Potomac Waterfront Flood Mitigation Study - City of Alexandria

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TABLE OF CONTENTS 6.1.2 Assumptions ...............................................................................6-5 6.1.3 Potential Impacts.........................................................................6-7 6.1.4 Permitting/Approval Requirements.............................................6-8 6.1.5 BCA and Results.......................................................................6-10 6.2 Elevated Walkway................................................................................6-10 6.2.1 Description of Alternative.........................................................6-11 6.2.2 Assumptions .............................................................................6-16 6.2.3 Potential Impacts.......................................................................6-16 6.2.4 Permitting/Approval Requirements...........................................6-17 6.2.5 BCA and Results.......................................................................6-19 6.3 Jones Point Berm..................................................................................6-19 6.3.1 Description of Alternative.........................................................6-19 6.3.2 Assumptions .............................................................................6-23 6.3.3 Potential Impacts.......................................................................6-23 6.3.4 Permitting/Approval Requirements...........................................6-23 6.3.5 BCA and Results.......................................................................6-25 6.4 Improve Roadway Drainage .................................................................6-25 6.4.1 Description of Alternative.........................................................6-26 6.4.2 Assumptions .............................................................................6-26 6.4.3 Potential Impacts.......................................................................6-26 6.4.4 Permitting/Approval Requirements...........................................6-28 6.4.5 BCA and Results.......................................................................6-29 6.5 Acquire Properties ................................................................................6-30 6.5.1 Assumptions .............................................................................6-30 6.5.2 Potential Impacts.......................................................................6-30 6.5.3 Permitting/Approval Requirements...........................................6-30 6.5.4 Applicability of Acquisition/Benefit-Cost Analysis..................6-31 6.6 Floodproofing.......................................................................................6-33 6.6.1 Assumptions .............................................................................6-33 6.6.2 Potential Impacts.......................................................................6-34 6.6.3 Permitting/Approval Requirements...........................................6-34 6.6.4 Floodproofing Applicability/Benefit-Cost Analysis..................6-35 6.6.5 Floodproofing Applicability for Repetitive Loss Properties......6-45 SECTION SEVEN: RECOMMENDATIONS................................................................................................. 7-1 7.1 Overview of Recommendations..............................................................7-1 7.2 King Street..............................................................................................7-2 7.3 Waterfront Commercial ..........................................................................7-8 7.4 North Union............................................................................................7-9 7.5 Jones Point..............................................................................................7-9 7.6 Floodwall................................................................................................7-9 7.7 Repetitive Loss Properties ....................................................................7-12 7.8 Nonstructural Flood Mitigation Measures ............................................7-13 7.9 Additional Recommendations...............................................................7-14 7.10 Potential Federal Funding Options........................................................7-15 7.11 Conclusions ..........................................................................................7-15 SECTION EIGHT: REFERENCES ............................................................................................................... 8-1 28-JUL-10\\ ii
TABLE OF CONTENTS TABLES Table 2-1: Return Periods of Studied Flood Events ...................................................................2-1 Table 2-2: Summary of All Flood Mitigation Alternatives Considered......................................2-4 Table 2-3: Flood Mitigation Measure Final Rankings................................................................2-7 Table 3-1: Structures Recommended for Elevation of Contents...............................................3-13 Table 4-1: Repetitive Loss Properties within Study Area...........................................................4-8 Table 5-1: Estimated Loss of Business Time .............................................................................5-3 Table 5-2: Expected Annual Probabilities..................................................................................5-4 Table 5-3: Cultural Resource Approval Relative Schedule, Level of Effort, and Cost...............5-7 Table 6-1: Comparison of Potential Floodwall Layout Options.................................................6-2 Table 6-2: Floodwall Discharges and Volumes..........................................................................6-5 Table 6-3: Floodwall Benefit-Cost Ratio .................................................................................6-10 Table 6-4: Elevated Walkway Discharges and Volumes..........................................................6-15 Table 6-5: Elevated Walkway Benefit-Cost Ratio....................................................................6-19 Table 6-6: Berm Benefit-Cost Ratio.........................................................................................6-25 Table 6-7: Acquisition for Jones Point Benefit-Cost Results ...................................................6-32 Table 6-8: Acquisition for King Street Benefit-Cost Results ...................................................6-32 Table 6-9: Acquisition for Waterfront Commercial Benefit-Cost Results................................6-33 Table 6-10: Acquisition for North Union Benefit-Cost Results................................................6-33 Table 6-11: Estimated Costs for Various Floodproofing Methods ...........................................6-35 Table 6-12: Floodproofing Options for Jones Point: 17 Residential Structures........................6-36 Table 6-13: Cost Ratio for Jones Point: 17 Residential Structures ...........................................6-36 Table 6-14: Floodproofing Options for King Street: 23 Commercial Structures ......................6-38 Table 6-15: Benefit Cost Ratio for King Street: 23 Commercial Structures.............................6-38 Table 6-16: Floodproofing Options for King Street: 6 Residential Structures..........................6-39 Table 6-17: Benefit Cost Ratio King Street: 6 Residential Structures ......................................6-39 Table 6-18: Floodproofing Options for Waterfront Commercial: 22 Commercial Structures ..6-41 Table 6-19: Benefit Cost Ratio for Waterfront Commercial: 22 Commercial Structures .........6-43 Table 6-20: Dry Floodproofing Options for North Union: 37 Residential Structures...............6-43 Table 6-21: Benefit Cost Ratio for North Union: 37 Residential Structures.............................6-45 Table 6-22: Summary of Floodproofing Applicability for Repetitive Loss Properties .............6-45 Table 7-1: Applicability of Flood Mitigation Measures .............................................................7-1 28-JUL-10\\ iii
