to resist wind and wind-driven waterinfiltration (Section 3.3.3.3). If there are existingsoffits, evaluate their wind and wind-driven rainresistance. If the soffit is the only element preventingwind-driven rain from being blown intoan attic space, consider strengthening the soffit.Design to prevent water infiltration at walls,roof, and mechanical penetrations (Sections3.3.3.3, 3.3.3.4, 3.3.4.1, and 3.4.4.1).A minimum 3-foot parapet is recommended onlow-slope roofs (Section 3.4.3.4).If yes, a very robust building envelope, resistantto missile impact, is recommended(Section 3.4).To minimize generation of wind-borne missiles,avoid the use of brick veneer, aggregate roofsurfacing, roof pavers, slate, and tile(Section 3.5).Older doors often lack sufficient windresistance. Either strengthen or replace. This isparticularly important for fire station apparatusbay doors.If an older building, evaluate their windresistance.If the building is in a hurricane-prone region,replace with impact-resistant glazing, or protectwith shutters.3-150 MAKING CRITICAL FACILITIES SAFE FROM High Wind

Table 3-8: Checklist for Building Vulnerability of Critical Facilities Exposed to High Winds (continued)Vulnerability Sections Guidance ObservationsBuilding EnvelopeDoes the existing building haveoperable windows?Are there existing exterior non-loadbearingmasonry walls?Are there existing brick veneer, EIFS,or stucco exterior coverings?Are existing exterior walls resistant towind-borne debris?Are there existing ballasted single-plyroof membranes?Does the existing roof haveaggregate surfacing, lightweightpavers, or cementitious-coatedinsulation boards?Does the existing roof have edgeflashing or coping?Does the existing roof systemincorporate a secondary membrane?Does the existing building have a brittleroof covering, such as slate or tile?Section 3.3.3 (continued)If an older building, evaluate its wind-drivenrain resistance.If the building is in a hurricane- or tornadoproneregion, strengthen or replace.If the building is in a hurricane-prone region,evaluate attachments. To evaluate windresistance of EIFS, see ASTM E 2359 (2006).If the building is in a hurricane-prone region,consider enhancing debris resistance, particularlyif dealing with an important critical facility.Determine if they are in compliance with ANSI/SPRI RP-4. If non-compliant, take corrective action.If the building is in a hurricane- prone region,replace the roof covering to avoid blow-off.Evaluate the adequacy of the attachment.If not, and if the building is in a hurricane-proneregion, reroof and incorporate a secondarymembrane into the new system.If the building is in a hurricane-prone region,consider replacing with a non-brittle covering,particularly if it is an important critical facility.Exterior-Mounted Mechanical EquipmentIs there mechanical equipmentmounted outside at grade or theroof?Are there penetrations through theroof?Is the site in a hurricane-proneregion?Anchor the equipment to resist wind loads (Section3.3.4.1). If there is existing equipment,evaluate the adequacy of the attachment, includingattachment of cowlings and access panels.Design intakes and exhausts to avoid waterleakage (Section 3.3.4.1).If yes, place the equipment in a penthouse, ratherthan exposed on the roof (Section 3.4.4.2).MAKING CRITICAL FACILITIES SAFE FROM High Wind3-151

Table 3-8: Checklist for Building Vulnerability of Critical Facilities Exposed to High Winds (continued)Vulnerability Sections Guidance ObservationsExterior-mounted Electrical and Communications EquipmentAre there antennae (communicationmasts) or satellite dishes?Does the building have a lightningprotection system?See Section 3.3.4.2. If there are existingantennae or satellite dishes and the building islocated in a hurricane-prone region, evaluatewind resistance. For antennae evaluation, seeChapter 15 of ANSI/TIA-222-G-2005.See Sections 3.3.4.2 and 3.4.4.3 for lightningprotection system attachment. For existinglightning protection systems, evaluate windresistance (Section 3.6.3.1)Municipal UtilitiesIs the site in a hurricane-proneregion?Is the emergency generator(s)housed in a wind- and debrisresistantenclosure?Is the emergency generator’s walllouver protected from wind-bornedebris?Is the site in a hurricane-proneregion?See Section 3.4.5.1 for emergency and standbypower recommendations.If not, build an enclosure to provide debrisprotection in a hurricane-prone region (Section3.4.5.1).If the building is in a hurricane-prone region,install louver debris impact protection (Section3.4.5.1).If yes, an independent water supply andalternative means of sewer service arerecommended, independent of municipalservices (Sections 3.4.5.2 and 3.4.5.3).3-152 MAKING CRITICAL FACILITIES SAFE FROM High Wind

3.8 References and Sources ofAdditional InformationNOTE: FEMA publications may be obtained at no cost bycalling (800) 480-2520, faxing a request to (301) 497-6378, or downloading from the library/publicationssection online at http://www.fema.gov.American Association of State Highway and TransportationOfficials, Standard Specifications for Structural Supports forHighway Signs, Luminaires and Traffic Signals, LTS-4-M and LTS-4-12, January 2001 and October 2003.American Concrete Institute, Building Code Requirements for MasonryStructures, ACI 530/ASCE 5/TMS 402, November 1996.American Institute of Architects, Buildings at Risk: Wind DesignBasics for Practicing Architects, 1997.American National Standards Institute/SPRI RP-4, Wind DesignStandard for Ballasted Single-Ply Roofing Systems, 2002.American National Standards Institute/SPRI ES-1, Wind DesignStandard for Edge Systems Used in Low Slope Roofing Systems, 2003.American National Standards Institute/TelecommunicationsIndustry Association, Structural Standards for Antenna SupportingStructures and Antennas, ANSI/TIA-222-G, August 2005.American Red Cross, Standards for Hurricane Evacuation ShelterSelection, Publication 4496, July 1992, rev. January 2002.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-153

American Society of Civil Engineers, Structural Engineering Institute,Minimum Design Loads for Buildings and Other Structures,ASCE/SEI 7-05, Reston, VA, 2005.American Society for Testing and Materials, Standard TestMethod for Field Determination of Water Penetration of InstalledExterior Windows, Skylights, Doors, and Curtain Walls by Uniform orCyclic Static Air Pressure Difference, ASTM E1105, 2000.American Society for Testing and Materials, Standard TestMethod for Structural Performance of Sheet Metal Roof and SidingSystems by Uniform Static Air Pressure Difference, ASTM E1592,2000.American Society for Testing and Materials, Standard TestMethod for Structural Performance of Exterior Windows, CurtainWalls, and Doors by Cyclic Static Air Pressure Differential, ASTME1233, December 2000.American Society for Testing and Materials, Standard Practicefor Installation of Exterior Windows, Doors and Skylights, ASTME2112, 2001.American Society for Testing and Materials, Standard TestMethod for Performance of Exterior Windows, Curtain Walls, Doors,and Impact Protective Systems Impacted by Missile(s) and Exposed toCyclic Pressure Differentials, ASTM E1886, 2005.American Society for Testing and Materials, StandardSpecification for Performance of Exterior Windows, Curtain Walls,Doors and Impact Protective Systems Impacted by Windborne Debris inHurricanes, ASTM E1996, 2005.American Society for Testing and Materials, StandardSpecification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware,ASTM A153, April 2005.American Society for Testing and Materials, StandardSpecification for Steel, Sheet, Cold-Rolled, Carbon, Structural,High-Strength Low-Alloy, High-Strength Low-Alloy with ImprovedFormability, Solution Hardened, and Bake Hardenable, ASTMA1008/A1008M, 2006.3-154 MAKING CRITICAL FACILITIES SAFE FROM High Wind

American Society for Testing and Materials, Test Method for FieldPull Testing of an In-Place Exterior Insulation and Finish SystemClad Wall Assembly, ASTM E 2359, 2006.American Society for Testing and Materials, Standard TestMethod for Structural Performance of Exterior Windows, Doors,Skylights, and Curtain Walls by Cyclic Air Pressure Differential,ASTM E1233, 2006.American Society of Heating, Refrigeration and Air-Conditioning Engineers, Inc. (ASHRAE), Ventilation forAcceptable Indoor Air Quality, Standard 62.1, 2004.American Society of Heating, Refrigeration and Air-Conditioning Engineers, Inc. (ASHRAE), Standard 62.1 User’sManual, 2006.Brick Industry Association, Anchored Brick Veneer-Wood FrameConstruction, Technical Notes 28, Revised August 2002.Brick Industry Association, Wall Ties for Brick Masonry,Technical Notes 44B, Revised May 2003.Brick Industry Association, Brick Veneer/Steel Stud Walls,Technical Notes 28B, December 2005.Door & Access Systems Manufacturers Association, ConnectingGarage Door Jambs to Building Framing, Technical Data Sheet#161, December 2003.FM Global, Loss Prevention Data for Roofing Contractors,Norwood, MA, dates vary.Factory Mutual Research, Approval Guide, Norwood, MA,updated quarterly.FEMA, Building Performance: Hurricane Andrew in Florida, FEMAFIA-22, Washington, DC, December 1992.FEMA, Building Performance: Hurricane Iniki in Hawaii, FEMAFIA-23, Washington, DC, January 1993.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-155

FEMA, Corrosion Protection for Metal Connectors in Coastal Areas,FEMA Technical Bulletin 8-96, Washington, DC, August 1996.FEMA, Typhoon Paka: Observations and Recommendations onBuilding Performance and Electrical Power Distribution System,FEMA-1193-DR-GU, Washington, DC, March 1998.FEMA, Hurricane Georges in Puerto Rico, FEMA 339, Washington,DC, March 1999.FEMA, Oklahoma and Kansas Midwest Tornadoes of May 3, 1999,FEMA 342, Washington, DC, October 1999.FEMA, Coastal Construction Manual, Third Edition, FEMA 55,Washington, DC, 2000.FEMA, Design and Construction Guidance for Community Shelters,FEMA 361, Washington, DC, July 2000.FEMA, Installing Seismic Restraints for Mechanical Equipment,FEMA 412, Washington, DC, December 2002.FEMA, Tornado Protection, Selecting Safe Areas in Buildings,FEMA 431, Washington, DC, October 2003.FEMA, Installing Seismic Restraints for Electrical Equipment,FEMA 413, Washington, DC, January 2004.FEMA, Installing Seismic Restraints for Duct and Pipe, FEMA 414,Washington, DC, January 2004.FEMA, Taking Shelter From the Storm: Building a Safe Room InsideYour House, FEMA 320, Washington, DC, March 2004.FEMA, MAT Report: Hurricane Charley in Florida, FEMA 488,Washington, DC, April 2005.FEMA, MAT Report: Hurricane Ivan in Alabama and Florida,FEMA 489, Washington, DC, August 2005.FEMA, Home Builder’s Guide to Coastal Construction Technical FactSheet Series, FEMA 499, August 2005.3-156 MAKING CRITICAL FACILITIES SAFE FROM High Wind

FEMA, Attachment of Brick Veneer in High-Wind Regions—Hurricane Katrina Recovery Advisory, Washington, DC, December2005.FEMA, MAT Report: Hurricane Katrina in the Gulf Coast, FEMA549, Washington, DC, July 2006.FEMA, Attachment of Rooftop Equipment in High-Wind Regions—Hurricane Katrina Recovery Advisory, Washington, DC, May 2006,rev. July 2006.FEMA, Rooftop Attachment of Lighting Protection Systems in High-Wind Regions—Hurricane Katrina Recovery Advisory, Washington,DC, May 2006, rev. July 2006.Institute of Electrical and Electronics Engineers, Inc., NationalElectrical Safety Code, ANSI/IEE/C2, 2006.International Code Council, 2006 International Building Code,ICC IBC-2006, March 2006.McDonald, J.R. and Lea, P.A, A Study of Building Damage Causedby Wind Forces, Institute for Disaster Research, Texas TechUniversity, 1978.National Institute of Building Sciences, Building Envelope DesignGuide, Available online at www.wbdg.org/design/envelope.php.National Research Council of Canada, Institute for Researchin Construction, Wind Design Guide for Mechanically AttachedFlexible Membrane Roofs, B1049, 2005.Reinhold, Timothy A. “Calculating Wind Loads and AnchorageRequirements for Rooftop Equipment,” American Society ofHeating, Refrigerating and Air-Conditioning Engineers Journal,Volume 48, Number 3, March 2006.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-157

OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES 44.1 INTRODUCTIONThis chapter presents some observations on the performanceof critical facilities during Hurricane Katrina that identifythe various ways in which building and equipment damage,as well as loss of municipal services, can disrupt facility operations.These observations are intended to help people who own, operate,design, and build critical facilities to adjust their buildingdesigns, construction, and facility management practices to reflectthe needs of comprehensive risk reduction.During Hurricane Katrina, surging floodwaters and high windscaused considerable and often catastrophic building damage,forcing many critical facilities to cease operations and evacuatetheir premises even before the storm had passed. In many instancesthe continued operation of hospitals, police and firestations, schools, and EOCs was severely compromised by relativelyminor damage to the building or building-mounted equipment.Although the structural components of most critical facilities survivedthe hurricane, other building components performed lesswell, causing serious disruptions.The observations highlighted in this chapter, made by a team ofbuilding professionals (architects and engineers) experiencedin hazard mitigation, document the variety and severity of thebuilding damage, and the corresponding effects on facility operations.Field inspections and discussions with facility managers andother personnel served as the basis for analysis of the experiencesof individual facilities. The descriptions of these experiences areOBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-1

accompanied with suggestions on possible mitigation measuresthat would improve hazard-resistance and protect the facility’sfunctionality in the future. A comprehensive risk assessment of thefacility’s operation and building components and systems wouldbe required before any specific mitigation measures were implemented.This chapter emphasizes the experiences and lessonslearned from facility operation disruptions in particular circumstances,and may not be applicable to all situations.4-2 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

4.2 HEALTH CARE FACILITIES4.2.1 BACKGROUNDHealth care facilities are at the front line of communityprotection, especially during and after a natural disasterevent. Their capacity to continue to provide services to existingpatients, and to respond to the needs of victims following adisaster, depends not only on protecting the integrity of the structureand the building envelope, but on the facilities’ ability tocarry out their intended functions with little or no interruption.Continued and uninterrupted operation of health care facilities,regardless of the nature of the disaster, is one of the most importantelements of a natural disaster safety program.Health care facilities, especially hospitals, are usually very complexbuilding systems, because they accommodate diverse and highlyspecialized services in a strictly controlled environment. Hospitalbuildings must be designed to provide appropriate spatial arrangementfor the flawless interaction between staff, patients, andvisitors. They also require a complex network of technological infrastructureto support the hospital’s functions. Even the smallestbreakdown in this complex network can cascade into a serious disruptionof operations.Protecting the functionality of a hospital requires very careful facilityplanning and design that is in accordance with the moststringent flooding and high-wind mitigation requirements applicableto the site. The damage sustained by hospitals duringOBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-3

