LOUISIANA COASTAL PROTECTION AND RESTORATION FINAL TECHNICAL REPORT STRUCTURAL PLAN COMPONENT APPENDIX June 2009 U. S. Army Corps of Engineers New Orleans District Mississippi Valley Division Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Table of Contents PURPOSE ....................................................................................................................................................................1 INTRODUCTION .......................................................................................................................................................1 Three-Tiered Screening Process ................................................................................................. 2 Organization of This Appendix .................................................................................................. 3 PLANNING UNIT 1....................................................................................................................................................5 Tier 1 – Initial Screening of Structural Alignments.................................................................... 5 Cost Considerations ................................................................................................................ 8 Screened Alignments .............................................................................................................. 8 Tier 2 – Initial Hydromodeling of Structural Measures............................................................ 10 Full Barrier vs. Weir Options................................................................................................ 11 State’s Lake Borgne Alignment (‘S’) ................................................................................... 12 Open vs. Closed Tidal Passes ............................................................................................... 12 Tier 3 – Final Screening of Structural Alternatives .................................................................. 12 West Shore Alignment Variations ........................................................................................ 16 North Shore Alignment Refinements.................................................................................... 17 Other Findings ...................................................................................................................... 19 Structural Measures to be Included in Planning Unit 1 Alternatives........................................ 19 PLANNING UNIT 2..................................................................................................................................................21 Tier 1 – Initial Screening of Structural Alignments.................................................................. 21 Tier 2 – Initial Hydromodeling of Structural Measures............................................................ 25 Full Barrier vs. Weir Options................................................................................................ 26 Combining the Swamp and Highway 90 Alignments into the Ridge Alignment................. 26 Tier 3 – Final Screening of Structural Alternatives .................................................................. 27 Structural Measures to be Included in Planning Unit 2 Alternatives........................................ 30 SPECIAL CASE: LOWER PLAQUEMINES PARISH ........................................................................................31 Tier 1 – Initial Screening of Structural Alignments.................................................................. 32 Tier 2 – Initial Hydromodeling of Structural Measures............................................................ 33 PLANNING UNIT 3A ...............................................................................................................................................34 Tier 1 – Initial Screening of Structural Alignments.................................................................. 34 Tier 2 – Initial Hydromodeling of Structural Measures............................................................ 37 Tier 3 – Final Screening of Structural Alternatives .................................................................. 40 Structural Measures to be included in Planning Unit 3a Alternatives ...................................... 42 PLANNING UNIT 3B ...............................................................................................................................................43 Tier 1 – Initial Screening of Structural Alignments.................................................................. 43 Tier 2 – Initial Hydromodeling of Structural Measures............................................................ 45 Tier 3 – Final Screening of Structural Alternatives .................................................................. 47 Structural Measures to be included in Planning Unit 3b Alternatives...................................... 49 PLANNING UNIT 4..................................................................................................................................................50 Tier 1 – Initial Screening of Structural Alignments.................................................................. 50 i Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Tier 2 – Initial Hydromodeling of Structural Measures............................................................ 54 Tier 3 – Final Screening of Structural Alternatives .................................................................. 56 Structural Measures to be included in Planning Unit 4 Alternatives........................................ 58 SUMMARY................................................................................................................................................................59 List of Tables Table 1. Tier 3 Screening Attributes............................................................................................... 3 Table 2. Planning Unit 1 Codes from Plan Formulation Atlas used for Tier 1 Screening. ............ 6 Table 3. Rough Order of Magnitude Cost Estimates for Levee Alignments at Lake Pontchartrain and Lake Borgne in Planning Unit 1............................................................................................... 8 Table 4. Initial Screening of Planning Unit 1 Structural Measures ................................................ 9 Table 5. Planning Unit 1 Codes used for Tier 2 and Tier 3 Screening ......................................... 10 Table 6. Variation in Surge Elevation Impacts Mississippi Coast................................................ 11 Table 7. Design Elevations and Costs for Full Barrier vs. Weir Barrier ...................................... 11 Table 8. Planning Unit 1 Ranking of Measures............................................................................ 13 Table 9. Planning Unit 2 Codes from Plan Formulation Atlas used for Tier 1 Screening ........... 22 Table 10. Initial Screening of Planning Unit 2 Structural Measures ............................................ 