Technical Manual: Conduits through Embankment Dams (FEMA 484)

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Conduits through Embankment DamsAvailable data may not be reviewed and evaluated prior to the inspection,depending on the inspector’s familiarity with the conduit. Inspections may bescheduled regularly or performed in conjunction with other routine tasks.• Special.—A special inspection is conducted when a unique opportunity exists forinspection. For example, if low water conditions exist in a reservoir exposing anormally inundated structure, a special inspection may be arranged.• Emergency.—An emergency inspection is performed when an immediate damsafety concern is present or in the event of an unusual or potentially adversecondition (i.e., immediately following an earthquake).The actual terms and meanings used to define the types of inspection may varybetween dam safety organizations and embankment dam owners.The operating personnel responsible for daily operation and maintenance of thefacility should also participate as inspection team members. Where applicable, wateruser organization representatives should also participate in the inspection.Additionally, the applicable State water resource agency may need to be advised fortheir possible participation in the inspection.To the extent possible, inspections should be scheduled in different seasons. Thiswill enable the structure or facility to be examined under differing reservoir levels,water delivery, and site conditions.Before beginning inspection of a facility, the inspection team should discuss theorder in which features are to be examined, to accommodate operations, as well as toensure that time for the inspection team is appropriately allotted. In addition, theteam should conduct a job hazard analysis (JHA) prior to the inspection, wherebyprocedures and equipment necessary to minimize or avoid potential safety and healthhazards are discussed. Of primary importance is the need for detailed clearance(particularly if there are confined spaces), and lockout or “tag-out” procedures whenaccessing areas affected by equipment or gate/valve operations. For guidance onpreparing a JHA, see section 9.4.9.2 Factors influencing scheduling of inspectionsScheduling of periodic conduit inspections may be influenced by (Reclamation, 1988,p. III-7):196• Sufficient notice .—Embankment dam owners and operators may need sufficienttime to make necessary arrangements, such as preinspections associated withlockout/tagout and confined space entry, or special equipment or approval for
Chapter 9—Inspection and Assessment of Conduit-Related Problemsunwatering conduits, terminal structures, or pools. This process could requireseveral weeks or months, depending on the facility.• Scheduling access.—Access for the inspection should be scheduled when most orall of the major components of the conduit can be examined. Some features,such as intake structures and upstream conduits, are usually submerged and notaccessible. Downstream conduits and terminal structures may or may not beable to be unwatered and made accessible for inspection. The embankmentdam owner or operator may be requested to provide notification whenreservoir conditions permit or when the reservoir can be drawn down to allowthe inspection to be performed.If the feature to be inspected is normally inundated and inaccessible, certainfactors (Reclamation, 1985, p. 4) should be considered in determining theextent and frequency for inspection, such as:1. Results of previous “hands on” inspection or evidence from theinspection of the normally accessible portions of the feature. Inspectionof the normally accessible portion of a feature may provide informationon the probable condition of the inaccessible portion. This informationmay include:a. Condition of the feature.—Cracking, joint separation, or significantdeterioration.b. Condition of the embankment dam and foundation.—Excessivepostconstruction settlement or alignment distortion of thedownstream conduit; excessive embankment dam settlement or theexistence of sinkholes on the upstream face along the alignment ofthe conduit.c. Observed seepage.—Seepage or wet areas observed at the downstreamtoe of the embankment dam.d. Flow conditions.—Changes in the discharge capacity of the conduit.e. Damage and deterioration.—Damage or deterioration of gates/valvesand metalwork..f. Water quality.—Water quality known to be detrimental to concrete,conduit linings, or waterstops. Excessive amounts of sand or othermaterial transported by the discharge.197
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Technical Manual:Conduits throughEm
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PrefaceTens of thousands of conduit
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Prefacecondition. The hazard classi
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PrefaceLakeLine MagazineMaryland Da
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Conduits through Embankment Dams11.