Hurricane Katrina emphasized the fact that many of the Nation’shospitals occupy old or inadequate buildings that may not be sufficientlyprotected against hazards. In particular, some of thehospitals were planned and built before mitigation against naturalhazards became common practice.Considering the expanding gap between the functionality ofaging hospitals on the one side, and the requirements of newtechnologies and the needs of a growing and aging populationon the other, it is expected that many of the country’s hospitalswill have to be replaced, upgraded, or rebuilt in the coming years.Some medical industry forecasts predict that by the end of the decadethe United States will spend $20 billion annually for thispurpose. Since new or rebuilt hospitals will have to last for a longtime, the anticipated construction program provides an opportunityto rethink hospital planning and design, and to consider howto avoid hazard areas and reduce the vulnerability with improvedhospital design.The following observations are based on published sources at thetime of Hurricane Katrina, and on the subsequent interviews withproviders and regulators in both Louisiana and Mississippi. Thedamage assessments present a picture of common effects on themedical facilities, which are consistent across the region affectedby Hurricane Katrina. Generous contributions by the following institutionsand their staff are acknowledged:m St. Tammany Parish Office of Homeland Security andEmergency Preparedness (Covington, Louisiana)m Touro Infirmary (New Orleans, Louisiana)m West Jefferson Medical Center (Jefferson Parish, Louisiana)m Hancock Medical Center (Bay St. Louis, Mississippi)m Garden Park Medical Center (Gulfport, Mississippi)m Guest House of Slidell (Slidell, Louisiana)m Slidell Memorial Hospital (Slidell, Louisiana)4-4 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

m LSU Health Sciences Center (New Orleans, Louisiana)m Charity Hospital (New Orleans, Louisiana)m University Hospital (New Orleans, Louisiana)4.2.2 Effects of FloodingThe damage caused by Hurricane Katrina flooding was significantlymore serious than the damage caused by wind. Along theGulf Coast, the storm surge was higher than previously experienced,which caught many health care providers by surprise (seeFigure 1-2). In most places, the storm surge flooding receded inseveral hours, but in New Orleans the floodwaters remained formore than a week. Apart from the damage and disruption causedby floodwaters that penetrated the facilities’ lower levels, manyhospitals in New Orleans were completely surrounded by floodwaters,which cut off all surface access.As a result of the disrupted access, most hospitals had to manageon their own, without any assistance from the outside. Patientsand visitors were stranded, along with staff that could not be relievedfor days. The injured, and others in need of emergencycare, could not be brought in for treatment. Family and friendsof people stranded in the hospitals had no way of communicatingwith them. Food, water, medical, and other supplies could not bebrought in except by small boats and helicopters, or in some instances,by military vehicles. The evacuation of the critically illpatients, and eventually others, was possible only by boat or by helicopter.Hospitals with dedicated or improvised elevated helipadsmanaged the evacuation much better than others.Hospitals and nursing homes that were inundated during Katrinaexperienced the greatest damage. Hospital functions located inthe areas exposed to floodwaters had to be shut down. In manycases, the elevators and other mechanical and electrical serviceswere shut down by the floodwaters.Flooding caused considerable disruption of utility services in mosthospitals in the New Orleans area. Sewers flooded or pumpingstations shorted out, disabling sewage and liquid waste disposal.OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-5

The water supply was interrupted and, in many instances, onsitesources were contaminated and could not be used for drinkingpurposes. Emergency generators and electrical switchgear equipment,as well as underground transformers flooded and were putout of commission.In several instances, communications panels and other controlswere located on the first floor and shorted out. The heat and thebuildup of humidity in New Orleans ruined the telephone connectionsand the fire alarm systems in some hospitals, even thoughfloodwaters did not contact sensitive communications equipmentdirectly.4.2.3 Effects of High WindsIn general, three types of wind damage affected the hospitals:damaged roof coverings, rooftop equipment, and windowbreakage. Damaged roof coverings that were either peeled off orpunctured by wind-borne debris exposed the interior to rainwaterpenetration and additional damage. Similarly, rooftop equipmentdisplaced by wind left unprotected roof openings exposedto rainwater penetration. Water damage ranged from saturation ofinterior surfaces, like walls and ceilings, to ruined equipment andconsiderable mold growth.Window breakage during the storm was particularly dangerous,because it allowed the penetration of rainwater, and wind that cancause pressurization in the interior. Hospital patient rooms, however,faced the greatest risks from window breakage, because manyof their occupants could not be moved away from monitors, medicalgases, and other equipment.4.2.4 Site DesignAlthough most of New Orleans is located in the lowlands that areprotected by a system of canals and levees, the hospitals were notbuilt to resist the flooding caused by levee failures. As a result ofHurricane Katrina and the failure of levees, only 3 out of morethan 20 of the city’s hospitals remained open during the storm(see Figure 4-1). Only one of these, the Touro Infirmary, was not4-6 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

completely surrounded by water, retaining access on one side. Accessproblems affected all hospitals. West Jefferson Medical Centerhad planned to deploy their staff in two shifts, to allow the secondshift to stay at home until the storm had passed and then come torelieve the staff locked down in the hospital. Because of impededaccess, the relief staff could not get to the hospital, which put anadded burden on the initial staff, already nearing exhaustion.Figure 4-1:University Hospitalsurrounded by 4 feet ofwaterFigure 4-2: Evacuation of NewOrleans by helicopterOBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-7

Hancock Medical Center in Bay St. Louis, Mississippi, although locatedoutside of the 500-year floodplain, experienced 3-foot deepflooding as a result of the storm surge (see Figure 4-3). Accessto the hospital was disrupted long before Katrina made landfallbecause, prior to the storm arrival, there was a 33-mile traffic backupon the road leading out of town. Access was important becauseall the functioning hospitals needed relief supplies, medical gases,water, and fuel for their emergency generators. In many cases, theonly way to resupply the facilities was by air, using large Chinookhelicopters. These helicopters are too heavy for most roof structures,and to use them for emergencies in the future, a secondhelipad may be necessary on the site, requiring sufficient glide anglesfor landing and takeoff of the largest aircraft.Access to emergency services was also blocked by the water and,in some cases, by trees and utility lines that were knocked down.Once the hospitals had access restored, they were deluged bythe injured from nearby communities. Slidell Memorial Hospitaladministered 40,000 tetanus shots in the days after the storm.Hancock Medical Center saw 600 to 700 patients a day for up to 2weeks after the surge water receded.Figure 4-3:The lobby of HancockMedical Center was under3 feet of water.4-8 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

Perhaps the most serious consequence of the impeded access wasthe way it affected the evacuation of hospitals in New Orleans.Serious disruptions in hospital operations required immediateevacuation, which could not take place because the streets werenot accessible for up to 5 days. There was a critical need for ahelipad, either on the roof or an equivalent landing area on aparking structure, with emergency lighting for night operation.Elevated parking structures were a great asset, providing both aprotection for the vehicles and a convenient helicopter landingsite on the roof. They were especially useful if the parking structurehad an elevated pedestrian bridge to the hospital.4.2.5 Architectural DesignA typical hospital configuration is based on access requirementsthat usually place the emergency department on the first floorin order to receive walk-in patients or those brought in by ambulances.Clinical laboratory and imaging are frequently on thefirst floor as well, as are surgery and intensive care units in manysmaller hospitals. All of these are vital services in the event of anemergency and for providing routine patient care. Location onthe first floor frequently exposes them to additional risks fromnatural hazards, especially flooding, as became evident duringHurricane Katrina.Building configuration and general shape frequently contribute tohigh-wind damage. Protrusions and projections in walls and roofscause additional wind turbulence that increases uplift pressures.The penthouse at West Jefferson Medical Center illustrates thevulnerability of projections and corners to high winds (see Figure4-4). Large portions of metal cladding came loose because theywere not designed or constructed to resist these loads.Canopies, which most hospitals have over drop-off areas, are particularlysusceptible to uplift and other damage, if not designed toresist the loads (see Figure 4-5). Glass-enclosed lobbies and atria,common to many hospitals, also proved to be a hazard, becauseof the large areas of usually unprotected glazing that could easilyshatter under the impact of wind-borne debris. In many cases,these areas were closed during the storm, thereby cutting off amajor point of access to the hospitals.OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-9

Figure 4-4:Penthouse at the WestJefferson Medical CenterFigure 4-5:Canopy soffit damage atWest Jefferson MedicalCenterAt Louisiana State University Hospital, the emergency generatorsin the basement were flooded and shut down, which put theentire hospital out of commission. Similarly, all the major mechanicalequipment in Charity Hospital in New Orleans was in thebasement, including fifteen 5,000-watt emergency generators. Thehospital had to be evacuated soon after the basement flooded andthe emergency power supply failed. Touro Infirmary, however, hadthe emergency power generators located on the third floor. Thisallowed them to run most of the critical systems, including the4-10 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

air conditioning, without interruption until the generators brokedown from prolonged use and contaminated fuel supplies.Critical operations such as emergency and surgical departments,recovery rooms, ICUs, and other patient bed units and laboratoriesshould not be located in areas below ground or below theelevation of possible flooding and storm surge. These criticalfunctions should be located on upper floors or in areas wherecommunication between floors is easily accomplished. These areasshould have no windows, or should have protected glazing to preventwindow breakage and rain water penetration.4.2.6 Building EnvelopeBuilding envelope damage during Hurricane Katrina was widespreadand included uplifted roof coverings and flashing, roofingpunctured by flying debris or overturned roof-mounted equipmentthat led to extensive rainwater penetration, wall claddingseparation, and window and door breakage.The building envelope on the Garden Park Medical Center inGulfport, a relatively new building opened in 2000, sustained considerabledamage from 130-mph winds during Hurricane Katrina.The estimated wind speed may appear to have been close to thecurrent design wind speed of 135 mph for this facility, but the actualpressures were below the current design pressures as a resultof the 1.15 importance factor required for hospitals. Wall claddingconsisting of EIFS was blown off in several areas, allowingwater to penetrate wall cavities (see Figure 4-6). Extensive use ofEIFS, despite a long track record of failure during hurricanes,contributed to significant damage from water penetration. EIFS isa popular wall cladding system, but not strong enough to preventdamage from wind-borne debris in cases where EIFS is appliedover studs. In addition, EIFS design or construction deficienciesfrequently make it insufficiently resistant to suction pressurescaused by high winds. This is especially significant for hospitals,where such damage can allow water penetration and trigger seriousdisruptions in the mechanical and electrical systems anddamage the building interior. Hospitals in hurricane-prone regionsthat have EIFS should have field testing performed toevaluate its attachment.OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-11

Figure 4-6:Repair of EIFS wallcovering on Garden ParkMedical CenterHancock Medical Center suffered damage to the wall sheathingbehind the exterior brick veneer. This damage resulted fromstanding water at significant depths in various locations aroundthe building. The sheathing retained moisture long enough tocompromise its integrity through swelling, and to support thegrowth of mold and bacteria. There have been numerous examplesof the failure of brick veneer. The reasons for this includecorroded brick metal ties, insufficient number of metal ties installed,or ties not adequately embedded in the mortar.Many hospitals have low-slope roofs. There have been many instancesof failure of this type of roof, frequently beginning atthe edge flashing and progressively spreading to other parts ofthe roof. Roofs are also susceptible to puncture, as happened atthe Hancock Medical Center and Garden Park Medical Center(see Figure 4-7). Rubber walkway pads were blown away and theroof membrane was punctured in several places by displacedequipment and other flying debris. As a result, a substantialamount of water leaked through the roof openings into the topfloor, causing considerable damage to the interior. In addition,the aggregate surfacing blew off, damaging glazing on surroundingbuildings.4-12 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

Figure 4-7:Roof membrane startingto peel off at HancockMedical Center.Hancock Medical Center lost substantial portions of its metalroofing. Patients had to be relocated from the top floor to lowerfloors because of roof leakage (see Figure 4-8). West JeffersonMedical Center lost portions of roofing on the Psychiatry building,when the metal roof covering partially peeled off. The leadingedge began to peel back, but did not go any further than the edgeflashing, so a minimal amount of water penetrated through theroof. The psychiatry building was not occupied at the time becausethe hospital evacuated the building before the hurricane landfall.Figure 4-8:Roof damage on HancockMedical CenterOBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-13

The primary cause of window breakage was wind-borne debris.(see Figure 4-9). West Jefferson Medical Center had 76 windowsbroken, mainly by flying aggregate. Intensive care patients had tobe moved to the recovery room in the interior of the building andaway from windows. The Psychiatry building had rainwater penetrationthrough windows, even though they were not broken.Although many important hospital functions are located awayfrom the exterior windows, wind-blown rain can damage expensiveequipment even when it is located some distance fromthe broken window (see Figure 4-10). At West Jefferson MedicalCenter, the fitness center building sustained $250,000 worthof damage that resulted from water driven through the brokenwindows and from 30 days of high humidity, before the air-conditioningwas restored.Exterior doors were often pushed in by floodwaters and blownopen and damaged by wind pressure. Breakaway doors are particularlyvulnerable to opening in high-wind conditions, as windpressure can build up through the unsecured doors. Groundfloor entrance doors at Hancock Medical Center had to beblocked by sandbags and two-by-fours, both on the inside and theoutside, to stay closed (see Figure 4-11). The penthouse door atGarden Park Medical Center in Gulfport was blown off its hingesby strong winds.Figure 4-9:Broken windows at TouroInfirmary4-14 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

Figure 4-10:Broken windows at WestJefferson Medical CenterFigure 4-11:Blocked doors at HancockMedical CenterHancock Medical Center lost numerous fan cowlings and otherrooftop equipment, which left openings in the roof. Water penetratedthe building through these openings, reaching the firstfloor, and damaged boilers and other equipment. Vent openings inthe elevator penthouse in Touro Infirmary were blown off, allowingwater penetration. The water damaged the electrical and mechanicalequipment and controllers, shutting down the elevators.OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-15