24 Table 11. Planning Unit 2 Codes used for Tier 2 and Tier 3 Screening ...................................... 25 Table 12. Planning Unit 2 Ranking of Measures.......................................................................... 28 Table 13. Screening Results for Lower Plaquemines Parish ........................................................ 33 Table 14. Planning Unit 3a Codes from Plan Formulation Atlas used for Tier 1 Screening........ 34 Table 15. Initial Screening of Planning Unit 3a Structural Measures .......................................... 37 Figure 18. Reformulated Morganza Levee Alignment with Morgan City Ring Levee................ 38 Table 16. Planning Unit 3a Codes used for Tier 2 and Tier 3 Screening .................................... 39 Table 17. Planning Unit 3a Ranking of Measures ........................................................................ 41 Table 18. Planning Unit 3b Codes from Plan Formulation Atlas used for Tier 1 Screening ....... 43 Table 19. Initial Screening of Planning Unit 3b Structural Measures .......................................... 45 Table 20. Planning Unit 3b Codes used for Tier 2 and Tier 3 Screening ..................................... 46 Table 21. Planning Unit 3b Ranking of Measures........................................................................ 48 Table 22. Planning Unit 4 Codes from Plan Formulation Atlas used for Tier 1 Screening ......... 51 Table 23. Initial Screening of Planning Unit 4 Structural Measures ............................................ 53 Table 24. Planning Unit 4 Codes used for Tier 2 and Tier 3 Screening ...................................... 56 Table 25. Planning Unit 4 Ranking of Measures.......................................................................... 57 ii Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix List of Figures Figure 1. LACPR Planning Area and Planning Units..................................................................... 4 Figure 2. Example of a Lake Pontchartrain Surge Reduction Alignment from the Plan Formulation Atlas ........................................................................................................................... 6 Figure 4. Various Surge Reduction Alignments (1 through 5 and ‘S’) and Golden Triangle Alignments (‘a’ and ‘b’) ................................................................................................................. 7 Figure 5. West Shore Alignment Options..................................................................................... 17 Figure 6. Reformulated North Shore Alignment. ......................................................................... 18 Figure 8. GIWW Alignment from the Plan Formulation Atlas .................................................... 22 Figure 10. Swamp Alignment from the Plan Formulation Atlas .................................................. 23 Figure 15. Example Morganza to the Gulf Alignment from the Plan Formulation Atlas ............ 35 Figure 16. Atchafalaya Backwater Alignment from the Plan Formulation Atlas......................... 36 Figure 17. Reformulated Morganza Levee Alignment with Tie-in West of Morgan City ........... 38 Figure 19. Reformulated GIWW Alignment ................................................................................ 39 Figure 22. Reformulated Ring Levee Alignment ......................................................................... 46 Figure 23. Example Ring Levee Alignment from Plan Formulation Atlas .................................. 51 Figure 25. Highway 82 Alignment from Plan Formulation Atlas ................................................ 52 Figure 27. Reformulated GIWW Alignment (with tie in to Planning Unit 3b)............................ 54 Figure 28. Reformulated GIWW Alignment (stand alone for Planning Unit 4). ......................... 55 iii Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Purpose The Louisiana Coastal Protection and Restoration (LACPR) Technical Report has been developed by the United States Army Corps of Engineers (USACE) in response to Public Laws 109-103 and 109-148. Under these laws, Congress and the President directed the Secretary of the Army, acting through the Chief of Engineers, to: • • • • Conduct a comprehensive hurricane protection analysis and design in close coordination with the State of Louisiana and its appropriate agencies; Develop and present a full range of flood control, coastal restoration, and hurricane protection measures exclusive of normal policy considerations for South Louisiana; Consider providing protection for a storm surge equivalent to a Category 5 hurricane; and Submit preliminary and final technical reports. The purpose of this appendix is to support the formulation of structural hurricane risk reduction and flood control measures for LACPR, which is discussed in the main technical report. Introduction Structural, nonstructural, and coastal restoration measures are the building blocks of alternative plans for LACPR. An alternative plan is a set of one or more measures functioning together to address one or more planning objectives. Structural measures for LACPR primarily consist of physical structures that reduce surge and wave run-up, such as continuous or ring levees on land connected to floodgates acting as waterway barriers, where necessary. The first step in the formulation of measures involved extensive public involvement in partnership with the State of Louisiana. The USACE partnered with the State of Louisiana to identify and evaluate hurricane risk reduction strategies for South Louisiana. Through this partnership, the State developed a Master Plan to provide a long-term vision for hurricane risk reduction and coastal restoration. Numerous risk reduction measures were identified during the development of the State Master Plan. The LACPR Plan Formulation Atlas, which can be viewed and downloaded at http://www.lacpr.usace.army.mil/ documents the extensive collaborative identification of the coastal protection and restoration measures for South Louisiana. The next step in the plan formulation process was the screening and refinement of measures. This Structural Plan Component Appendix describes how structural measures were screened and refined to a smaller and more manageable set of options for integration with the nonstructural and coastal restoration components of the LACPR alternatives. Project guidance for LACPR required that LACPR investigate measures that address hurricane storm risk reduction for a 100-year event, a Katrina like event (or low Category 5 event), and a high Category 5 event for coastal Louisiana. For LACPR, the Category 5 hurricane event is represented by a range of frequencies, i.e. the 400-year event represents a "low" Category 5 hurricane and the 1000-yr event represents a "high" Category 5 event. In addition, the alternatives developed vary in the geographical area receiving such risk reduction, ranging from 1 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix only providing risk reduction to specific areas of significant concentration of assets or population, as provided for by local or regional ring levees, to providing risk reduction for the entire