Page 2 and 3: F I N A L R E P O R T POTOMAC RIVER
Page 6 and 7: TABLE OF CONTENTS FIGURES Figure 1-
Page 8 and 9: ac acre A/E Architectural/Engineeri
Page 10 and 11: TES Transportation and Environmenta
Page 12 and 13: SECTION ONE: INTRODUCTION 1.1 POTOM
Page 14 and 15: Introduction Factory and Strand Str
Page 16 and 17: Refinement of Mitigation Measures S
Page 18 and 19: 8.8 ft Figure 2-2: Flood Levels Stu
Page 20 and 21: Refinement of Mitigation Measures T
Page 22 and 23: Refinement of Mitigation Measures s
Page 24 and 25: Overview of Flood Mitigation Measur
Page 26 and 27: 3.1.3 Floodproofing Overview of Flo
Page 28 and 29: FLOOD ELEVATION BASE FLOW Overview
Page 40 and 41: E LURAY AV E GLENDALE AV EARL ST N
Page 42 and 43: N ALFRED ST MUIRS CT S COLUMBUS ST
Page 44 and 45: Technical Analyses Support resource
Page 46 and 47: Table 4-1: Repetitive Loss Properti
Page 48 and 49: Technical Analyses Support climate
Page 50 and 51: 5.2 CALCULATION OF PROJECT BENEFITS
Page 52 and 53: Economic Valuation (Benefit-Cost An
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Economic Valuation (Benefit-Cost An
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6.1 FLOODWALL Structural Mitigation
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Structural Mitigation Measure Conce
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6.1.3 Potential Impacts Structural
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VDEQ Section 401 Certification VDE
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6.2.1 Description of Alternative St
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CLIENT PROJ RAMSAY AL SWIFTS AL S L
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6.2.4 Permitting/Approval Requireme
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6.2.5 BCA and Results Structural Mi
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6.3.2 Assumptions Structural Mitiga
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CLIENT PROJ REVISION NO SCALE WALES
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Site Plan Approval Structural Mitig
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North Union Structural Mitigation M
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CLIENT PROJ REVISION NO SCALE S ROY
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King Street Residential Structural
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Waterfront Commercial Structural Mi
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7.2 KING STREET Elevated Walkway Re
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Figure 7-2: Elevated Walkway at Wat
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Recommendations The elevated walkwa
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King/Strand Street Intersection Roa
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Figure 7-6: Floodwall behind Torped
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7.7 REPETITIVE LOSS PROPERTIES Reco
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Recommendations (USBC) and Internat
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SECTION EIGHT: REFERENCES Access Fl
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References Huber Technology, 2009.
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Appendix A Initial Ranking of Poten
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Appendix B Ordinance and Sandbag In
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Exhibit 1-2. Sample ordinance from
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5. The necessity to the facility of
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Appendix C Non-Prioritized Measures
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Figure 1: Duckbill Check Valve A ty
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Relocate external electrical boxes
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Last, Hurricane Preparedness inform
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Potomac River Waterfront Flood Miti
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Figure A1-12 Exhibit 2: Field Visit
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Exhibit 2: Field Visit Summary - Ju
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Fig A11-1 Exhibit 2: Field Visit Su
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Figure A18-1 Exhibit 2: Field Visi
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Figure 21-3 Exhibit 2: Field Visit
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Figure 2: Screen shot from NOAA Atl
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Potomac River Waterfront Flood Miti
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38 40 38 4 6 40 34 28 14 30 30 40 4
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46 44 38 44 42 40 42 44 44 36 22 36
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48 44 38 36 38 18 46 42 38 42 26 22
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CLIENT PROJ REVISION NO SCALE City
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Table 4: Detailed cost estimate for
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Exhibit 3: Various Elevated Walkway
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Exhibit 4-2: Elevated Walkway - Kin
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Appendix H Berm
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Roadway Drainage Additional Data Ta
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Appendix J Property Acquisition
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Appraisals Based on data from Appra
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Exhibit 2. Total Other Costs for Pr
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Table 4: North Union Acquisition Co
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Appendix K Floodproofing
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Exhibit 2. Window Replacement Costs
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Elevate or relocate the electric pa
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Overview Potential Federal Funding
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Table 1. HMA Funding Options by Pro
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Hazard Mitigation Assistance The De
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program comparisons (continued) ELI
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program information GovDelivery Not
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