West Jefferson Medical Center lost a number of cowlings andother covers causing water damage to equipment in the roomsbelow the roof. Some motors were sealed and continued to workduring the storm.All rooftop equipment should be safely secured to the curband stay in place during a high-wind event. Equipment thathas a high failure rate in high-wind events includes air-conditioningcondensers, HVAC units, exhaust fans and air intakeand exhausts.4.2.7 Utility Plumbing SystemsHospitals depend heavily on municipal services and other utilities.While it is possible to go into a minimal function mode and stillmaintain patient safety, certain utility systems must be operable.In many cases, Hurricane Katrina and the subsequent floodingpushed hospitals beyond the limits of even a minimal functionmode. Many had to be shut down, and the patients and staff hadto be evacuated. In addition to the loss of electrical power, themost common problem in maintaining the operations proved tobe the failure of water supply and sewer systems.Most hospitals lost water within a day or two following HurricaneKatrina’s landfall. Even when the water service was restored,it was suspected of contamination. Drinking water was in shortsupply in many hospitals. West Jefferson Medical Center receivedthree truck loads of bottled water from a local retailer in the aftermathof the storm, but other hospitals suffered from seriousshortages. A running water supply is critical for boilers to producesteam for sterilizing; for the chillers for the air-conditioningsystem; and for sanitary uses like toilets, washing dishes andlinens, bathing patients, etc. The most successful hospitals hadtheir own wells from which they pumped water using an emergencypower supply. The hospitals that stayed without water andan emergency power supply had to evacuate patients as quicklyas possible. As a consequence of this experience, West JeffersonMedical Center is planning to install two wells to provide bothsufficient capacity and redundancy. One well will service the centralplant boilers and chillers, and the other will be dedicated tohospital operations.4-16 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

Potable water service will likely be shut down during and immediatelyafter an event because of line breakages, lack of power to runpumping stations, or repair delays because of blocked roads andaccess routes. Hospitals, especially those in hurricane-prone regions,need a back-up water supply system in the form of:m Wells for exclusive hospital use should be supplied with theirown emergency generator to run the well pumps.m Water storage or water recycling systems on site should serve asa back-up to the central water supply.In many areas, the sewer system broke down shortly after thestorm arrived, either because of loss of power required to run municipalpumping stations, sewage back-up or shut down of sewagetreatment plants as a result of flooding, or because uprooted treesbroke the sewer lines. When the water and sanitary waste systemswere disabled, patients and staff were required to use hazardouswaste bags (red bags) taped to buckets or toilet bowls to managebodily waste. At West Jefferson Medical Center, used bags werestored in the hallways for several days and then buried on the hospitalsite for later disposal.Hospital design in hurricane-prone regions should also take intoconsideration the need to provide an onsite sewage-diversion andstorage system to prevent sewer backflows from disrupting hospitalsanitary system operations. Field observations indicate that in situationswhere the sanitary sewer system may be damaged, causing adisruption in service, functionality may be protected by:m Installation of an onsite septic tank as a sanitary back-upsystemm Installation of backflow devices in the sanitary lines to preventsewage from backing up into the hospitalm Designating, as part of the operations plan, a limited numberof sanitary systems to use in the hospital, so the onsite storagetank does not fill too quicklym Creating holding ponds for direct pumping of sewage, ifsufficient site area is availableOBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-17

4.2.8 Mechanical and ElectricalSystemsHurricane Katrina struck at a time when the temperatures duringthe daytime reached 95°F. Air-conditioning systems in hospitalswere generally not connected to the emergency power supply,nor was there any flexibility to switch emergency power from onesystem to another to provide some relief. The heat build-up was asignificant factor in creating difficult conditions for patients andstaff (see Figure 4-12).Lack of air-conditioning also allowed humidity to build up, whichcaused problems with switchgear, computers, and other electronicequipment. In many cases dehumidifying and coolingcould not resume for months after the event. The excessive humiditydamaged the electronic components of mechanicaland electrical equipment, such as fire alarm systems, elevatorswitchgear, or the telephone switchgear, as happened in TouroInfirmary. Mold growth in conditions of high temperatures andhumidity caused further damage. At West Jefferson MedicalCenter, rainwater and high humidity caused considerable damageto the fitness center, requiring all the electrical equipment tobe replaced. The ground floor at Hancock Medical Center wasflooded 3 feet deep; enough to cover all electrical outlets close tothe floor. The damage was irreparable.Figure 4-12:Toppled HVAC equipmentat Charity Hospital, NewOrleans4-18 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

Air-conditioning systems were also disrupted by a lack of waterneeded for water-cooled chillers, as happened in Garden ParkMedical Center in Gulfport when the municipal water servicewas shut down. Loss of air-conditioning resulted in interior condensation,and warm and humid air interfered with the normalfunctioning of electronic medical equipment.Measures to provide sufficient HVAC capacity for patient-occupiedand support areas and to protect the operation of the hospitalfrom humidity-related damages include the following:m Install emergency electrical generators with capacity to run theair conditioning system. This might also require water for thechillers if this is the method of delivering cold air.m Install sufficient controls in the hospital to be able to identifythe areas with mold and mildew problems, and have themcordoned off quickly.m Install HVAC duct cleanout locations, so that any mold ormildew that begins to grow in the ductwork can be easilycleaned out.m Create air-conditioning zones (where practical), so that crucialoperations can be cooled with a minimum amount of airconditioning.In a storm of Katrina’s magnitude, it is expected that power wouldbe lost almost immediately and for a considerable period of timethereafter. For example, Touro Infirmary lost power within minutesof being hit with wind gusts of about 60 mph. Since poweris so vital to maintaining functionality in critical facilities duringnormal periods, it is of paramount importance to provide anemergency power supply for all critical hospital functions.Most hospitals store up to 72 hours of emergency fuel on site.In the case of Hurricane Katrina, emergency generators neededto run continuously for 5 days or more. Many hospitals hadto obtain fuel for their generators from outside sources, usuallythe military. West Jefferson Medical Center got fuel from anearby Navy ship. Hancock Medical Center had one of their undergroundemergency generator fuel tanks flooded, with waterOBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-19

covering the fill cap and all vent openings. They could not usethis tank, fearing that contaminated fuel would damage thepower generators.The capability to switch power to different locations at differentpoints in time is one of the most important features ofemergency power supply systems. However, most of the wiringsystems in facilities affected by Hurricane Katrina were not setup with this capability. Emergency power in most cases was notavailable to run the air-conditioning systems. Redundancy in theemergency power systems that would have allowed maintenanceand repair without disruption was lacking in most cases.Portable generators, where they existed, were invaluable. Theycould be moved around as needed, but the problem of outsideventilation was difficult to overcome when the power wasrequired away from vent openings. Use of generators indoorsis extremely dangerous and should not be attempted in anycircumstances.More and more hospitals are dependent on computerized systemsfor patient medical records, transmission of X-ray film and otherimages, reporting laboratory results, patient physiological monitors,and a myriad of other uses. Once the power is lost, thesesystems are shut down unless they are on emergency power.Piped oxygen and nitrous oxide supplies are essential for manypatients. With electrical systems out, pumping of medical gaswas not possible. Most of the hospitals maintained tanks of oxygenthat could be brought to the bedside (Figure 4-13), butonce the emergency supplies of medical gas ran out, the patientsat serious risk had to be evacuated.The experience of hospitals during Katrina indicates that therequirements for emergency power should have high priority.Generators should be located above the base flood elevation, beprotected from flying debris, and have appropriate exhaust ventsystems installed. Fuel storage tanks should be located abovethe flood elevation, or adequately anchored to ensure that thetank will not float off its foundation under pressure from risingfloodwaters. Hospitals in hurricane-prone regions should storesufficient fuel to support running generators at full load for at4-20 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

least 96 hours (4 days). Emergency power distribution systemsshould be able to provide power to every system in the hospital,and have switching capabilities to shift loads to different parts ofthe hospital as needed.Figure 4-13:Oxygen supplies atHancock Medical Center4.2.10 Communications SystemsHospitals have a variety of communications systems in addition to theusual telephone and e-mail systems. Many of these are for emergencycommunications with ambulances and other emergency supportservices. These include satellite telephones, government line telephones,ham radios, internal radio systems, nurses’ call systems, andwireless systems of various sorts. Communications systems are criticalfor medical uses, but during a storm like Katrina, the ability to contactfamily members and friends to check on their status meant a lotto both the staff and the patients. The importance of being able to getnews from outside, to request restocking of supplies, and to arrangeevacuation of patients became obvious in the aftermath of Katrina.One consistent theme in damage reports was that satellite disheswere toppled, rendering satellite phones, one of the main sourcesof emergency communications, inoperable. Antennae used forOBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-21

emergency communications frequently broke, disconnecting thehospital systems from the outside world. Hancock Medical Centerlost not only the satellite dish, but also the dish for the educationsystem and its television antennae. West Jefferson Medical Centerlost only one antenna.External communication isn’t the only important link thatcan be broken during a hurricane. Internal communications(for example, from surgery to the nursing floor, or from thenursing floor to the supply storage areas) are critical to maintainfunctionality.At Hancock Medical Center, the only means for internal communicationswere 5-Watt Motorola radios. These continued to workwell, and were relied upon exclusively when the telephone switchgearflooded and broke down. West Jefferson Medical Center alsoused radio communication that continued to work throughout thestorm. Cellular phones also worked, until the transmission towerwas toppled. Hospitals that had ham radio operators bring theirequipment in, or had a ham radio set-up in the hospital, foundthis system very important and useful. Several hospitals plan tohave ham radios available for future emergencies.Charity Hospital and West Jefferson Medical Center lost their computersbecause the computer network power supplies were notwired into the emergency power supply grid. John Hancock MedicalCenter also lost its computers when the ground floor flooded(see Figure 4-14).Since many communication systems are dependent on externalnetworks that may be out of commission, roof antennae should bewell anchored, or mounted inside of penthouses. Satellite dish antennaemay have to be taken down prior to a hurricane and putback after the storm had passed. Finally, redundancy of systems isimportant, as proven during Katrina—one system may work whereothers do not.4-22 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

Figure 4-14:Damaged computernetwork equipment atHancock Medical Center4.2.11 Nonstructural and OtherSystemsNonstructural systems, among others, include interior non-loadbearingwalls, ceilings, and floors. In hospitals flooded with stormsurge, floors were destroyed and gypsum board walls were soaked.At Hancock Medical Center the water level reached 3 feet. Thehospital must replace all the flooring material, rewire the outlets,and replace the wall sheathing at a level about 2 feet above thehigh water mark (see Figure 4-15).In many hospitals humidity buildup damaged floor and ceilingtiles. Touro Infirmary had to replace 60,000 square feet of tileflooring and all of the ceiling tiles in the hospital because of humiditydamage. The loss of air-conditioning at West JeffersonMedical Center caused the buildup of humidity in the air, leadingto water condensation on terrazzo floors, making them veryslippery.Security was a major issue for most New Orleans hospitals. Membersof the community naturally sought the hospital for shelterwhen their homes were destroyed. When the water rose, peopletrapped in the city followed the water’s edge to the Touro Infir-OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-23

mary and West Jefferson Medical Center, where crowds of peoplecongregated on the front doorsteps. Attempted break-ins andlooting were reported, which prompted hospitals to barricadedoors, post armed guards at entrances, and “lock down” so thatno one could either enter or leave. At University Hospital, thedoors were removed and the entrances sealed up.Hospitals that allowed families to come in with the staff for theduration of the storm encountered numerous problems after afew days. Many of the family members became restless becausehospitals had no appropriate accommodations for them. This becamea security problem, as it was important to keep guests awayfrom the patients and their caregivers.Figure 4-15:Drying of flooded groundfloor at Hancock MedicalCenterFire safety should be a concern during a storm since the firerisks are usually greater than at other times. Although the firealarms are normally connected to emergency power, other typesof damage made them inoperable. At Touro Infirmary, thebuild-up of humidity knocked out the electronic components ofthe fire alarm system. After the storm, 470 points needed to berepaired before the system was fully operational again. At WestJefferson Medical Center, the fire alarm system was undamaged,4-24 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

ut the line to the fire station was cut. Heat-activated fire suppressionsystems continued to function where sufficient waterpressure was available, but dry standpipes might not have beensupplied with water in the event of a fire. Directional signs inmany hospitals were blown away. In the rush for care after thehospitals were accessible, it was necessary to put up temporarysignage to route the large volume of visitors and patients to theright destination.4.2.12 SummaryThe General Accounting Office (GAO) report to Congress on theevacuation of hospitals and nursing homes noted that administratorsshould “consider several issues when deciding to evacuateor to shelter in place, including the availability of adequate resourcesto shelter in place, the risks to patients in deciding whento evacuate, the availability of transportation to move patientsand of receiving facilities to accept patients, and the destructionof the facility’s or community’s infrastructure.” For new facilities,most of these issues can and should be addressed duringsite selection, risk assessment, and application of the appropriateplanning and design recommendations described in this manual.For existing facilities, careful evaluation and consideration of therecommendations provided in this manual should help ensuregreater resilience during flooding and high-wind hazard events.In this way, communities can continue to depend on these facilitiesboth for the care of existing patients and the care of peoplein disaster emergencies.OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-25

4.3 EDUCATIONAL FACILITIES4.3.1 BackgroundEducational facilities are considered critical facilities because,apart from their vital role in educating children, they arefrequently used during and after a storm as emergency shelters,or as staging centers by the National Guard, law enforcementpersonnel, or critical infrastructure repair crews for emergencyoperations. Educational facilities, in this case mostly K-12 schoolbuildings, are generally equipped with food preparation facilities,well distributed sanitary facilities, and ample space for personneland equipment.The primary function of a place of refuge shelter is the protectionof the occupants during a storm. This function is dependenton preservation of the structural integrity of the building andthe building envelope. The failure of a structural component ora breach in the building envelope can lead to casualties and canmake the buildings unusable as a recovery shelter after the storm.Educational facilities planned for use as place of refuge sheltersmust, above all, protect the lives and well-being of evacuees. To doso, they must be constructed to withstand storm surge or inlandflooding and wind impact. This means that they must be locatedin areas that minimize these storm effects. If they are located inthe areas subject to flooding and high-wind hazards, they need tobe constructed to preserve full functionality, with uninterruptedelectricity, communications, water, and sanitary service. This will4-26 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

also allow them to serve as recovery shelters. Educational facilitiesthat may not have served as shelters during the storm, becauseof their proximity to the coast or their susceptibility to inlandflooding, may be useful as recovery shelters provided they are ableto survive the hurricane intact.The primary function of a recovery shelter is to provide a locationfor resources and manpower after the storm has passed, to centralizethe command and distribution functions for recovery workin the community. Recovery shelters require that all building functionsand services remain usable in the aftermath of a storm. Theyare often used by the American Red Cross (ARC), National Guard,or other government agencies as a distribution point of first aid,food, water, and other supplies. They also serve as management orinformation dissemination hubs concerning recovery efforts.The following facilities were visited for the preparation of thismanual:m Charles P. Murphy Elementary School (Pearlington, Mississippi)m Pass Christian Middle School (Pass Christian, Mississippi)m St. Stanislaus High School (Bay St. Louis, Mississippi)m Northbay Elementary School (Bay St. Louis, Mississippi)m Hancock High School (Kiln, Mississippi)m Pineville Elementary School (Pass Christian, Mississippi)m D’Iberville High School (D’Iberville, Mississippi)m D’Iberville Middle School (D’Iberville, Mississippi)m Lyman Elementary School (Gulfport, Mississippi)m East Hancock Elementary School (Hancock County, Mississippi)m Saucier Elementary School (Saucier, Mississippi)m Port Sulpher School (Port Sulpher, Louisiana)OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-27