coastal area, as considered in the nonstructural only and comprehensive alternatives. All the 400-yr and 1000-yr alternatives do provide some level of Category 5 risk reduction, to at least some, if not all of the coastal area, as stated. Also many of the 100-year measures or alternatives (e.g., the barrier-weirs) provide for varying levels of Category 5 risk reduction to some specific areas by increasing the design levels of existing or proposed levee systems by providing for an outer barrier line of defense. The consideration and screening of nonstructural and coastal management features are described in the Nonstructural Plan Component Appendix and Coastal Restoration Plan Component and Environmental Metrics Appendix, respectively. The coastal appendix also contains discussions of direct and indirect environmental impacts and mitigation requirements that would result from construction of structural plans. The final step in the plan formulation process, combining measures into alternative plans, entailed the consideration of reasonable and efficient integration of structural measures with nonstructural and coastal restoration measures into viable alternative plans. The Technical Report presents the performance of various alternative plans and illustrates tradeoffs between and among plans on specific objectives and overall program goals. Stakeholder input was incorporated into the plan comparison step using a Multi-Criteria Decision Analysis (MCDA) tool as described in the Risk-informed Decision Framework Appendix. Alternative plans are not limited to those the U.S. Army Corps of Engineers (USACE) could implement directly under current authorities. Structural measures that could be implemented under the authorities of other Federal agencies, State and local entities, and non-government interests have also been considered. For more information on the LACPR Congressional authority, plan formulation strategy and planning objectives, refer to the main report. Three-Tiered Screening Process A three-tiered screening process was used to reduce possible structural measures, alignments and alternatives to a more manageable number for further evaluation and consideration across a wide range of stakeholder interests. • • • Tier 1 – Initial Screening of Structural Alignments. Alignments from the Plan Formulation Atlas were screened considering preliminary construction costs, constructability, and environmental impacts. Tier 2 – Initial Hydromodeling of Structural Measures. Initial hydromodeling results were used to further screen the number of alignments and strategies. Tier 3 – Final Screening of Structural Alternatives. The final step set each remaining alignment at three design heights, 100-year, 400-year, and 1000-year, to create a set of structural alternatives, which were then screened using six attributes (see Table 1). 2 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Table 1. Tier 3 Screening Attributes ATTRIBUTE DESCRIPTION Cost Effectiveness Ratio of present value costs/average annual risk reduction Present Value Costs Present value at 2025 for life-cycle costs Annual Equivalent Flood Damages With-project residual damages Population Impacted Number of people who would be inundated in the year 2075 for a 400-year frequency event Construction Period Years required to complete initial construction Direct Impact – Wetlands Wetland acreage impacted by proposed levees For the third tier screening, each structural measure was rated based on these six attributes. In order to have comparable scores for each of these attributes, each had to be normalized or converted to a range of 0-1 where the lower value is preferred. All screening attribute values presented in this appendix are based on earlier iterations of data development (or preliminary data) using primarily 2010 base conditions for estimating withproject damages. As such, values shown do not represent the metric and evaluation data presented in the Evaluation Results Appendix. Details on the hydromodeling results used to screen measures in Tier 2 are contained in Volume 2 (Annex A) of the Hydraulics and Hydrology Appendix. Organization of This Appendix This appendix is organized by planning unit as shown in Figure 1. 3 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Figure 1. LACPR Planning Area and Planning Units Each of the planning unit sections generally follows the same format: • Brief description of the planning unit. • Tier 1 screening – initial screening of structural alignments. o Codes used to refer to measures screened from the Plan Formulation Atlas. o Maps and text describing structural measure variations from the Plan Formulation Atlas. o Table(s) and text describing which measures passed/failed the Tier 1 screening and why. • Tier 2 screening – initial hydromodeling of structural measures. o List of remaining formulation issues from Tier 1 screening. o Codes used to refer to measures in the Tier 2 and Tier 3 screening. o Maps showing reformulated structural alignments. o Tables and text describing how hydromodeling results were used to screen and/or reformulate measures. • Tier 3 screening – final screening of structural alternatives using six attributes. o List of remaining formulation issues from Tier 2 screening. o Table showing ranking of measures followed by descriptions of why each measure was chosen for the overall LACPR alternatives. Descriptions of each of the measures to be evaluated with the overall LACPR alternatives. 4 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Planning Unit 1 The following sections provide details on the tiered screening of measures and alignments for Planning Unit 1. Planning Unit 1 is bordered between the (1) Mississippi River to the west, (2) Gulf of Mexico to the south and east, (3) Pearl River on the east, and (4) potential extent of surge inundation to the north. The western border of this planning unit is protected against hurricane surges translating up the Mississippi River by the Mississippi River levees. Planning Unit 1 is the most densely populated planning unit in coastal Louisiana, containing approximately one million residents, or 47 percent, of the entire planning area’s population. The major portion of greater New Orleans is located within the planning unit. The population at risk lives between the Mississippi River east bank levee system and the shoreline areas of Lake Pontchartrain and Lake Borgne. Structural measures attenuate surge from two main water bodies. The first water body is Lake Borgne to the east of New Orleans. Lake Borgne is connected to the Gulf Intracoastal Waterway (GIWW) and its branch channels which includes the de-authorized portion of the Mississippi River Gulf Outlet (MRGO) and the Industrial Canal. This navigation system bisects East New Orleans. Structural measures would need to address levee improvements and/or navigation gates. The second water body is Lake Pontchartrain which has two channels connecting it to Lake Borgne – Chef Menteur and The Rigoletes. Structural measures would need to address levee improvements and/or lake closures. The tradeoff for providing structural risk reduction to populated areas