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Contents23 Precast concrete pipe be
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Contents81 On first filling, a high
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Contents117 This conduit was severe
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Contents158 An example of a histori
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ContentsFigures in the AppendicesNo
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ContentsB-33 Aerial view of Como Da
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ContentsB-81 Cross section of Wiste
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ContentsMASW, multichannel analysis
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Symbolsc, cohesionE', modulus of so
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ContentsD 3350D 4221D 4253D 4254D 4
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IntroductionConduits convey water f
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IntroductionFigure 3.—A 15-inch d
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Introductionunstable. When seepage
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IntroductionAn embankment dam with
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A vortex may form at the location w
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IntroductionWater from the reservoi
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IntroductionFlowing water from the
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IntroductionThe process of dislodgi
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Introductionbe observable at the su
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IntroductionFigure 11.—Example of
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Introductionwhere conduits were ass
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Introduction• Conduits within lev
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IntroductionFigure 12.—An example
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Introductionmore recent practiced h
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IntroductionThe “best practices
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Chapter 1GeneralConduits have been
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Chapter 1—GeneralFigure 14.—Ant
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Chapter 1—GeneralFigure 17.—Fai
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Chapter 1—Generalmeans the condui
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Chapter 1—Generalfacilitate futur
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Chapter 2Conduit MaterialsVarious m
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Chapter 2—Conduit MaterialsFigure
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Chapter 2—Conduit Materials• Co
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Chapter 2—Conduit MaterialsSteel
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Chapter 2—Conduit Materials2.3.2
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Chapter 3Hydraulic Design of Condui
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Chapter 3—Hydraulic Design of Con
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Chapter 4Structural Design of Condu
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Chapter 4—Structural Design of Co
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Chapter 5Foundation and Embankment
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Chapter 5—Foundation and Embankme
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Chapter 6Filter ZonesZones of desig
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Chapter 6—Filter Zonesseepage or
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Chapter 6—Filter ZonesFigure 87.
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Chapter 6—Filter Zones3. Upstream
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Chapter 6—Filter Zonesbedrock sur
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Page 195 and 196: Chapter 7Potential Failure Modes As
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Page 215 and 216: Chapter 8Potential Defects Associat
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Chapter 10—Evaluation by Geophysi
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Chapter 11Appropriate Emergency Act
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Chapter 11—Appropriate Emergency
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Table 11.2.—Potential problems an
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Chapter 12Renovation of ConduitsThe
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Chapter 12—Renovation of Conduits
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Chapter 13Replacement of ConduitsGe
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Chapter 13—Replacement of Conduit
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Chapter 14Repair and Abandonment of
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Chapter 14—Repair and Abandonment
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ReferencesThe following references
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ReferencesBureau of Reclamation, De
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ReferencesCooper, Chuck, E. Wesley
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ReferencesJacobsen, S., “Buckling
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ReferencesNatural Resources Conserv
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ReferencesU.S. Army Corps of Engine
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ReferencesWooten, R. Lee, Peter S.
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Additional ReadingThe following ref
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Additional ReadingCarter, Brent H.,
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Additional ReadingJohnson, Brian, J
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Additional ReadingNatural Resources
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Additional ReadingU.S. Army Corps o
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Additional ReadingVan Aller, Hal, R
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GlossaryThe terms defined in this g
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Glossary• Backward erosion piping
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GlossaryCathodic protection system
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GlossaryConsequences (FEMA, 2004):
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Glossarymalfunction or abnormality
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GlossaryDrawdown (FEMA, 2004): The
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GlossaryFailure mode (FEMA, 2004):
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GlossaryGate chamber: An outlet wor
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GlossaryImpervious: Not permeable;
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GlossaryLeakage (FEMA, 2004): Uncon
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GlossaryOpen cut: An excavation thr
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GlossaryPolyvinyl chloride (PVC): A
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GlossaryResistivity: A measure of t
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GlossarySettlement (FEMA, 2004): Th
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GlossaryStandard Proctor compaction
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GlossaryThermoset (ASTM F 412, 2001
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GlossaryReferencesAmerican Concrete
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IndexAAbandonment of conduits, 225,
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IndexCompaction of backfill, 6, 10,
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IndexDDamembankment, 113-130, 333-3
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IndexExisting conduit, 23, 31, 45-5
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IndexHydraulic fracture, 4-11, 17,
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IndexMechanical caliper, 246Metal c
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IndexPressure flow, see Conduit, pr
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IndexSliplining, 39, 45-47, 51, 164
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IndexUUltrasonic pulse-echo, 245, 2
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Appendix AHistory of Antiseep Colla
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Appendix A—History of Antiseep Co
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Appendix BCase HistoriesIndexDam Lo
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Appendix B—Case HistoriesDam Loca
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Appendix B—Case HistoriesProject
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Appendix B—Case HistoriesFigure B
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Appendix B—Case Historiesproject,
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Appendix B—Case Historieswatersto
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Appendix B—Case HistoriesLessons
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Appendix B—Case HistoriesThe cond
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Appendix B—Case Historiesroadway.
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Appendix B—Case Historiesentire c
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Appendix B—Case Historieshauled i
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Appendix B—Case Historiescoal tar
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Appendix B—Case Historieshistory
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Appendix B—Case Historiesarea, a
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Appendix B—Case Historiespipe. Du
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Appendix B—Case Historiesinvert o
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Appendix B—Case Historiesof sever
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Appendix B—Case HistoriesThe down
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Appendix B—Case Historieshose and
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Appendix B—Case HistoriesADownstr
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Technical Manual: Conduits through Embankment Dams (FEMA 484)

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