4.3.2 Effects of FloodingThe most devastating damage to educational facilities during HurricaneKatrina was caused by the storm surge. FEMA reporteda storm surge of 20 to 30 feet above normal tide levels. In someplaces the flooding extended up to 6 miles inland. The effect oncoastal communities was catastrophic, because most buildingswithin a quarter of a mile of the shore were virtually washed away,while most of the remaining buildings beyond this area were severelydamaged. Virtually all of the educational facilities in PassChristian, Mississippi, were heavily damaged as a result of theirproximity to the coastline.Inland flooding occurred in low-lying areas farther away from thecoastline. D’Iberville Middle School had approximately 8 feet ofwater, but was not used as a shelter because the school districtstaff was aware of the potential for flooding from past experience.The structural integrity of the school was not compromised by theflooding, but the water damage to the interior was substantial (seeFigure 4-16).Figure 4-16:D’Iberville Middle Schoolwas flooded to the depthof 8 feet4-28 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

The experience of Hurricane Katrina shows that the damagecaused by rising water generally renders shelters uninhabitableand useless, further aggravating the recovery process. In most casesthe mechanical and electrical systems were disabled as a result offlooding, which allowed the internal temperatures to reach intolerablelevels. Additionally, the flood-induced back-flow of plumbingsystems created unsafe sanitary conditions in most of the facilities.4.3.3 Effects of High WindsHurricane Katrina reached maximum gust wind speeds of 130mph at landfall, with hurricane force winds extending outward105 miles from the center of the storm (FEMA, 2006). Numeroustornadoes were also spawned by the hurricane, contributing tofurther damage as the storm moved northward. There were 11 tornadoesrecorded in Mississippi, with 17 more in Georgia, and 4in Alabama. Current model building codes in the areas affectedby Hurricane Katrina generally require buildings to be designedto meet 120 to 150 mph design wind speeds. Some buildings,however, were constructed prior to the implementation and enforcementof the current model codes.Wind damage was most evident on the building envelope, especiallyroofs, walls, doors, and windows, as well as other exteriorelements, such as walkway canopies and exposed mechanical andelectrical equipment. The extent of the damage was dependenton the force of the wind, the type of construction, and the configurationof the buildings. Once a building envelope was breached,the interior of the building sustained additional damage, both asa result of pressurization and rainwater penetration. The most severedamage in the interior was observed on the least durablefinishes, such as acoustical ceilings, wood doors and trim, andbuilding contents such as office equipment, furniture, and books.Most of the educational facilities used as place of refuge shelterssuffered wind damage to the roofs and windows. When a portionof the roof was lost or a window was broken, rainwater was ableto enter the building, causing damage to the interior. In some instances,the occupants were forced to relocate to other buildingsduring the storm, because of the danger of progressive buildingfailure (see Figure 4-17).OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-29

Figure 4-17:Broken windows atD’Iberville High School4.3.4 Site SelectionMost educational facilities that were destroyed or severely damagedby Katrina were located in the areas subject to storm surgeflooding. Ideally, educational facilities used as shelters shouldnot be located in floodplains, but since they must be located inproximity to the neighborhoods they serve, some are built onflood-prone sites. Even if buildings can be elevated to reduce thepotential for damage, the surrounding area remains susceptibleto flooding, which could prevent access and disrupt the deliveryof emergency aid. This also underscores the need to provide multipleroutes to and from a facility, in case of roadway blockagefollowing a storm.Pineville Elementary School near Pass Christian, Mississippi, wasused as a place of refuge during the storm, but when the waterrose to a depth of 2 feet, the people had to be moved by schoolbuses to another shelter (see Figure 4-18). The buses were drivenby school bus mechanics struggling to maintain control in risingwater and 80 mph winds.The schools in Pass Christian—mostly one-story buildings locatedin mapped flood hazard areas—sustained heavy damage from4-30 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

storm surge flooding. The massive storm surge devastated parts ofNorthbay Elementary School in Bay St. Louis, Mississippi, a singlestorybuilding located in a mapped flood zone. Exterior wallscollapsed, and most of the interior and contents were destroyed(see Figure 4-19).Figure 4-18:Pineville ElementarySchool shelter had tobe evacuated when thefloodwaters started to rise.Figure 4-19:Exterior walls at NorthbayElementary SchoolOBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-31

St. Stanislaus High School in Bay St. Louis, although located righton the coast, was on naturally higher ground, and only the firstfloors were affected by the storm surge. Within a few months afterthe storm, the second floors in some of the buildings had been repaired,including restored power, water, and sanitary service, andwere back in use (see Figure 4-20).Figure 4-20:Lower floors washed awayby the storm surge at St.Stanislaus campusConsiderable damage occurred in low-lying areas that wereflooded by storm surge ranging in depth from 2 to 8 feet. Suchwas the case at D’Iberville Middle School in D’Iberville, Mississippi,which sustained severe damage, including the destructionof many exterior walls, when water rose to nearly 8 feet above thefloor. Fortunately, it was not used as a shelter, unlike the nearbyD’Iberville High School, which is a designated shelter. The highschool is built on higher ground and was not affected by flooding.4.3.5 Architectural DesignGenerally, educational facilities have centrally located corridors(with classrooms or other spaces on both sides) that have ready accessto sanitary facilities, are at least 8 to 10 feet wide, and are freeof all obstructions. These features make them ideally suited for4-32 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

emergency shelter use. Although there are a few exterior openingsthat can be breached by a storm, the hallways are generallywell protected from outside elements. It should be pointed out,however, that in situations where the roof or the exterior walls fall,interior corridor walls may collapse as well. The corridors are usuallyunfurnished and readily available for a variety of functions.They served well as safe areas during the storm, with only a few notableexceptions. At the D’Iberville High School, the corridors hadunprotected windows at each end. These windows were brokenduring the storm and it was necessary to move people into anotherbuilding. Unfortunately, there were no enclosed walkways orinterior corridors connecting the buildings, and it was necessaryto go outside into the storm to reach the other building. Similarly,when the roof structure at Lyman Elementary School shelterstarted to fail, it became necessary to take the refugees outside beforethey could reach safety in another building (see Figure 4-21).For hurricane shelter safety, it would be beneficial to have all ofthe buildings connected with enclosed corridors, to allow safermovement between buildings during a storm. Other componentsof the building envelope would have to be sufficiently resistantto wind and wind-borne debris impact to protect the occupantsand the services they need. School corridors in particular shouldeither have impact-resistant (or protected) windows or none at all.All exterior doors should also be designed to meet hurricane windloads and wind-borne debris impact requirements, as described inSection 3.4.3.1).Figure 4-21:Collapsed portion of theLyman Elementary SchoolBuildingOBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-33

4.3.6 Structural SystemsMost of the educational facilities observed were one-story buildingswith concrete slab-on-grade foundations constructed usingconcrete masonry load-bearing walls and steel-framed roofs.The roof joists were supported either by masonry walls or steelbeams. Some facilities, like the East Hancock Elementary School,used pre-engineered systems consisting of rigid steel frames supportinga standing seam metal roof. Pass Christian Middle Schooland Saucier Elementary School used structural steel frameswith standing seam or built up roofs. St. Stanislaus High School,located on the coast, had a concrete structural frame where thefirst floor was heavily damaged by the storm surge, but the foundations,concrete structure, and the upper floors survived. This wasbecause the buildings on campus were located on higher groundthan the surrounding area.The storm surge exerted tremendous forces on the buildings in itspath, first as the water rose, and again when it receded. The forceswere strong enough to knock down exterior masonry walls, as happenedin the Northbay, Charles B. Murphy, Pass Christian, andPlaquemines Parish schools (see Figure 4-22). In most cases, themain structural components survived with little or no damage.Figure 4-22:Damaged exterior wallsat Charles B. MurphyElementary School4-34 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

Designing the connections between structural components accordingto loads is critical to maintaining the load path andthe structural integrity of school buildings in hurricane-proneregions.4.3.7 Building EnvelopeNewer educational facilities located some distance from the coastsustained mainly wind-induced damage to the building envelope,primarily to roof coverings and windows. Facilities located alongthe coastline were hit by the storm surge that destroyed most ofthe building envelope on the ground floor, including large sectionsof exterior walls. The walls collapsed under flood loads thatexceeded all expectations.At Charles P. Murphy Elementary School, many of the infill masonrywalls were displaced, and the concrete slabs on grade wereuplifted and severely cracked in several classrooms (see Figure4-23). A similar slab failure also occurred at D’Iberville MiddleSchool. The cause of this type of failure was an increase in upwardhydrostatic pressure below the slab, causing it to burst upward.Figure 4-23:Cracked concrete floorslab at Charles B. MurphyElementary SchoolOBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-35

The St. Stanislaus High School campus consists of several buildingsthat used different exterior wall systems, including masonryand precast concrete panels. The masonry walls on the first floorwere heavily damaged by the storm surge, but it appears thatthe precast concrete panels withstood the force of the hurricanemuch better (see Figure 4-24). Large sections of the exterior masonrywalls at St. Stanislaus, as well as in Northbay Elementary inBay St Louis and Port Sulphur schools in Plaquemines Parish, collapsedunder the pressure from storm surge (see Figure 4-25).Figure 4-24:Precast concrete panelingat St. Stanislaus HighSchoolFigure 4-25:Collapsed exteriormasonry wall at PortSulphur school campus4-36 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

The exterior brick veneer walls at the Pass Christian Middle Schooland at St. Stanislaus cracked and separated from the wall framingunder the impact of storm surge (see Figure 4-26). This kind ofdamage usually results from a failure of brick ties that did notmanage to hold the brick in place. In many cases these attachmentscan corrode and allow the brick veneer to move under lateral pressure.Such damage allows the penetration of water into the interior,where additional damage to building contents is inevitable.The wind-induced damage was limited primarily to the roof componentsat the edge, such as flashing and coping. More substantialdamage occurred on a building at St. Stanislaus campus and atHarrison 9th Grade gym, where large sections of metal roof coveringwere blown away (see Figure 4-27). The standing seam metalroof panels peeled back and away from the roof framing, exposingthe interior to rainwater and additional wind damage.Typically, glazed doors, windows, and roof coverings are thebuilding envelope components most susceptible to damage causedby wind-borne debris. Although glass or shutters designed to resistsuch wind-borne debris are available, none of the educationalfacilities had protection on the windows and doors. The corridorwindows at D’Iberville High School were broken during the storm,which prompted the complete evacuation of the building.Figure 4-26:Cracked brick veneer atSt. Stanislaus High SchoolOBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-37

Figure 4-27:Metal roof covering peeledaway at a St. Stanislauscampus buildingFor buildings located in flood hazard areas, especially areas notsubject to storm surge, elevation well above the predicted floodlevel is the most effective damage-reduction measure. Dry floodproofingmay be used to provide some degree of protection,although if floodwaters rise higher than the designed level ofprotection, the damage can be catastrophic. This technique, generallyfeasible for flood depths of only 2 or 3 feet, is expensiveand difficult to implement on existing buildings. Depending onthe expected depth of water, local soil properties, and the sizeand location of openings, the facilities can be designed to limitwater infiltration through the walls, openings, and conduits, andprevent envelope failure due to excessive hydrostatic pressure.Dry floodproofed buildings must have detailed emergency plans,with clear instructions for deployment of devices and other measures.Lack of periodic maintenance can render floodproofingmeasures ineffective.Another alternative for minimizing structural damage to existingbuildings is to provide wet floodproofing. This approach, which isnot allowed for new construction, allows water to flood the lowerfloors protected with water-resistant materials and finishes thatcan be easily cleaned and restored.4-38 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

4.3.8 Utility SystemsEducational facilities are typically not equipped with emergencyback-up systems, but are mostly dependent on municipal waterand sanitary systems. The breakdown of municipal water andsewer services, caused by power outages which shut down watertreatment plants and pumping stations, adversely affected most ofthe facilities. Although a few of the facilities affected by HurricaneKatrina were served by onsite wells and some had septic systems,lack of power prevented their full use. The sanitary sewer systembacked up under pressure from floodwaters and, together withthe loss of water service, created great difficulties inside facilitiesused as shelters.The sanitation problems, especially the unpleasant odors that permeatedthe facilities, combined with high humidity and heat,posed a serious health risk. At the D’Iberville High School, theloss of water prompted volunteers to haul buckets of water from anearby ditch to be used for flushing the toilets. After the storm hadpassed, portable toilets and showers were brought in by the ARC.4.3.9 Mechanical and ElectricalSystemsMost mechanical systems depend on the exterior equipmentmounted on the roof or attached to the exterior walls. The exposedequipment is the most vulnerable element in the system,because it is commonly damaged by floodwaters, strong wind,and wind-borne debris. Rooftop equipment, such as air-handlingunits and exhaust fans, typically were not adequately anchoredto meet the hurricane-force winds and were frequently damagedor toppled. Through-wall fan coil units installed below classroomwindows at the Charles P. Murphy Elementary School in Pearlingtonwere ruined by rising floodwaters (see Figure 4-28).As a result of HVAC failures, conditions in shelters became veryunpleasant because of the heat build-up and the lack of ventilation.The interior temperatures and humidity rose to unbearablelevels because of the hot weather that followed Hurricane Katrina.Without the advantage of sufficient natural ventilation, theatmosphere quickly became stuffy. Undamaged mechanical equip-OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-39

ment, especially HVAC systems, was not operational because ofthe power outage and the lack of emergency power supply. AtD’Iberville High School, the principal reported using a generatorto run a large portable box fan in the corridors to provide somerelief. The same generator also provided power for night-timelighting in the corridors.The Harrison County School District office was one of the fewbuildings equipped with a generator, and for that reason it wasused as an EOC. It served as a command center and providedsleeping and dining facilities for emergency crews. The success ofthis experience reinforces the importance of having emergencypower generator systems and a sufficient fuel supply. Emergencygenerators should be in a protected enclosure and at an elevationhigh enough to prevent flooding.Figure 4-28:Damaged HVAC unitat Charles B. MurphyElementary School4.3.10 Nonstructural and OtherSystemsIt is essential to the operation of educational facilities used asplace of refuge and recovery shelters that communications systemsremain operational. The place of refuge shelters had a4-40 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

variety of communications systems at their disposal at the beginningof the storm. This included the phone system, cellulartelephones, school system radios, and police and fire radios.These systems proved to be unreliable during the storm whenantennae and utility lines were damaged. Immediately after thestorm, all communications had to be handled through messengers,until portable antennae were brought to restore both cellphone and radio service. The Harrison County school boardis now considering the purchase of satellite phones to be usedduring emergencies.Nonstructural components and contents of educational facilitiessustained the greatest damage from flooding. At D’IbervilleMiddle School, all interior wood doors, frames, trims, casework,fan coil units, and furniture typically suffered severe damagefrom water exposure.The majority of interior walls were constructed of un-reinforcedconcrete masonry. Portions of these walls and some exterior nonload-bearingwalls at Charles P. Murphy Elementary School wereknocked down by the storm surge (see Figures 4-29 and 4-30). Ifthe buildings had been occupied during the storm, people couldhave easily been injured by falling debris. Although many of thesewalls are used as partitions and are consequently not load-bearing,their mass poses a threat to life and property should they collapse.Figure 4-29:Damaged non-loadbearingwalls at CharlesB. Murphy ElementarySchoolOBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-41