along the Lake Pontchartrain perimeter range from closing or limiting flow through the two passes – at least during surge conditions - to creating and/or raising levees and floodwalls between the lake and populated areas. The lower portion of Plaquemines Parish is the area south of metropolitan New Orleans located along the “bird’s foot” stretch of land terminating at the mouth of the Mississippi River. Lower Plaquemines Parish has limited opportunity for structural considerations other than ring levees to protect isolated communities and spillways in the Mississippi River levee system to lower the surge elevations. Levee height considerations are impacted by soil foundation strength and land availability for conventional levee width requirements. Screening of structural measures for this area is discussed following the details on Planning Unit 1 and Planning Unit 2. Tier 1 – Initial Screening of Structural Alignments The Plan Formulation Atlas identified two primary strategies for structural risk reduction in Planning Unit 1. They include a Lake Pontchartrain surge reduction alignment (Figure 2) at the mouth of Lake Pontchartrain and a high level alignment (Figure 3). The Lake Pontchartrain surge reduction alignment proposes to add a levee across the mouth of Lake Pontchartrain with storm gates closing the passes at Chef Menteur and The Rigoletes during a storm event. Figure 4 displays six different surge reduction alignments (shown as 1 through 5 and the letter ‘S’) and two different alignments within the area known as the Golden Triangle (shown as a and b). The high level alignment proposes to raise levees on the South Shore of Lake Pontchartrain to a higher level of risk reduction and to add levees on the North Shore of Lake Pontchartrain. Within the two primary strategies, the Plan Formulation Atlas identified 17 variations. Table 2 describes 5 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix the codes used in the Plan Formulation Atlas and for Tier 1 screening for measures in Planning Unit 1. Table 2. Planning Unit 1 Codes from Plan Formulation Atlas used for Tier 1 Screening. Code PU1-LP-HL-State -# a b Measure Code Description, e.g. PU1-LP-1a Planning Unit 1 Lake Pontchartrain surge reduction alignment High level alignment Alignment that was part of the preliminary draft State Master Plan Variations to the primary alignments, if applicable (see Figure 4) Golden Triangle alignment at the confluence of the GIWW and MRGO Alignment at the edge of the Golden Triangle and Lake Borgne Figure 2. Example of a Lake Pontchartrain Surge Reduction Alignment from the Plan Formulation Atlas 6 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Figure 3. Example of a High Level Alignment from the Plan Formulation Atlas Figure 4. Various Surge Reduction Alignments (1 through 5 and ‘S’) and Golden Triangle Alignments (‘a’ and ‘b’) 7 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Cost Considerations Rough order of magnitude costs were developed for each of the Surge Reduction Alignments and the Golden Triangle alignments. Alignment ‘a’ refers to the levee alignment that would cross the Golden Triangle wetlands at the confluence of the Gulf Intracoastal Waterway and the Mississippi River Gulf Outlet. Alignment ‘a’ is part of the baseline conditions scheduled to be in place around 2011. Alignment ‘b’ follows along the edge of the Golden Triangle and Lake Borgne and would provide a secondary line of defense to Alignment ‘a.’ Table 3 shows the initial construction and real estate costs for the levee alignments at Lake Ponchartrain and Lake Borgne. Table 3. Rough Order of Magnitude Cost Estimates for Levee Alignments at Lake Pontchartrain and Lake Borgne in Planning Unit 1 A - Alignment Alignment LP-1a LP-2a LP-3a LP-4a1 LP-5a1 Initial Costs ($billions) $10.8B $10.8B $20B $26.5B $26.3B B - Alignment Initial Costs ($billions) $10.1B $10B $19.2B $25.7B $25.5B Alignment LP-1b LP-2b LP-3b LP-4b1 LP-5b1 Note: Planning Unit 1 cost estimates assume the levees are 30 feet high and are built from the ground up. The cost estimates for the ‘a’ alignments would go down if the new 100-year levees being in place are taken into account. Costs assume geotextile levee construction (i.e. traditional construction methods). Screened Alignments Table 4 lists the variations of both the Lake Pontchartrain surge reduction alignments and the High Level alignments and describes why some alignment variations were eliminated from further consideration at this time. As indicated in Table 4 alignments 3, 4 and 5 were eliminated from further screening due to the extremely high cost as compared to alignments 1 and 2 which provide similar output. 8 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Table 4. Initial Screening of Planning Unit 1 Structural Measures PU1-LP-1a and 1b Pass/ Fail Pass PU1-LP-2a and 2b Pass PU1-LP-3a and 3b Fail PU1-LP-4a1, 4b1, 4a2, and 4b2 Fail PU1-LP-5a1, 5b1, 5a2, and 5b2 Fail PU1-LP-State Pass PU1-HL-1a and 1b Pass Measure Code(s) Comments These alignments follow Highway 90 along the landbridge. The State screened this measure out because of public opposition (multiple landowners), so it is not included in the State Master Plan; however, the LACPR team felt that the multiple landowner issue is not insurmountable and carried this alignment forward into the next screening because of its good soil foundation. Costs for 1a and 1b are same magnitude as for 2a and 2b below (~$10 – 11 billion). These alignments follow the GIWW/railroad and are essentially the same as those represented in the State Master Plan. Costs for 2a and 2b are same magnitude as for 1a and 1b above ($10 – 11 billion). These alignments cross Lake St. Catherine and have significant constructability, operability, and environmental concerns. In comparison to alignments 1 and 2 above, alignment 3 has more constructability, operability, and environmental concerns. In addition, the cost is higher (~$19 – 20 billion). Constructability, operability, and cost concerns. Costs for these measures are approximately 2.5 times the costs of LP-1 and LP-2 (~$25 – 27 billion). In comparison to alignments 1 and 2 above, these alignments have more constructability and operability concerns. In addition, the costs are higher (~$25 – 27 billion) Constructability, operability, and cost concerns. Costs for these measures are approximately 2.5 times the costs of LP-1 and LP-2 (~$25 – 27 billion). In comparison to alignments 1 and 2 above, these alignments have more constructability and operability concerns. In addition, the costs are higher (~$25 – 27 billion) The State Master Plan presented three barrier alignments. Two of the alignments approximately correspond to PU1LP-2a and PU1-LP-2b. Specific hydromodeling data will be available for the third State weir alignment (‘S’) across Lake Borgne. Presents an alternative to the Surge Reduction Plan concept and will be carried through into the MCDA process. Note: Planning Unit 1 preliminary cost estimates assumed the levees are 30 feet high and are built from the ground up. The cost estimates for the ‘a’ alignments would go down if the new 100-year levees being in place are taken into account. Costs assume geotextile levee construction (i.e. traditional construction methods). 