Figure 4-30:Interior damage at CharlesB. Murphy ElementarySchool4.3.11 Equipment and AuxiliaryInstallationsSchool equipment is not necessarily important for the operationof emergency shelters, except for kitchen and dining facilities.Schools that sustained flooding damage usually had all their foodpreparation and refrigeration equipment ruined. The equipmentstored outside consists mainly of buses and other vehicles.In Pass Christian, many of the school buses stationed in the townwere destroyed by the storm surge (see Figure 4-31), although someof them were used during the storm to move people from PinevilleElementary School to another shelter because of rising water.The Harrison County School District moved all of its buses fartherinland before the storm, which ultimately proved prudent and allowedthe buses to remain available for use after Katrina. In theaftermath, Harrison County School District had no fuel supply tooperate the buses or other vehicles. Several years ago, the schooldistrict opted to issue gasoline cards to the bus drivers to fill up atvarious gas stations rather than at a central depot. After the stormthere were few gas stations operating, and it became a time-consumingprocess to get fuel for any vehicle. In the future, HarrisonCounty School District intends to have its own gasoline supplyavailable on generator power to ensure that school vehicles arekept operational.4-42 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

Figure 4-31:School bus washed awayby the storm surge4.3.12 SummaryEducational facilities intended to serve as emergency shelters,together with accompanying parking lots and access roads servingthese shelters, should be located inland, away from the coast, andon high enough ground to avoid flooding. Educational facilitiesthat are built closer to the shore because of the school districtboundaries should be constructed with the first floor above thehighest expected storm surge level. These educational facilitiesshould not be used as shelters during a hurricane, but couldserve as relief centers after the storm, as long as they do notsustain significant damage. No educational facilities should beconstructed within the immediate area along the shore, wherewaves are the strongest.Based on observations, the most resilient school buildings arebuilt using reinforced concrete structural systems, or reinforcedmasonry construction. The best performing roof decks werecast-in-place concrete, precast concrete, or concrete toppingover metal deck. Reinforced concrete or reinforced concretemasonry exterior and interior walls, including precast concretepanels and tilt-up concrete wall panels, seem to have sustainedthe least flood damage. Other observations indicate that thefollowing measures may help reduce the damage in hurricaneproneregions:OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-43

m Doors should be designed to meet the positive and negativedesign wind pressure and impact resistance, as recommendedin Section 3.4.3.1. Windows should use impact-resistant glazingor shutters.m Educational facilities that will be occupied during a hurricaneor needed within a few weeks afterwards should be equippedwith an emergency generator.m All shelters should have protected communications systemslinked to the EOC.m Exterior corridors should be enclosed to allow full accessbetween buildings, so that no one is forced to go outsideduring a storm to get to another area of a building.m All educational facilities intended for use as evacuation sheltersshould be designed according to FEMA 361 guidelines.4-44 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

4.4 EMERGENCY RESPONSE FACILITIES4.4.1 BackgroundEmergency response facilities include EOCs, police stations,and fire rescue stations. All of these facilities areconsidered critical because they must remain functionalto manage response and recovery operations during and aftera hazard event. EOCs function as incident command centersfor coordination and support of all emergency activities. Thecommand and response personnel must remain on duty, in fullreadiness for action both during and in the aftermath of a disaster.In addition to personnel and resources, EOCs house theinformation and communications systems that provide feedbackto the emergency managers to help them make decisions aboutefficient and effective deployment of resources. They also relayinformation to local residents, shelters, media, and other firstresponders, while providing Continuity of Government (COG)and Continuity of Operations (COOP).Police and fire rescue facilities are critical to disaster response,because an interruption in their operation as a resultof building or equipment failure may prevent rescue operations,evacuation, assistance delivery, or general maintenanceof law and order, which can have serious consequences for thecommunity.While each of the three types of emergency response facilitiesis used for different operational purposes and their needs areOBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-45

different, most of them require and depend on the followingfacilities:Back-Up Communications Equipment: Conventional communicationsthat rely on radio towers with repeater systems cannot be reliedupon during high-wind events, because of the high probabilitythat the towers will lose power, as occurred in many jurisdictionsin Mississippi and Louisiana. All facilities need back-up communicationssystems such as very high-frequency (VHF) and hamradios, and adequate back-up communications equipment.Accommodation Space: Adequate space for all the essential personnelto work, with provisions made for continuous operations,such as sleep areas, kitchens (with supplies for all duty personnel),laundry facilities, and shower facilities for all such personnel. Itshould also be noted that many residents view the local fire stationas a point of shelter, and will seek it as a refuge when winds andconditions become dangerous in their own homes.Situation Rooms: “Meeting rooms” in which to conduct local governmentbusiness as well as confer with community members,media, and government officials, and for press conferences anddissemination of information.Safe Equipment Storage: Patrol and rescue vehicles and other equipmentmust be adequately protected from flood waters, wind-bornedebris, and driving rain, and be accessible and readily available foremergency use.The observations included in this section are based on the examinationof the following facilities:m Harrison County EOC (Gulfport, Mississippi)m Jackson County EOC (Pascagoula, Mississippi)m New Orleans EOC (New Orleans, Louisiana)m Hancock County EOC (Bay Saint Louis, Mississippi)m Orleans District Levee Board Police Department (NewOrleans, Louisiana)4-46 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

m New Orleans Police Department (New Orleans, Louisiana)m Gulfport Police Department (Gulfport, Mississippi)m Pass Christian Police Department (Pass Christian, Mississippi)m New Orleans Fire Department (New Orleans, Louisiana)m Gulfport Fire Department (Gulfport, Mississippi)m Pass Christian Fire Department (Pass Christian, Mississippi)m Cuevas Volunteer Fire Department (Pass Christian,Mississippi)m Back Bay Fire Company #3 (Biloxi, Mississippi)4.4.2 Effects of FloodingFlooding during Hurricane Katrina, especially the impact of thestorm surge and levee failures, caused heavy damage that disruptedthe long-term functional capabilities of the emergencyresponse system.The facilities damaged by rising water were generally rendereduninhabitable after the water receded. As a result, theemergency response teams were forced to relocate the operationselsewhere. Evacuation and relocation was common amongdamaged fire rescue and police facilities and affected their operationson many levels. Firstly, relocating farther away from theirservice areas meant that the response time to emergency calls increasedsubstantially. Secondly, the response teams were forcedto operate from temporary accommodations with inadequate facilitiesthat were frequently overcrowded. Thirdly, new facilitieslacked adequate supplies and services for the extra personnel,which required numerous improvisations, further hampering theoperations.OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-47

4.4.3 Effects of High WindsThe highest gust wind speeds during Hurricane Katrina were typicallybelow the design wind speeds for this area, which rangefrom 120 to 150 mph. Despite this, many emergency response facilitiessustained damage that disrupted their operations, and in afew cases shut down the facility. Most of the damage was confinedto the building envelope. Portions of metal roofing were liftedand peeled off; aggregate roof surfacing was blown off, becomingwind-borne debris; and roof-mounted equipment, including communicationtowers and antennae, were toppled or broken. Metalwall-cladding panels detached or peeled off on a number of facilities,exposing the interior to pressurization and rainwaterpenetration. Doors and windows were damaged by wind-borne debris,allowing the penetration of wind-driven rain.4.4.4 Site SelectionIdeally, the emergency response facilities should not be located ina floodplain or a site exposed to other types of hazards. However,emergency response facilities, especially fire rescue and police stations,must contend with geographic limitations pertaining to sizeand adequate coverage of their service areas that frequently placethem in hazardous locations. Many of the facilities flooded duringKatrina were located in designated floodplains. However, thisfact alone does not explain the catastrophic damage sustained byfacilities such as the police and fire stations in Pass Christian, Mississippi(see Figure 4-32), because most of the facilities damagedby flooding were built above the minimum required elevations.The primary reason for the widespread damage is the catastrophicnature of the flooding, caused by extremely high storm surge andthe failure of levees in New Orleans.In locations where the emergency response facilities were built toa higher standard than required by local regulations, the adverseeffects of Katrina were substantially reduced. The Jackson CountyEOC occupies the second floor of a municipal building locatedin Pascagoula, Mississippi. An examination of the storm surgeflooding associated with different hurricane scenarios indicatedthat the site would be inundated during a Category 3 hurricane.Consequently, the county decided to design the building to be4-48 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

approximately 4.5 feet above BFE (see Figure 4-33). During HurricaneKatrina, floodwaters rose to about an inch below the levelof the lowest floor. The building was not evacuated prior to thestorm, because it was believed that flooding would not exceed themaximum levels recorded during Hurricane Camille. As floodwatersstarted to rise, the decision was made to evacuate most of theoccupants to another building across the street. Despite this action,the EOC operations were not hampered significantly.The Pass Christian police and west side fire station were less fortunate,as the storm surge flooding at these sites far exceeded thebase flood elevation. It was estimated that the storm surge wavethat hit the police building was at least 15 to 20 feet high, whichrendered the building and the equipment stored inside totally unusable.The facility is currently looking at an alternative site onhigher ground as a possible site for relocation and construction ofa new station.The headquarters of the New Orleans Police Department hadapproximately 2- to 3-foot deep water on the first floor, and a completelyflooded basement (see Figure 4-34). The surroundingareas were also under water, isolating the facility and preventingits normal operation. All operations had to be transferred to otherpolice facilities in the city.Figure 4-32:Police station in PassChristianOBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-49

Figure 4-33:Jackson County EOCFigure 4-34:New Orleans PoliceDepartment HeadquartersThe Hancock County EOC in Bay St. Louis, Mississippi, is locatedon naturally high ground outside mapped flood hazard areas.Nevertheless, the floodwaters inundated the ground level, damagingthe interior finishes and practically destroying all equipmentand contents (see Figure 4-35). Most of the EOC’s operations weretransferred to an alternate location prior to Katrina’s landfall,most likely because the facility is mapped as part of an evacuationzone in case of a hurricane.4-50 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

Figure 4-35:Hancock County EOCSite characteristics and landscaping contributed significantly to theextent and type of damage sustained by these facilities. The GulfportFire Station #5 in Gulfport, Mississippi, experienced significant disruptionbecause of downed trees. One tree fell on the roof, causingminor damage, while two vehicles parked outside were severely damagedby the fallen trees. Furthermore, it took approximately 12hours of cutting the trees before firefighters were able to openthe access road and start responding to emergency calls. This experiencealso underscores the need to provide multiple routes intoand away from a site, in order to have redundancy and minimize thepossibility of isolation as a result of roadway blockage.The experience during Hurricane Katrina proved the efficacy ofpreventive evacuation of equipment and personnel to a safe andsecure location. It also proved wise to organize back-up facilities inother locations or in adjacent jurisdictions to serve as alternativecommand and operation centers. Emergency response facilitiesthat did so were better equipped to respond to citizens’ needs immediatelyafter the storm.4.4.5 Architectural DesignMany buildings used as emergency response facilities were notinitially designed for that purpose, or for operations under emergencyconditions. During and after Hurricane Katrina, most ofOBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-51

them experienced significant problems, irrespective of the levelof damage. Some of these facilities are located in existing buildingsdesigned as regular office space. These facilities performedpoorly, and although they were able to adapt to the circumstances,they did not operate as efficiently as those designed for their particularfunctions.For example, EOC facilities in New Orleans were placed into civiccenter offices, which were not equipped with kitchens, showers,and other facilities essential for the smooth and continuous operationof an EOC (see Figure 4-36). As a consequence, the facilityhad to be relocated immediately after Katrina because the availableaccommodations were insufficient and poorly equipped.Some of the buildings occupied by first responders were originallydesigned for a different purpose and subsequently converted totheir current use.Figure 4-36:New Orleans EOC in theCity Hall buildingGenerally, any building, whether new or old, that is used as anemergency response facility should be carefully reviewed for compliancewith the requirements for uninterrupted operation ofthe facility. Particular attention should be paid to issues that have4-52 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

historically caused problems in building or operational performance,such as:m Roof systems not designed for high winds and debris impactm Rooftop equipmentm Unprotected exterior glazingm Large, sectional and rolling doors not designed for high windsm Communications towersm Large roof overhangsm Lack of facilities for an extended length of stay, especiallyemergency sanitary facilities and power supplyBasements are another design feature with a high damage potential,especially when important services and facility functions arelocated there. The basement at the New Orleans Police Departmentcompletely flooded, and all the essential equipment located therewas severely damaged, crippling the facility for a long time. Observationsindicate that essential functions and service equipment shouldbe transferred from flood-prone basements to safer locations.The relatively new Back Bay Fire Company #3 station in Biloxi,Mississippi, was built in 1996, and yet its design does not reflectthe current needs of its occupants. The spaces are too small to accommodatethe duty shifts. The kitchen is inadequate for longerstays, while the sleeping area has unprotected, large, storefronttypewindows that represent a serious hazard in high-windsituations (see Figure 4-37). These minor architectural deficienciesmay be amplified during the times of crisis and adverselyaffect the operation of the facility, especially if combined withother building component failures.OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-53

Figure 4-37:Back Bay Fire Company#34.4.6 Structural SystemsConcrete and reinforced masonry have traditionally been the mostrobust structural systems for hurricane-prone areas, since theyhave a much higher reserve structural strength than other systems.During high-wind conditions, the added weight of the concretehelps counteract the uplift forces, while the mass and depth of concreteand masonry walls provides reserve structural strength thatprevents the walls from being breached during high winds andflood conditions. However, with precast concrete elements, attentionto design and construction of connections is important. Thiswas generally confirmed during Hurricane Katrina.The Jackson County EOC, located in Pascagoula, Mississippi, wasbuilt in 1977 and is an example of a structurally well-designed facility.The structure is composed of cast-in-place concrete, andperformed remarkably well (see Figure 4-38). Although the EOCis located on the second floor of the building, water only camewithin 1 inch of the ground floor, which is approximately 4 to 5feet above the surrounding grade. Other structural systems provento be resistant to flood and wind loads are steel or concrete framesthat are covered with precast concrete panels. These systems havevery high reserve capacities that perform extremely well duringhigh winds and storm surges.4-54 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

Figure 4-38:Reinforced concrete buildingfor Jackson County EOCIn contrast, pre-engineered metal buildings performed less well.Although the main structural components of most of these buildingsremained standing, suffering only light damage, the restof the building components were not able to resist the forces ofstorm surge. Two prime examples of these buildings are the PassChristian Police Department Headquarters and the Gulfport FireDepartment Station #7 (see Figures 4-32 and 4-39). Both of thesebuildings were severely damaged and all equipment stored insidewas destroyed.Based on the observations, many existing structures can be retrofittedto perform better during high winds. Although suchretrofits may be expensive and generally have limited capacity tostrengthen the structure, they definitely increase the overall structuralresistance. For example, roof decking can be retrofitted withadditional connections to provide increased uplift resistance. Furthermore,roof decks should be attached securely to make thebuilding diaphragm work as a unit and transfer loads adequatelyto the walls, while simultaneously preventing the deck from beingpulled from the structure during high winds.OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-55

Figure 4-39:Gulfport Fire Station #74.4.7 Building EnvelopeWhen the building envelope is breached, the interior is no longerprotected from the outdoor environment and the whole buildingis exposed to additional forces that may cause its progressivecollapse.The Gulfport Police Department Headquarters and the PassChristian Police Station are the prime examples of building envelopefailure. Both buildings, located near the coast, were exposedto the storm surge that crushed the lightly built exterior walls anddestroyed everything in the interior. Fire Station #7 was breachedby the storm surge, and practically the entire building envelopewas washed away, except for the roof deck. What remained of thebuilding was just a shell (see Figure 4-40). The duty personnel andmost of the vehicles were relocated to other facilities until a trailerwas provided as a temporary place of operations.On the other hand, the Gulfport Police Department Headquartersbuilding, constructed with heavy concrete masonrywalls, sustained no significant damage to the building envelope.The building only required restoration of flooded buildingcomponents.4-56 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

Figure 4-40:Exterior walls on theGulfport Fire Station #7washed away by thestorm surgeLongbeach Police Station sustained heavy damage to its rooftrusses, metal roof, and siding that allowed wind and rainwaterto saturate the interior of the building. The police officers hadto scramble to evacuate the prisoners and valuable records beforethey abandoned the building in the middle of the storm (seeFigure 4-41).Figure 4-41:Longbeach Police StationOBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-57

Third District Fire Station in New Orleans is a newer one-story,structural steel-framed building with brick veneer walls, metalfascia panels, steel roof deck, rigid plastic foam roof insulation,and metal roof panels. The estimated maximum wind speed atthis location during Hurricane Katrina was significantly lowerthan the design wind speed. Nevertheless, a large portion of themetal roof covering was blown off the apparatus bay (see Figure4-42). In some areas, the architectural metal wall panels withstanding seams covered by snap-on battens were still in place,but the batten covers had broken away. In other areas, the battencovers were still attached, but they had lifted—it appeared that fatiguecracks occurred along the standing seams (see Figure 4-43).Battens like these are frequently susceptible to blow-off, which allowswater infiltration and may lead to panel blow-off. Both thebattens and separated panels may become dangerous wind-bornedebris. This station was occupied at the time of the storm, butbecause of the extensive damage to the interior, apparatus baydoors, and the equipment, it could not be used and was consequentlyevacuated.Figure 4-42:Metal roof and wallpanels peeled off the ThirdDistrict Fire Station in NewOrleans4-58 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

Figure 4-43:Lifted batten covers onThird District Fire Stationmetal roofAlthough the estimated wind speed in Bay St. Louis was slightlylower than the design wind speed, the wind blew off most of theroof membrane from the Hancock County EOC, located in thecity (see Figure 4-44). The damage was initiated with the separationof metal edge flashing that had an uncleated vertical face. Inaddition to roof damage, the hardware on the exterior door failedand the door blew inward. As a result of rainwater penetration andflooding, most of the interior was ruined. Although most of thefacility operations were moved before hurricane landfall, the remainingbuilding occupants had to be evacuated during the event.Jackson County EOC in Pascagoula experienced similar damageto its roofing when the metal edge flashing peeled off and liftedportions of the roof membrane. However, the roof damage didnot cause water damage, because the cast-in-place reinforced concreteroof deck was capable of resisting rainwater penetration.The building’s reinforced concrete walls and roof deck resistedthe wind loads very well. The walls and roof deck were also extremelyresistant to wind-borne debris, as was the exterior glazingretrofitted with shutters that protected the openings.The edge flashing on low-slope roofs that usually initiatesthe peeling of roof membranes can be easily retrofitted withadditional screws, to prevent it from uplifting and causing a progressivefailure of the roofing system.OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-59

Figure 4-44:Roof damage at HancockCounty EOCFire stations are especially susceptible to breaches of the buildingenvelope, because of their large sectional and rolling doors thatare usually not strong enough to resist wind forces, and even lessso the hydrodynamic forces of storm surge. The apparatus baydoors failed in many fire stations affected by flooding. (see Figures4-39 and 4-45).Water and wind from the storm were able to penetrate the buildingswhen the doors were breached, causing subsequent damageto other systems and equipment. Large doors should be designedto withstand wind pressures and windborne debris impact as recommendedin Section 3.4.3.1.All doors and windows can also be replaced with modern, impact-resistantsystems that would reduce the chances of buildingpressurization and rainwater infiltration, which resulted in heavylosses to equipment and contents during Katrina. Rooftop unitsthat were blown off and damaged the building envelope by puncturingthe roof covering should be securely anchored to preventsuch damage in the future.4-60 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

Figure 4-45:Damaged apparatus baydoors at Port SulphurVolunteer Fire Department.4.4.8 Utility Plumbing SystemsFailures of public utility systems during Katrina were very common.Many first responder facilities were forced to improvise short-termsolutions until public utilities were restored. The Gulfport Fire DepartmentHeadquarters was able to back-feed water into its lines byisolating the building’s water supply lines from the public municipalsupply system. They then fed water directly into the building’swater lines in order to have water to shower and wash during thetwo weeks that they were without water in the facility. This capabilityshould be considered for all emergency response facilities, asit minimizes disruption of basic sanitary functions.In many facilities, flooding caused sewage to backflow into buildings,causing sanitary crises that directly affected their operations.Valuable time was spent cleaning up the facilities instead ofhelping others. To prevent this from occurring in future events theinstallation of backflow inhibitors (check valves) is recommended.The Pass Christian Fire Department managed the loss of sanitarysystems with plastic bags and buckets, while the staff at the GulfportPolice Department was able to acquire and use portable toiletsand bottled water until public utility systems were restored. TheJackson County, Mississippi, EOC is equipped with a pressurizedOBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-61

underground tank for toilets and washing, which supported the occupantsduring the 3 to 4 weeks that the facility was without water.The Cuevas Volunteer Fire Department in Pass Christian, Mississippi,was equipped with an underground septic tank, a drainfield, and a well, and did not experience significant disruptions inits plumbing and fresh water systems. These independent septicand fresh water systems do not rely on public municipal systems,and are preferred where possible as they virtually eliminate thechances of disruption during widespread outages.4.4.9 Mechanical and ElectricalSystemsHurricane Katrina also affected facilities by damaging or destroyingmechanical systems. Hurricane season occurs in thewarmest months of the year, and many of these facilities were notdesigned to allow natural ventilation. For example, the New OrleansPolice Department Headquarters Building is a multi-storybuilding where the main circuitry for the HVAC system, which waslocated in the basement, was severely damaged by the flood. Sincethe building was designed as a closed structure, natural ventilationwas a problem (see Figure 4-46). All the equipment located in thebasement needed to be completely rebuilt or replaced before thebuilding could be occupied again. In the interim, the entire departmentwas forced to relocate its operations to other facilities inthe city, placing a strain on facilities not intended to house additionalpersonnel and take on additional responsibilities.The inability to air-condition buildings because of damagedmechanical and electrical systems allowed internal temperaturesand humidity to reach intolerable levels, and in many buildingsmold began to form.Loss of electrical power during and after Hurricane Katrina affectedall other essential facility systems. Examples of this wereevident at all of the sites visited. Utility, mechanical, and communicationssystems became partially or completely unusable, eitherbecause emergency power was not available, or it had to be rationedas a result of overload or breakdown of generators.4-62 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

Figure 4-46:Fixed windows on NewOrleans Police DepartmentHeadquartersCuevas Volunteer Fire Department, located inland at Pass Christian,Mississippi, was without municipal power for approximately2 to 3 days, but, since its generator functioned properly, their operationswere only slightly affected by the storm. In contrast, theindoor generator and electrical panel at the Back Bay Fire Company#3 in Biloxi, Mississippi, became submerged in the flood,even though the generator was mounted several feet above thefinished floor. The water flooded the building, putting all the mechanicaland electrical equipment, including the generator, outof commission. As the water continued to rise, the firefighters andthe local residents that sought refuge in the station had to climbto the top of fire engines until the floodwaters receded.The New Orleans District 3 Fire Department Headquarters lostpower as a result of flooding. The generator was located outsideat grade level, and was ruined when approximately 2 feet of waterflooded the area (see Figure 4-47). The firefighters were forced torelocate to the nearby West Bank facility for 4 months, until powerwas restored at the headquarters building.Facilities that escaped deep flooding were typically operationalimmediately upon restoration of power. The Gulfport Fire DepartmentStation #1 had water barely enter the station, and was ableto get by on their generator for 3 days until municipal power wasrestored. Although their radios worked intermittently, they wereable to perform their search and rescue duties and use their newlyacquired chainsaws to help clear the roads of debris.OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-63

Figure 4-47:Generator mounted atgrade level damaged byfloodingThe need to provide a back-up generator at a safe and elevated locationis confirmed by the experiences during Hurricane Katrina.Many facilities were without power because of the low elevationand subsequent flooding of their generators. Jackson County EOChad its emergency power station elevated and protected in a separateenclosure, which allowed the facility to operate withoutinterruption (see Figure 4-48).Figure 4-48:Jackson County EOC’selevated generatorenclosure4-64 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

4.4.10 Communications SystemsIt is essential for the operation of emergency response facilitiesto keep their communications systems intact. Loss of communicationcapability prevents their primary function of responding tocommunity needs and adversely affects their ability to coordinatetheir actions. If the communications system malfunctions or becomesunavailable, the coordination between command centerswill be hindered, affecting management of the response and recoveryoperations during and after an event. Many jurisdictionsin New Orleans and along the Gulf Coast were cut off from eachother and could not communicate, even with their own departments.For example, one police officer from the Orleans DistrictLevee Board Police Department was in the heart of New Orleanswhen the city was flooded, and had no way of communicating withthe senior officials in his department. He worked for days with theofficers of the New Orleans Police Department (NOPD) assistingthe remaining residents in the city. For a period of days, he andhis partners from NOPD were operating without communicationscapabilities of any sort until the military arrived and issued themnew radios. It took approximately 2 to 3 weeks for communicationsto be re-established in a manner that resembled normalcy.The command and communications center for the police and firerescue departments in Pass Christian, Mississippi, was located inthe police department building, and was crippled as a result of thedestruction of their headquarters (see Figure 4-49). The landlinecommunications at the Jackson County, Mississippi, EOC continuedto function for a day or two, and other communicationssystems only experienced minor problems. The building was usedduring and after the storm.Hurricane Katrina experience indicates that alternative forms ofcommunication need to be available during and in the aftermathof a storm. High-frequency and ham radios that do not rely on repeatersystems should be in place, along with detailed instructionsand plans for their use in emergencies. Emergency power supplyfor communications systems must be available at all times. Thisrelatively low-cost solution would reduce the loss of communicationsduring and after future events.OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-65

Figure 4-49:Broken communicationsmasts at Pass ChristianPolice Station4.4.11 Equipment and AuxiliaryInstallationsSpecialized equipment such as vehicles, rescue equipment, andfire pumps were the most common types of equipment lost duringHurricane Katrina. Damage to vehicles and other equipment seriouslyaffected the operations, and frequently prevented speedyrescue and response efforts.In many cases throughout Mississippi and Louisiana, the vehicleswere stored immediately outside on facility parking lots while mostof the specialized equipment was stored inside in apparatus bays.In other cases, as in Pass Christian, Mississippi, the police departmentstationed its vehicles in a remote location that was thoughtto be safe, but the entire area flooded and all vehicles were rendereduseless. In Pass Christian the fire department, locatedapproximately a quarter of a mile from the coastline, had fourfirefighting trucks and two rescue trucks ruined during the storm,hampering firefighters’ efforts in responding to emergencies thatrequired the use of their equipment. Gulfport Police Departmentand the New Orleans District Levee Board Police Department deployedtheir vehicles all over the area to ensure that the vehicleswould be available on short notice after the storm.4-66 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