9 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Tier 2 – Initial Hydromodeling of Structural Measures In addition to the initial screening evaluation, additional hydromodeling was necessary to resolve and further refine the possible structural measures in Planning Unit 1. Remaining formulation issues included: • • • • • • • High level versus Lake Pontchartrain surge reduction alignments. Full barrier (non-overtopping) versus weir (overtopping) designs for the Lake Pontchartrain surge reduction alignments. Open versus closed tidal pass designs for the Lake Pontchartrain surge reduction alignments. Lake Borgne alignment (‘S’). Golden Triangle alignments (‘a’ or ‘b’). Inclusion or exclusion of North Shore, West Shore, and Oakville extension. Design level of risk reduction. For this tier, barrier versus weir and open versus closed tidal gates were evaluated. During this step, a range of alignments were formulated to address the remaining formulation issues. With the inclusion of different levels of risk reduction, the naming convention for the structural measures was revised slightly from previous screening nomenclature. Table 5 describes an example of the coding. Table 5. Planning Unit 1 Codes used for Tier 2 and Tier 3 Screening Code PU1-LP-HL-a-b-100-400-1000-1 -2 -3 Measure Code Description, e.g. PU1-LP-a-100-1 Planning Unit 1 Lake Pontchartrain surge reduction alignment High level alignment Golden Triangle alignment at the confluence of the GIWW and MRGO Alignment at the edge of the Golden Triangle and Lake Borgne 100-year design level 400-year design level 1000-year design level All PU1 primary alternatives include the Lake Pontchartrain and Vicinity Project levees and upper Plaquemines levees. The primary alignments for ‘LP’ also include a barrier-weir across the mouth of Lake Pontchartrain with a tieback to high ground east of Slidell. Primary alignment plus North Shore and West Shore levees. Primary alignment plus Slidell and West Shore levees. 10 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Full Barrier vs. Weir Options The full barrier (non-overtopping) designs were compared to the weir barrier (overtopping) designs for the Lake Pontchartrain surge reduction alignments to determine the preferred design configuration. Based on the preliminary surge level results (see Table 6), the non-overtopping design increased surges along parts of the Mississippi coastline by up to 5.4 feet while the weir design increased surge by 3.2 feet for hurricanes of intensity greater than a 400-year event. Table 6. Variation in Surge Elevation Impacts Mississippi Coast Distance from LA State Border 0 miles 18 miles 26 miles 49 miles 70 miles Average/Maximum Difference from Baseline Surge Elevations Area Weir (feet) Barrier (feet) Pearl River (Hwy 90) +2.3 / +3.2 + 3.6 / +5.4 Clermont Harbor +0.7 / +0.9 +1.1 / +2.0 Bay Saint Louis +0.6 / +0.9 +1.0 / +1.9 Gulfport +0.2 / +0.5 +0.4 / +1.2 Biloxi +0.2 / +0.4 +0.3 / +1.0 As shown in the above table, measures in Planning Unit 1 have the potential to impact the Mississippi coast. Such impacts have been further addressed in a systems analysis conducted in coordination with the Mississippi Coastal Improvements Program (MsCIP) team. A summary of the potential regional impacts are addressed in the Systems Analysis section of the main report. The design height of a non-overtopping levee along the Lake Pontchartrain surge reduction (‘LP-’) alignments would exceed 24 feet for the 100-year storm event (see Table 7), which means high costs and constructability issues. Table 7. Design Elevations and Costs for Full Barrier vs. Weir Barrier Full Barrier Alignment LP-b-100-1 LP-b-400-1 LP-b-1000-1 LP-b-100-2 LP-b-400-2 LP-b-1000-2 Weir Barrier Geo Textile Soil Mix Overflow Elev. (ft) Elev. (ft) ($billions) ($billions) ($billions) $7B $9.5B 25 $4.5B 12.5 $18.5B $19.9B 32 $12.8B 12.5 $22.4B $24.9B 36 $16.1B 12.5 $12.6B $20.6B 25 $10.6B 12.5 $27.1B $33.5B 32 $22.4B 12.5 $32.2B $40B 36 $27.3B 12.5 In summary, the non-overtopping barrier has been eliminated from further consideration because of cost constraints, engineering feasibility issues, and potential impacts to Mississippi. 11 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix State’s Lake Borgne Alignment (‘S’) The State’s Lake Borgne alignment was screened out for the same reason that the full barrier options were screened out. Hydromodeling results show unacceptable increases in water levels to the State of Mississippi. Also, this alignment presents many costly constructability issues and challenges. Open vs. Closed Tidal Passes A second design consideration for the Lake Pontchartrain surge reduction measure was whether to close the tidal passes at The Rigoletes and Chef Menteur passes with floodgates or whether to leave the passes open for environmental reasons. Evaluation of the hydromodel output for the open tidal passes revealed limited reduction in surge levels within Lake Pontchartrain. Therefore, it was determined that the closed tidal passes provide the best engineering solution for all storm conditions if a barrier plan is selected. Tier 3 – Final Screening of Structural Alternatives Based on the Tier 2 screening, the preliminary measures or variations of measures for further consideration included: • • • • High level versus surge reduction plans. Golden Triangle alignment ‘a’ versus alignment ‘b.’ North Shore levee or Slidell ring levee. West Shore (Laplace). As part of the Tier 3 screening, structural measures were subjected to analysis using 100, 400, and 1000-year design heights for each levee alignment considered. This resulted in the development of 16 variations of the High Level Plan and 18 variations of the Lake Pontchartrain Surge Reduction. These structural measures were then ranked using the multiple attributes previously described in Table 1. Table 8 displays the ranking of the 34 measures and the screening attribute values used to conduct the ranking. 12 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Table 8. Planning Unit 1 Ranking of Measures Measures LP-a-100-1 LP-b-100-1 HL-a-100-3 HL-a-100-2 LP-b-400-1 LP-a-100-3 LP-a-400-1 HL-b-100-3 LP-a-100-2 LP-b-100-3 HL-b-100-2 LP-b-100-2 LP-b-1000-1 HL-a-400-1 LP-a-1000-1 HL-b-400-3 HL-b-400-1 LP-b-400-3 LP-a-400-3 HL-a-400-3 LP-b-400-2 HL-b-400-2 LP-a-400-2 HL-a-400-2 HL-a-1000-1 HL-b-1000-1 LP-b-1000-3 HL-b-1000-3 LP-a-1000-3 LP-b-1000-2 Cost Effectiveness Annual Equiv. Flood Damages Screening Attributes 2075 Pop. Present Value Impacted 400-yr Costs Event Construction Period Ratio* Value** $ Million Value** People Value** $ Million Value** Years Value** 29.49 42.86 47.78 49.44 67.24 55.77 72.96 59.79 57.33 63.92 59.84 64.79 87.47 106.37 93.58 92.13 119.45 83.40 87.68 96.85 83.64 91.44 87.20 95.76 131.12 147.97 100.76 111.76 105.28 100.88 0.20 0.29 0.32 0.35 0.45 0.38 0.49 0.40 0.39 0.43 0.42 0.44 0.59 0.72 0.63 0.62 0.81 0.56 0.59 0.65 0.57 0.62 0.59 0.65 0.89 1.00 0.68 0.76 0.71 0.68 793 781 754 714 623 684 624 751 655 672 711 643 614 734 615 522 783 488 489 523 455 477 456 478 722 772 471 501 472 441 