For the 2006 hurricane season, Pass Christian emergency responseplans include the evacuation of all vehicles to a staging site awayfrom the coastline, and away from trees and other objects that maybecome wind-borne debris. This geographic distancing of vehiclesfrom the coastline (and the area affected most by the storm andits surge) will protect key equipment and reduce the impact of afuture storm by allowing the first responders to be mobile shortlyafter the event. It should be noted, however, that many jurisdictionsin low-lying areas do not have safe staging sites at higherelevations or away from the coastline.Based on conversations with many emergency response crews thatwere affected by Katrina, the protection of their equipment andvehicles was a main consideration prior to the storm. Many jurisdictionsthroughout Mississippi and Louisiana decided to spreadtheir vehicles out to many locations thought to be safe, in order tobe certain that at least some of them would remain operational.This practice proved prudent and enhanced their abilities to respondin the immediate aftermath of the disaster. The vehiclesshould be sheltered in an area that is safe from flooding hazardand easily accessible after the event.4.4.12 SummaryEmergency response services are at the backbone of a community’sability to protect and save the lives and property of its citizensin any crisis. The provision of these services depends on the uninterruptedoperation of emergency response facilities duringand after a hazard event. This means not only that the buildingsthat house the crews and equipment must survive the onslaughtof flooding and high winds with minimal damage, but that all theequipment and systems necessary for emergency operations mustremain fully functional.Hurricane Katrina showed that emergency response facilitieshave a better chance of protecting their operations if they occupysolidly constructed buildings with sufficient reserve structuralcapacity that cannot be easily overwhelmed by a storm of this magnitude.It also showed that facilities with functional generatorswere better equipped to respond after the storm than those thatwere left completely without power. Since the facilities cannot op-OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES4-67

erate without adequate emergency power supply, all electricalsystems should be connected to power back-ups, and emergencygenerators should be elevated and protected against floodwatersand wind-borne debris.Mechanical systems need to be located in a sheltered area, wherethey will not be damaged by wind and flooding. Plumbing systemsshould be equipped with backflow inhibitors to prevent sewagefrom entering the structure during a flood. Provisions should alsobe made to allow the isolation of the building’s water supply, sothat it is possible to feed water directly into the building’s waterlines until municipal water supplies are restored.Finally, the lines of communication between community commandcenters and individual facilities must remain functional atall times. The basic communications systems need to be protectedagainst the effects of flooding and high-winds as much as possible,but as this storm showed, system redundancy is still the bestpolicy. In the event of damage, the facilities should have alternativemeans of communication that do not depend on local systemsand networks that could be damaged in the storm.4-68 OBSERVATIONS ON THE PERFORMANCE OF CRITICAL FACILITIES

AcronymsAAASHTOABFEADAARCASCEASTMASCE/SEIBFEBIABURC&CCMUDFEEIFSEOCEPDMFEMAFIRMAmerican Association of State Highway and Transportation OfficialsAdvisory Base Flood ElevationAmericans with Disabilities ActAmerican Red CrossAmerican Society of Civil EngineersAmerican Society for Testing and MaterialsAmerican Society of Civil Engineers’ Structural Engineers InstituteBase Flood ElevationBrick Industry AssociationBuilt-Up RoofComponents and CladdingConcrete Masonry UnitDesign Flood ElevationExterior Insulation Finish SystemsEmergency Operation CenterEthylene Propylene Diene MonomerFederal Emergency Management AgencyFlood Insurance Rate MapAcronymsA-1

FISFMAFMGFMRHMGPIBCICCICULPSMEPSMOBMWFRSNBCNEHRPNFIPNFPANSSAOSBPAPDMPMRPNPSBCSEAWSHMOSPFUBCFlood Insurance StudyFlood Mitigation AssistanceFactory Mutual GlobalFactory Mutual ResearchHazard Mitigation Grant ProgramInternational Building CodeInternational Code CouncilIntensive Care UnitLightning Protection SystemMolded Expanded PolystyreneMedical Office BuildingMain Wind-Force Resisting SystemNational Building CodeNational Earthquake Hazard Reduction ProgramNational Flood Insurance ProgramNational Fire Protection AssociationNational Storm Shelter AssociationOriented Strand BoardPublic AssistancePre-Disaster MitigationProtected Membrane RoofPrivate Non-ProfitStandard Building CodeStructural Engineers Association of WashingtonState Hazard Mitigation OfficerSprayed Polyurethane FoamUniform Building CodeA-2 Acronyms

Glossary of termsB100-year flood. See “base flood.”AAlluvial Fan. A fan-shaped deposit of alluvium formed by a stream where its velocity is abruptly decreased,as at the mouth of a ravine or at the foot of a mountain.Astragal. The center member of a double door, which is attached to the fixed or inactive doorpanel.BBase flood. The flood having a 1-percent chance of being equaled or exceeded in any givenyear, commonly referred to as the “100-year flood.” The base flood is the national standardused by the NFIP and all Federal agencies for the purposes of requiring the purchase of floodinsurance and regulating new development.Base flood elevation (BFE). The height of the base (1 percent or 100-year) flood in relation to aspecified datum, usually the National Geodetic Vertical Datum of 1929, or the North AmericanVertical Datum of 1988.Basic wind speed. A 3-second gust speed at 33 feet above the ground in Exposure C. (ExposureC is flat open terrain with scattered obstructions having heights generally less than 30 feet.)Note: Since 1995, ASCE 7 has used a 3-second peak gust measuring time. A 3-second peak gustis the maximum instantaneous speed with a duration of approximately 3 seconds. A 3-secondpeak gust speed could be associated with a given windstorm (e.g., a particular storm could havea 40-mph peak gust speed), or a 3-second peak gust speed could be associated with a designlevelevent (e.g., the basic wind speed prescribed in ASCE 7).glossary of termsB-1

Building, enclosed. A building that does not comply with the requirements for open or partiallyenclosed buildings.Building, open. A building having each wall at least 80 percent open. This condition is expressedby an equation in ASCE 7.Building, partially enclosed. A building that complies with both of the following conditions:1. The total area of openings in a wall that receives positive external pressure exceedsthe sum of the areas of openings in the balance of the building envelope (walls androof) by more than 10 percent.2. The total area of openings in a wall that receives positive external pressure exceeds 4square feet, or 1 percent of the area of that wall, whichever is smaller, and the percentageof openings in the balance of the building envelope does not exceed 20 percent.These conditions are expressed by equations in ASCE 7.Building, regularly shaped. A building having no unusual geometrical irregularity in spatial form.Building, simple diaphragm. An enclosed or partially enclosed building in which wind loadsare transmitted through floor and roof diaphragms to the vertical main wind-force resistingsystem.CComponents and cladding (C&C). Elements of the building envelope that do not qualify as part ofthe main wind-force resisting system.Coping. The cover piece on top of a wall exposed to the weather, usually made of metal, masonry,or stone, and sloped to carry off water.DDesign flood. The greater of the following two flood events: (1) the base flood, affecting thoseareas identified as special flood hazard areas on a community’s Flood Insurance Rate Map(FIRM); or (2) the flood corresponding to the area designated as a flood hazard area on acommunity’s flood hazard map or otherwise legally designated.Design flood elevation (DFE). The elevation of the design flood, including wave height, relative tothe datum specified on a community’s flood hazard map.Dry floodproofing. An adjustment, modification, or addition of a feature, or any combinationthereof, that eliminates or reduces the potential for flood damage by sealing walls and closingopenings to keep water from entering a building.B-2 Glossary of terms

EErodible soil. Soil subject to wearing away due to the effects of wind, water, or other geologicalprocesses during a flood or storm or long-term exposure.Escarpment. Also known as a scarp. With respect to topographic effects, a cliff or steep slopegenerally separating two levels or gently sloping areas.Exposure. The characteristics of the ground roughness and surface irregularities in the vicinityof a building. ASCE 7 defines three exposure categories—Exposures B, C, and D.Extratropical storm. A cyclonic storm that forms outside of the tropical zone. Extratropicalstorms may be large, often 1,500 miles (2,400 kilometers) in diameter, and usually contain acold front that extends toward the equator for hundreds of miles.FFederal Emergency Management Agency (FEMA). The Federal Emergency Management Agency isthe Federal agency which administers the National Flood Insurance Program (NFIP).Fetch. Distance over which wind acts on the water surface to generate waves.Flashing. Any piece of material, usually metal or plastic, installed to prevent water from penetratinga structure.Flood Insurance Rate Map (FIRM). The official map of a community on which FEMA has delineatedboth the special hazard areas, and the risk premium zones applicable to the community.Flood Insurance Study (FIS). An engineering study performed by FEMA to identify flood hazardareas, flood insurance risk zones, and other flood data in a community; used in the developmentof the FIRM.Floodplain. Any land area, including the watercourse, that is susceptible to partial or completeinundation by water, from any source.Floodplain management regulations. Zoning ordinances, subdivision regulations, building codes,or special-purpose ordinances that set flood-resistant standards for new construction, land use,and development.Flood profile. A graph of computed flood elevations at points located along a riverine waterway.A flood profile typically is available for a waterway that has Base Flood Elevations (BFEs) shownon the Flood Insurance Rate Map (FIRM). Flood profiles are usually found in the Flood InsuranceStudy (FIS) report.Glossary of termsB-3

Floodway. The channel and that portion of the floodplain that is to be reserved to convey thebase flood, without cumulatively increasing the water surface elevation more than a designatedheight.Floodway fringe. The area of the floodplain outside of the floodway, where floodwaters may beshallower and slower.Freeboard. A factor of safety, usually expressed in feet above a flood level, for purposes of floodplainmanagement. Freeboard also compensates for the many unknown factors that couldcontribute to flood heights greater than the height calculated for a selected size flood andfloodway conditions, such as wave action, constricting bridge openings, and the hydrologicaleffect of urbanization of the watershed. A freeboard of 1 to 3 feet is often applied to criticalfacilities.Frontal dune. Ridge or mound of unconsolidated sandy soil, extending continuously alongshorelandward of the sand beach and defined by relatively steep slopes abutting markedly flatter andlower regions on each side.GGlazing. Glass or a transparent or translucent plastic sheet used in windows, doors, andskylights.Glazing, impact-resistant. Glazing that has been shown, by an approved test method, to withstandthe impact of wind-borne missiles likely to be generated in wind-borne debris regionsduring design winds.HHurricane-prone regions. Areas vulnerable to hurricanes; in the United States and its territoriesdefined as:1. The U.S. Atlantic Ocean and Gulf of Mexico coasts, where the basic wind speed isgreater than 90 miles per hour.2. Hawaii, Puerto Rico, Guam, U.S. Virgin Islands, and American Samoa.Human intervention. The presence and active involvement of people necessary to enact or implementfloodproofing measures prior to the onset of flooding.Hydrodynamic load. Loads imposed by water flowing against and around an object or structure,including the impacts of debris and waves.B-4 Glossary of terms

Hydrostatic load. Load (pressure) imposed on an object or structure by a standing mass ofwater; the deeper the water, the greater the load or pressure against the object or structure.IImpact-resistant covering. A covering designed to protect glazing, which has been shown by anapproved test method to withstand the impact of wind-borne missiles likely to be generated inwind-borne debris regions during design winds.Importance factor, I. A factor that accounts for the degree of hazard to human life and damageto property. Importance factors are given in ASCE 7.LLowest floor. The lowest floor of the lowest enclosed area (including basement). An unfinishedor flood resistant enclosure, usable solely for parking of vehicles, building access, or storage, inan area other than a basement area, is not considered a building's lowest floor, provided thatthe enclosure is compliant with flood-resistant requirements.MMain wind-force resisting system. An assemblage of structural elements assigned to provide supportand stability for the overall structure. The system generally receives wind loading frommore than one surface.Mean roof height, (h). The average of the roof eave height and the height to the highest pointon the roof surface, except that, for roof angles of less than or equal to 10 degrees, the meanroof height shall be the roof eave height.Missiles. Debris that could become propelled into the wind stream.NNational Flood Insurance Program (NFIP). A Federal program to identify flood-prone areas nationwide,and make flood insurance available for properties in communities that participate in theprogram.Nor’easter. Nor’easters are non-tropical storms that typically occur in the eastern United States,any time between October and April, when moisture and cold air are plentiful. They areknown for dumping heavy amounts of rain and snow, producing hurricane-force winds, andcreating high surfs that cause severe beach erosion and coastal flooding. A nor’easter is namedfor the winds that blow in from the northeast and drive the storm up the east coast along theGulf Stream, a band of warm water that lies off the Atlantic Coast.Glossary of termsB-5

OOpenings. Apertures or holes in the building envelope that allow air to flow through the buildingenvelope. A door that is intended to be in the closed position during a windstorm would not beconsidered an opening. Glazed openings are also not typically considered openings. However,if the building is located in a wind-borne debris region and the glazing is not impact-resistant orprotected with an impact-resistant covering, the glazing is considered an opening.RRacking. Lateral deflection of a structure resulting from external forces, such as wind or lateralground movement in an earthquake.Ridge. With respect to topographic effects, an elongated crest of a hill characterized by strongrelief in two directions.SScour. Removal of soil or fill material by the flow of floodwaters. The term is frequently used todescribe storm-induced, localized erosion around pilings at building corners and other foundationsupports where the obstruction of flow increases turbulence.Seiche. A wave that oscillates in lakes, bays, or gulfs from a few minutes to a few hours as a resultof seismic or atmospheric disturbances.Sheetflow. Rainfall runoff that flows over relatively flat land without concentrating into streamsor channels.Stillwater elevation. The elevation that the surface of coastal flood waters would assume in theabsence of waves, referenced to a datum.Storm surge. Rise in the water surface above normal water level on the open coast due to thelong-term action of wind and atmospheric pressure on the water surface.Substantial damage. Damage of any origin sustained by a structure, whereby the cost of restoringthe structure to its pre-damage condition equals or exceeds 50 percent of the market valueof the structure before the damage occurred (or smaller percentage if established by the authorityhaving jurisdiction). Structures that are determined to be substantially damaged areconsidered to be substantial improvements, regardless of the actual repair work performed.Substantial improvement. Any reconstruction, rehabilitation, addition, or other improvement ofa structure, the cost of which equals or exceeds 50 percent of the market value of the structure(or smaller percentage if established by the authority having jurisdiction) before the start ofthe improvement.B-6 Glossary of terms

TTsunami. An unusually large sea wave produced by submarine earth movement or a volcaniceruption.WWave runup. Rush of wave water up a slope or structure. The additional height reached by wavesabove the stillwater elevation.Wet floodproofing. Permanent or contingent measures and construction techniques, applied toa structure or its contents, that prevent or provide resistance to damage from flooding whileallowing floodwaters to enter the structure. Generally, this includes properly anchoring thestructure, using flood-resistant materials below the BFE, protection of mechanical and utilityequipment, and the use of openings or breakaway walls.Wind-borne debris regions. Areas within hurricane-prone regions located:1. Within 1 mile of the coastal mean high water line where the basic wind speed is equalto or greater than 110 mph and in Hawaii.2. In areas where the basic wind speed is equal to or greater than 120 mph.Glossary of termsB-7