1.00 0.98 0.95 0.90 0.79 0.86 0.79 0.95 0.83 0.85 0.90 0.81 0.77 0.93 0.78 0.66 0.99 0.62 0.62 0.66 0.57 0.60 0.58 0.60 0.91 0.97 0.59 0.63 0.60 0.56 657,708 634,659 706,211 691,138 429,604 649,395 429,915 705,491 638,120 626,346 690,418 615,071 415,159 466,706 415,266 376,731 466,309 350,257 350,568 377,128 324,873 343,385 325,184 343,782 436,473 436,275 330,322 337,952 330,429 307,571 0.93 0.90 1.00 0.98 0.61 0.92 0.61 1.00 0.90 0.89 0.98 0.87 0.59 0.66 0.59 0.53 0.66 0.50 0.50 0.53 0.46 0.49 0.46 0.49 0.62 0.62 0.47 0.48 0.47 0.44 6,459 9,900 12,327 14,732 26,157 18,291 28,310 15,605 20,468 21,732 18,012 23,908 34,813 29,570 37,153 45,143 27,354 43,701 45,856 47,359 46,587 48,920 48,484 51,136 38,025 35,512 54,510 57,111 56,850 57,603 0.10 0.15 0.19 0.23 0.41 0.29 0.44 0.24 0.32 0.34 0.28 0.37 0.54 0.46 0.58 0.70 0.43 0.68 0.72 0.74 0.73 0.76 0.76 0.80 0.59 0.55 0.85 0.89 0.89 0.90 14 14 12 12 16 14 16 12 14 14 12 14 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 0.88 0.88 0.75 0.75 1.00 0.88 1.00 0.75 0.88 0.88 0.75 0.88 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 13 Direct ImpactWetlands Acres 980 1,554 3,642 4,686 4,238 3,668 4,055 4,220 4,541 4,242 5,265 5,115 5,100 2,540 4,924 5,661 2,209 7,587 7,404 5,993 8,590 7,498 8,406 7,830 3,211 2,940 9,042 7,491 8,865 10,081 Total Value Score*** Rank 3.21 3.36 3.59 3.69 3.69 3.69 3.74 3.77 3.78 3.81 3.87 3.89 4.02 4.03 4.08 4.10 4.11 4.13 4.18 4.20 4.20 4.24 4.24 4.33 4.34 4.45 4.52 4.52 4.57 4.60 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Value** 0.10 0.16 0.37 0.48 0.43 0.37 0.41 0.43 0.46 0.43 0.54 0.52 0.52 0.26 0.50 0.58 0.23 0.78 0.76 0.61 0.88 0.77 0.86 0.80 0.33 0.30 0.92 0.77 0.91 1.03 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Measures HL-a-1000-3 LP-a-1000-2 HL-b-1000-2 HL-a-1000-2 Cost Effectiveness Annual Equiv. Flood Damages Screening Attributes 2075 Pop. Present Value Impacted 400-yr Costs Event Construction Period Ratio* Value** $ Million Value** People Value** $ Million Value** Years Value** 116.91 105.16 112.17 116.75 0.79 0.71 0.76 0.79 502 442 463 463 0.63 0.56 0.58 0.58 338,150 307,678 310,658 310,856 0.48 0.44 0.44 0.44 59,625 59,943 61,583 64,096 0.93 0.94 0.96 1.00 16 16 16 16 1.00 1.00 1.00 1.00 Direct ImpactWetlands Acres 7,763 9,905 9,516 9,787 14 Rank 4.63 4.65 4.71 4.81 31 32 33 34 Value** 0.79 1.01 0.97 1.00 Indicates structural measure is included in the overall set of LACPR alternatives to be evaluated in detail. * Cost Effectiveness Ratio = Total Present Value Costs /Average Annual Equivalent Risk Reduction ** Value is the normalized value for the attribute where a value of 1.00 represents the greatest is the largest (lower is better) ***Total of Normalized Values (lower is better) Total Value Score*** Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Based on the ranking above and in consideration of the need to investigate a range of different ways to reduce the risk of hurricane storm damages the following structural measures were selected to be carried forward into the set of alternatives to be evaluated in the overall LACPR effort (listed in order of rankings): LP-a-100-1: Of all variations considered, this is the least expensive and has the lowest cost per average annual risk reduction (or biggest bang for the buck) and has the least direct impact on wetlands than any other plan; however, the spatial extent of risk reduction is limited to metropolitan New Orleans and vicinity. It should be noted that although the LP-b-100-1 structural measure was ranked 2nd among all structural measures in Planning Unit 1, it costs considerably more than LP-a-100-1 and has greater wetland impacts. Therefore, LP-b-100-1 was eliminated from further consideration. HL-a-100-3: This measure ranked 3rd among the structural measures in Planning Unit 1 and is the least costly High Level Plan. HL-a-100-2: This measure ranked 4th among the structural measures in Planning Unit 1. This measure costs significantly less than the equivalent Surge Reduction measure (LP-a-100-2) and was selected because of its ranking. LP-b-400-1: This measure ranked 5th. In regards to risk reduction benefits, LP-b-400-1 performs similarly to LP-a-400-1 (ranked 7th) but costs less. LP-a-100-3: This measure ranked 6th among the structural measures in Planning Unit 1. It was selected to be included in the set of alternatives because it provides risk reduction to other areas besides metropolitan New Orleans (i.e., Laplace, Slidell, Oakville extension) and has similar overall score (3.69) with the previous 2 structural measures. LP-a-100-2: This measure ranked 9th among the structural measures in Planning Unit 1. This measure was selected because it provides structural risk reduction for a 100-year frequency event to developed areas on the North Shore as well as Laplace, Slidell and Oakville extension. However, it is considerably more expensive than its equivalent High Level measure (HL-a-1002) and will take longer to construct. LP-b-1000-1: This measure ranked 13th among the structural measures in Planning Unit 1. This measure provides the least costly way to provide Category 5 level of risk reduction within Planning Unit 1. HL-b-400-3: This measure ranked 16th among the structural measures in Planning Unit 1. While more expensive than its equivalent Surge Reduction plan (LP-b-400-3), it impacts considerably less wetlands. This measure provides 400-year level of protection to other areas besides metro New Orleans (i.e., Laplace, Slidell, Oakville extension). LP-b-400-3: This measure ranked 18th among the structural measures in Planning Unit 1. This measure was selected for comparison with its equivalent Surge Reduction plan (HL-b-400-3). 15 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix HL-b-400-2: This measure ranked 22nd among the structural measures in Planning Unit 1. This measure was selected because it provides structural risk reduction for a 400-year frequency event to developed areas on the North Shore. This measure allows for incremental comparison to HLb-400-3, which provides risk reduction to only the Slidell areas on the North Shore. Selection of this measure allows for consideration of a wider array of options for the North Shore using High Level measures. LP-b-1000-2: This measure ranked 30th among the structural measures in Planning Unit 1. This measure provides the greatest average annual risk reduction benefits and Category 5 risk reduction to all areas (except Plaquemines). While these ten structural measures do not represent all measures in terms of reducing average annual damages, this array encompasses a sufficient range of structural risk reduction measures from which a preferred comprehensive plan or strategy can be identified. Absent from this array of options are measures that tradeoff risk reduction of site-specific areas within Planning Unit 1. These areas can be investigated incrementally allowing for comparison of structural vs. nonstructural measures. Specifically, risk reduction of the North Shore of Lake Pontchartrain will be evaluated incrementally to address costs, risk reduction, significant engineering problems/challenges (major water courses, large pumping requirements, and lack of acceptability from locals). In addition, other areas such as Laplace and Slidell will be evaluated independently and with various levels (100, 400 and 1000-year) of risk reduction. The following sections briefly describe the North and West Shore areas. West Shore Alignment Variations Figure 5 presents the West Shore or Laplace alignment variations being investigated through the West Shore Lake Pontchartrain Feasibility Study. For the level of analysis in the LACPR effort, the “LACPR Alignment” acts as a representative alignment of Alignments A through C. Selection of the exact alignment would take place through the West Shore Lake Pontchartrain Feasibility Study. 16 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Figure 5. West Shore Alignment Options. North Shore Alignment Refinements Once inundation data became available, the team was able to refine the North Shore alignment from a continuous levee as shown previously in Figure 2 to a series of ring levees as shown in Figure 6. These ring levees are expected to be more technically and economically viable and more publicly acceptable than a long continuous levee and will therefore be carried forward into the reevaluation in place of the continuous levee. In addition, the Slidell ring levee previously shown in Figure 3 was modified slightly as shown in Figure 7. 17 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Figure 6. Reformulated North Shore Alignment. Figure 7. Reformulated Slidell Ring Levee. 18 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Other Findings Other findings from this analysis included the following: 1) The Golden Triangle alignment ‘b’ was generally more cost effective for the 400 and 1000-year level of risk reduction than alignment ‘a.’ 2) Providing 1000-year level of risk reduction through structural measures may appear to be a poor financial decision if considering average annual values. For the 1000-year plans, there is a 30 percent increase in cost and less than one percent increase in average annual damages prevented compared to the equivalent 400-year plans. This alone should not be reason to dismiss higher levels of risk reduction. Therefore, a structural measure that provides 1000-year level of risk reduction is kept for consideration during the MCDA process during which additional metrics can and will be considered. Structural Measures to be Included in Planning Unit 1 Alternatives Below is the array of options to be included as structural components of alternatives to be considered for detailed analysis for Planning Unit 1. These structural measures allow for comparison of further improvements to the Lake Pontchartrain and Vicinity project as well as the North Shore of Metro New Orleans (at similar levels and areas of risk reduction) for 100-year, 400-year and 1000-year levels of risk reduction. For the Planning Unit 1 alternatives, these structural components are combined with coastal restoration and nonstructural measures to provide comprehensive risk reduction. Lake Pontchartrain Barrier Levee Alignments: LP-a-100-1: This structural option targets a 100-year level of risk reduction. This structural option includes building a 12.5-foot elevation weir across the mouth of Lake Pontchartrain to act as a surge barrier and extending the levee system east of Slidell up to high ground near Interstate 59. Storm gates would close the passes at Chef Menteur and The Rigoletes. LP-a-100-2: This structural option targets a 100-year level of risk reduction. This structural option contains the same surge barrier weir as LP-1a-100-1 but it adds levee on the North Shore, a levee around Laplace, and a levee in Plaquemines Parish on the east bank of the Mississippi River across from Oakville. LP-a-100-3: This structural option targets a 100-year level of risk reduction. This structural option contains the same surge barrier weir as LP-1a-100-1 but it adds a ring levee around Slidell on the North Shore, a levee around Laplace, and a levee in Plaquemines Parish on the east bank of the Mississippi River across from Oakville. LP-b-400-1: This structural option targets a 400-year level of risk reduction. This structural option contains the same surge barrier weir as LP-1a-100-1 but it includes raising existing levees to a 400-year level of risk reduction. This option also includes a new levee approximately between Chef Menteur Pass and Bayou Dupre that would follow Lake Borgne along the edge of the wetlands; construction would include sector gates on both the MRGO and GIWW. 19 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix LP-b-400-3: This structural option targets a 400-year level of risk reduction. This structural option contains the same surge barrier weir as LP-1a-100-1 but it adds a ring levee around Slidell on the North Shore, a levee around Laplace, and a levee in Plaquemines Parish on the east bank of the Mississippi River across from Oakville. This option also includes a new levee approximately between Chef Menteur Pass and Bayou Dupre that would follow Lake Borgne along the edge of the wetlands; construction would include sector gates on both the MRGO and GIWW. LP-b-1000-1: This structural option targets a 1000-year level of risk reduction. This structural option contains the same surge barrier weir as LP-1a-100-1 but it includes raising existing levees to a 1000-year level of risk reduction. This option also includes a new levee approximately between Chef Menteur Pass and Bayou Dupre that would follow Lake Borgne along the edge of the wetlands; construction would include sector gates on both the MRGO and GIWW. LP-b-1000-2: This structural option targets a 1000-year level of risk reduction. This structural option contains the same surge barrier weir as LP-1a-100-1 but it adds a levee across the North Shore, a levee around Laplace, and a levee in Plaquemines Parish on the east bank of the Mississippi River across from Oakville. This option also includes a new levee approximately between Chef Menteur Pass and Bayou Dupre that would follow Lake Borgne along the edge of the wetlands; construction would include sector gates on both the MRGO and GIWW. Of all the structural measures, this measure contains the most structural components to provide a comprehensive 1000-year level of risk reduction to both the North and South Shore. High Level Levee Alignments: HL-a-100-2: This structural option targets a 100-year level of risk reduction. This structural option involves building new levees but without a surge reduction barrier across Lake Pontchartrain. The new levees would include a levee on the North Shore, a levee around Laplace, and a levee in Plaquemines Parish on the east bank of the Mississippi River across from Oakville. HL-a-100-3: This structural option targets a 100-year level of risk reduction. This structural option involves building new levees but without a surge reduction barrier across Lake Pontchartrain. The new levees would include a ring levee around Slidell on the North Shore, a levee around Laplace, and a levee in Plaquemines Parish on the east bank of the Mississippi River across from Oakville. HL-b-400-2: This