FEMA Mitigation ProgramscFederal funding for mitigation is availableon a regular basis for pre-disaster mitigationactivities and as federal assistancefollowing a presidential disaster declaration.Table 1 provides a side-by-side comparison ofavailable funding programs administered byFEMA. Although each program is constrainedin a number of ways, as explained below, thefollowing sources of federal funding may beavailable for mitigation projects for criticalfacilities:Many other federal and state fundingsources may be available to supportplanning and construction (or upgrades) ofsome critical facilities, but this manual doesnot identify or list such sources. Owners,planners, and community leaders areencouraged to contact appropriate stateagencies to learn more.m Section 406 Public Assistance (PA) is a post-disaster programestablished under Section 406 of the Stafford Act—it isjointly administered by FEMA and individual states. As partof the reimbursements made to restore damaged publicfacilities and certain private non-profit (PNP) facilities, publicassistance funds may be made available for cost-effectivemitigation measures undertaken as part of the recovery. Theamount of Section 406 Mitigation funds made available inany given disaster is not computed by a formula, but is basedon a project-by-project evaluation of the feasibility and costeffectivenessof mitigation measures.m Section 404 Hazard Mitigation Grant Program (HMGP) is a postdisasterprogram established under Section 404 of the StaffordAct. It offers funding to states, communities, and other eligibleFEMA Mitigation ProgramsC-1

grant recipients to invest in long-term measures that willreduce vulnerability to future natural hazards. The states havea strong role in administering HMGP, with FEMA providingoversight. Contact the State Hazard Mitigation Officer(SHMO) for state-specific information. General guidelines andresources for this program can be found on the FEMA website(www.fema.gov/fima/hmgp).m Pre-Disaster Mitigation (PDM), established under Section 203of the Stafford Act, is a nationally competitive grant programdesigned to assist states and communities to develop mitigationplans and implement mitigation projects. PDM funds areappropriated annually. FEMA convenes national panels toevaluate eligible applications. Applications are submittedby states following the state selection process. Communitiesshould contact the SHMO for state-specific PDM procedures.PDM program guidance and other information can be foundon the FEMA website (www.fema.gov/government/grant/pdm/index.shtm).m Flood Mitigation Assistance (FMA) is a grant program funded bythe National Flood Insurance Program (NFIP) and focusedon buildings that are insured by the NFIP, with particularattention to buildings that have received multiple claimpayments. As with the HMGP, FMA is state-administered,and information and assistance is available from the SHMO.General guidelines and resources for this program can befound on the FEMA website (www.fema.gov/government/grant/fma/index.shtm).As part of the Hurricane Katrina recovery in Mississippi and Louisiana, FEMA initiated a postdisasterPartnering Mitigation Programs initiative to combine funding from Section 406 andSection 404 where possible. Section 406 mainly funds the repair and restoration of stormdamage; thus, some building elements may remain exposed to future damage. The initiativefosters a cooperative approach to making decisions to use both PA and HMGP funds toaccomplish recovery as well as mitigation of facilities as whole buildings in a seamless fashion.C-2 FEMA Mitigation Programs

Table 1: Side-by-Side of FEMA ProgramsItem PA (406) HMGP (404) PDM (203) FMAEligibleApplicants andSub-applicantsfor ProjectGrantsState and localgovernments; PNPorganizations orinstitutions that ownor operate a PNPfacility (as definedin regulation);Indian tribes orauthorized tribalorganizationsand AlaskaNative villages ororganizations, butnot Alaska nativecorporations withownership vested inprivate individuals.State and localgovernments; PNPorganizations orinstitutions that ownor operate a PNPfacility (as definedin regulation);Indian tribes orauthorized tribalorganizationsand AlaskaNative villages ororganizations, butnot Alaska nativecorporations withownership vested inprivate individuals.State-level agencies;local governments,Indian tribes,authorized Indiantribal organizations,and AlaskaNative villages;public collegesand universities;tribal colleges anduniversities. PNPorganizations andprivate collegesand universitiesare not eligiblesub-applicants, buta relevant stateagency or localgovernment mayapply on theirbehalf.State agencies,NFIP-participatingcommunities(have zoning andbuilding codejurisdiction), andlocal authoritiesdesignated to planand implementprojects.EligibleActivitiesBasic assistanceto repair thedamaged elementsof public facilitiesand infrastructure.Eligible mitigationactivities are onlythose that protectagainst directphysical damagesto structures,building, andcontents.Eligible activitiesinclude structuraland nonstructuralmitigation measuresthat are feasibleand cost-effective.Projects may countbenefits in termsof building andcontents damages,displacement costs,loss of function,and casualties andloss of life.Eligible measuresmust be costeffectiveanddesigned to reduceinjuries, loss oflife, and damageand destruction ofproperty, includingdamage to criticalservices andfacilities underthe jurisdiction ofthe states or localgovernments.Cost Share75 percent federal75 percent federal75 percent federal75 percent federal25 percent nonfederal25 percent nonfederal25 percent nonfederal25 percent nonfederalSmall, impoverishedcommunities maybe eligible for 90percent federalshare.FEMA Mitigation ProgramsC-3

Table 1: Side-by-Side of FEMA Programs (continued)Item PA (406) HMGP (404) PDM (203) FMAFundingSourceThe DisasterRelief Fund after apresidential disasterdeclaration; publicassistance mustbe authorizedspecifically as partof the disasterdeclaration.The DisasterRelief Fund after apresidential disasterdeclaration; HMGPmust be authorizedspecifically as partof the disasterdeclaration.An annualappropriation byCongress.Annualappropriationby Congress, bytransfer of incomefrom the NationalFlood InsuranceFund.PlanningRequirementFor categories C-G assistance, astate must have anapproved mitigationplan.For disastersdeclared after11/1/04, state andlocal governmentsmust have anapproved mitigationplan.State and localmitigation plansmust be adoptedand approved byFEMA prior to thebeginning of theselection process,as a preconditionfor receiving projectgrants.Recipient musthave adopted amitigation planapproved by FEMAprior to receipt ofgrant funds.ApplicationDeadlineProject worksheetsusually are dueno later than 60days after a formalbriefing presentedby FEMA and thestate (extensionsmay be grantedin unusualcircumstances).Applications must besubmitted to FEMAwithin 12 monthsof the disasterdeclaration date(extensions may begranted in unusualcircumstances).Varies by year;contact state agencyfor additionalinformation.Usually late spring;specific date variesby year, contactstate agencyfor additionalinformation.Public Assistance (Section 406)Following a presidential disaster declaration, the PA programprovides assistance for debris removal, emergency protective measures,and permanent restoration of publicly owned infrastructure.Eligible recipients of this assistance include state and local governments,Indian tribes or authorized tribal organizations, andAlaska Native villages. Certain PNP organizations may also receiveassistance. Eligible PNPs include educational, utility, irrigation,emergency, medical, rehabilitation, temporary or permanent cus-C-4 FEMA Mitigation Programs

todial care facilities (including those for the aged and disabled),and other PNP facilities that provide essential services of a governmentalnature to the general public. Certain PNPs that provide“critical services” may apply directly to FEMA, including PNPsthat provide power, sewer, wastewater treatment, communications,emergency medical care, and water (including water provided byan irrigation organization or facility).As soon as practical after the declaration, the state, assisted byFEMA, conducts Applicants’ Briefings for state, local, and PNPofficials, to inform them of the assistance available and the applicationprocedure. A request for public assistance must be filedwith the state within 30 days after an area is designated eligible forassistance.Following the Applicants’ Briefing, a kickoff meeting is conductedwith each eligible grant recipient, where specific damagesare discussed, needs assessed, and a plan of action put in place.A combined federal/state/local team proceeds with project formulation—theprocess of documenting eligible facilities anddetermining the cost for fixing the identified eligible damages.The team prepares a project worksheet foreach project. Eligible projects fall into thefollowing categories:Category A: Debris removalCategory B: Emergency protective measuresCategory C: Roads and bridgesCategory D: Water control facilitiesCategory E: Public buildings and contentsCategory F: Public utilitiesCategory G: Parks, recreational, and otherFEMA reviews and approves the project worksheets and obligatesthe federal share of the costs to the state, which, in turn, disbursesthe funds to local applicants. The federal share is not less than 75percent of the eligible project costs (except in extraordinary circumstances,when some costs are eligible for 90 or 100 percentreimbursement).The facility owner must pay for all coststhat are not eligible for Section 406reimbursement. The non-federal sharecan be a combination of cash and in-kindresources. Federal funding from othersources cannot be used as matching funds,with the exception of federal fundingprovided to states under the CommunityDevelopment Block Grant program fromthe Department of Housing and UrbanDevelopment.FEMA Mitigation ProgramsC-5

Damaged buildings that are in a mappedfloodplain and insured by NFIP may haveaccess to an insurance payment to helpcover the cost of mitigation, provided thedamage caused by flooding is determinedto be “substantial damage.” A buildingis substantially damaged when the valueof the work required to repair it to its predamagedcondition equals or exceeds50 percent of the market value of thebuilding. In these cases, increased costof compliance coverage in NFIP floodinsurance policies provides to ownersup to $30,000 to bring the building intocompliance with floodplain managementrequirements. This payment may be usedas part of the non-federal match of grantfundedmitigation projects designed toaddress flood hazards.Section 406 provides FEMA with the authorityto fund mitigation measures in conjunctionwith the repair of damaged facilities involvingpermanent restorative work (CategoriesC, D, E, F, and G projects). The mitigationmeasures must be related to the eligible disasterdamages and must directly reduce thepotential of future, similar damages to the eligiblefacility. In providing this discretionaryauthority, Congress recognized that the postdisasterperiod offers unique opportunitiesto prevent the recurrence of similar damagein future disasters. These measures are additionalto any other measures undertaken forthe purpose of compliance with applicablecodes and standards, although such compliance,itself, could be considered a form ofmitigation. The following are examples of thetypes of mitigation required for compliancewith building codes that are eligible underSection 406:m Improved building materials such as impact-resistant windowsor flood-resistant materialsm Anchoring of rooftop equipmentm Improved installation methods or techniquesm New or higher elevation (for flood-prone facilities)Owners of eligible public facilities often wish to repair and restorea damaged facility in ways that exceed the current buildingcode requirements, in order to further reduce or eliminate futuredamage. Where it can be demonstrated that doing so is cost-effective,the added costs of such actions are eligible under FEMAPolicy 9526.1 governing the implementation of the Section 406program. Unfortunately, this approach rarely meets all the identifiedmitigation needs, because the funding can be used only forthe damaged elements—mitigation of vulnerable but undamagedelements is not allowed. For example, a police station with somedamaged windows can use Section 406 funds to replace the dam-C-6 FEMA Mitigation Programs

aged windows with impact-resistant windows, but cannot replaceundamaged windows. To address this limitation, facility ownersshould seek other sources of mitigation funding, such as theHazard Mitigation Grant Program described below.All mitigation activities funded with Section 406 funds must becost-effective. To facilitate recovery, FEMA can apply one of severaltests to determine cost-effectiveness:m Measures may cost to up to 15 percent of the total eligible costof the eligible repair work on a particular project.m Certain pre-approved mitigation measures identified in FEMApolicies will be determined to be cost-effective, as long as thecost of the mitigation measure does not exceed 100 percent ofthe eligible cost of the repair project.m For measures that do not meet the first or second test, theproject applicant must demonstrate cost-effectiveness usingan acceptable benefit/cost analysis. FEMA developed benefit/cost models that are specific to hurricanes, coastal flooding,riverine flooding, earthquakes, and tornadoes.Hazard Mitigation Grant Program (Section 404)Section 404, HMGP, is FEMA’s primary hazard mitigation programto help implement long-term mitigation measures following majordisaster declarations. Under HMGP, each state manages its ownprogram, and eligible participants include state and local governments,tribes, and PNP organizations. The program funds up to75 percent of the costs of individual FEMA-approved projects. Thetotal amount of funding made available after specific disasters dependson several variables.HMGP funds have been used for many types of projects, includingthe following:m Wind-resistant Retrofits. Existing facilities that were built beforecurrent code requirements may be eligible to be retrofitted toresist high winds. For any given building, applicable measuresare identified by conducting an evaluation of the building.FEMA Mitigation ProgramsC-7

Critical facilities have been retrofitted with shutters forwindows and doors, and anchoring of architectural featuresand rooftop equipment.m Floodproof Retrofits. Depending upon the nature of theflood risk, elevating an existing flood-prone structure orincorporating dry floodproofing techniques may be the mostpractical approach to meet NFIP requirements and thoseadministered by states and local governments.m Code Upgrades. Certain measures intended to provide a levelof protection that exceeds the minimum requirements of theapplicable building code may be eligible. This approach tomitigation is especially applicable for critical facilities thatserve vital post-disaster functions.m Relocation. In some cases, it may be viable to physically move astructure to a new location outside of high-risk flood hazardareas. Relocated buildings must be placed on a site locatedoutside of the 100-year floodplain and any regulatory erosionzones, in conformance with all applicable state or local landuse regulations.m Acquisition and Demolition. The community purchases the flooddamagedproperty and demolishes the structure. The acquiredproperty must be maintained as open space in perpetuity.Pre-Disaster Mitigation (Section 203)PDM provides funds to state and local governments for hazardmitigation planning and the implementation of cost-effectivemitigation projects unrelated to a specific disaster. PDM isadministered directly by FEMA. Eligible applicants includestates, tribes, territories, and local governments (PNPs can applyif sponsored by an eligible applicant). Grants are awarded ona nationwide competitive basis and without a formula-basedallocation.Similar to HMGP, PDM has funded numerous projects that improvewind- and flood-resistance of critical facilities such asemergency operations centers, hospitals, fire stations, police sta-C-8 FEMA Mitigation Programs

tions, and wastewater treatment plants.Specific measures include strengthening exteriorwalls, anchoring rooftop equipment,installing shutters, and elevation of facilitiesor equipment above the 100-year flood elevation.Other types of projects may be eligible,provided they meet the program requirementsand are cost-effective. Each year, FEMAissues PDM program guidance with specificcriteria.Cost Share for Small, ImpoverishedCommunitiesPDM grants awarded to small,impoverished communities may receivea federal cost share of up to 90 percentof eligible costs. To qualify, a communitymust meet several eligibility criteria relatedto population, average annual income,unemployment rate, and other conditions.Flood Mitigation Assistance ProgramFMA is designed to fund mitigation projects that are cost-effectiveand in the best interest of NFIP. Funds are provided annually fromincome collected from flood insurance policyholders. Each statemanages its own program. Eligible grant recipients must have aFEMA-approved mitigation plan. Eligible recipients include communitiesthat have land use authority and participate in the NFIP,certain other local authorities, and state agencies. The programfunds up to 75 percent of certain eligible costs for measures thatreduce or eliminate flood damage to buildings that are insured bythe NFIP, including buildings and facilities owned by public agenciesand PNP entities.Eligible activities under the FMA program include acquisition,increased elevation, relocation, demolition, floodproofing, andactivities that bring nonresidential structures into compliancewith minimum NFIP requirements and state and local codes, andminor physical activities such as drainage improvements. As withHMGP, if an NFIP-insured building is damaged by a flood andfound to be eligible for the increased cost of compliance claimpayment to bring the building into compliance, the payment canbe used as part of the required non-federal match for FMA grants.FEMA Mitigation ProgramsC-9