structural option targets a 400-year level of risk reduction. This structural option involves building new levees but without a surge reduction barrier across Lake Pontchartrain. The new levees would include a levee on the North Shore, a levee around Laplace, and a levee in Plaquemines Parish on the east bank of the Mississippi River from Oakville. This option also includes a new levee approximately between Chef Menteur Pass and Bayou Dupre that would follow Lake Borgne along the edge of the wetlands; construction would include sector gates on both the MRGO and GIWW. 20 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix HL-b-400-3: This structural option targets a 400-year level of risk reduction. This structural option involves raising existing levees and building new levees but without a surge reduction barrier across Lake Pontchartrain. The new levees would include a ring levee around Slidell on the North Shore, a levee around Laplace, and a levee in Plaquemines Parish on the east bank of the Mississippi River across from Oakville. This option also includes a new levee approximately between Chef Menteur Pass and Bayou Dupre that would follow Lake Borgne along the edge of the wetlands; construction would include sector gates on both the MRGO and GIWW. Planning Unit 2 The following sections provide details on the tiered screening of measures and alignments for Planning Unit 2, a triangular shaped area beginning at Donaldsonville, then extending southeast along the Mississippi River to the Gulf of Mexico. This area then continues southwest of Grand Isle and Port Fourchon and northwest along Bayou Lafourche. Approximately 300,000 residents, or 14 percent, of the planning area population inhabits Planning Unit 2, containing the portion of the New Orleans metropolitan area located on the West Bank of the Mississippi River. Additionally, this planning unit contains Venice, Grand Isle, and portions of towns located along Bayou Lafourche such as Port Fourchon, Larose, Thibodaux, and Donaldsonville. The major Mississippi River ports, noted in the description of Planning Unit 1 also have infrastructure on the West Bank of the Mississippi River in Planning Unit 2. Additionally, this highly productive estuary is home to a population where the social and economic cultures have evolved around and are dependent upon the estuary’s natural resources. As discussed for Planning Unit 1, the lower portion of Plaquemines Parish is a special case; therefore, screening of structural measures for this area is discussed following the screening details of Planning Unit 2. Tier 1 – Initial Screening of Structural Alignments The Plan Formulation Atlas identified four primary strategies for structural risk reduction within Planning Unit 2. The alignment of the levees included the GIWW (three variations were considered including structural risk reduction for Lafitte and variations of where the levee ties into to the Mississippi River Levee System), Highway 90 alignment, Swamp alignment (later modified/combined with Highway 90 alignment and renamed to Ridge alignment) and two alignments along the West Bank Interior (improvement to existing West Bank levee and extension of the existing West Bank levee). Table 9 describes the codes used in the Plan Formulation Atlas and for Tier 1 screening for measures in Planning Unit 2. Figures 8 through 11 show examples of the various alignments. 21 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Table 9. Planning Unit 2 Codes from Plan Formulation Atlas used for Tier 1 Screening Code PU2-WBI-G-H -S -State -# Measure Code Description (e.g. PU2-G-1) Planning Unit 2 West Bank interior alignments GIWW levee alignment variation Highway 90 levee alignment Swamp alignment Alignment that was part of the preliminary draft State Master Plan Variations to the primary alignments (if applicable) Figure 8. GIWW Alignment from the Plan Formulation Atlas 22 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Figure 9. Highway 90 Alignment from the Plan Formulation Atlas Figure 10. Swamp Alignment from the Plan Formulation Atlas 23 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Figure 11. West Bank Interior Alignment from the Plan Formulation Atlas Through initial screening, in which preliminary construction costs as well as direct and indirect environmental impacts were considered, the number of variations was screened to five. Table 10 lists the variations of each of the alignments in Planning Unit 2 and describes why some alignment variations were eliminated from further consideration at this time. Table 10. Initial Screening of Planning Unit 2 Structural Measures Measure Code(s) PU2-G-1 Pass/Fail Comments Pass Essentially the same as the State’s GIWW alignment; however, the State plan includes a ring levee around Lafitte. Cost estimates range from ~$5B - $9B depending on the height and levee construction method (i.e., 30 feet geotextile, 30 feet soil mix, or 35 feet soil mix). Environmental concerns. Environmental concerns. Essentially the same as the State’s Highway 90 alignment. For a 25-foot levee, costs range from ~$10 – 15B depending on levee construction method (geotextile versus soil mix). Equivalent to the State’s swamp alignment. For a 20-foot levee, costs range from ~$13 – 30B depending on the levee construction method (geotextile versus soil mix). If the swamp alignment only needs to be 20 feet up to Vacherie and Thibodaux, costs could range from $11-22B. PU2-G-2 PU2-G-3 PU2-H Fail Fail Pass PU2-S Pass 24 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Measure Code(s) PU2-WBI-1 Pass/Fail Comments Pass A component of the swamp alignment and also the West Bank component of the high level plan considerations in PU1. A component of the swamp alignment and also the West Bank component of the high level plan considerations in PU1. This alignment was presented in the Preliminary Draft State Master Plan but was changed to more closely resemble the GIWW alignment. Same environmental concerns as G-2 and G-3; dropped from State Master Plan. PU2-WBI-2 Pass PU2-G-State Fail Tier 2 – Initial Hydromodeling of Structural Measures In addition to the initial screening evaluation, additional hydromodeling was necessary to resolve and further refine the possible structural measures. Remaining formulation issues included: • • • • • Non-overtopping versus weir designs for the GIWW and Highway 90 alignments. Comparison of GIWW, Highway 90 and swamp alignments. Potential impacts to Plaquemines and Larose to Golden Meadow areas. Inclusion or exclusion of Lafitte and Des Allemands (provide structural or nonstructural risk reduction). Design level of risk reduction. For this tier, non-overtopping barrier versus weir and the three alignments were evaluated (resulting in the elimination of the Highway 90 and the Swamp alignments and the creation of the Ridge alignment). During this step, a range of alignments were formulated to address the remaining formulation issues. With the inclusion of different levels of risk reduction, naming conventions for the structural measures were revised slightly from previous screening nomenclature. Table 11 describes the coding. Table 11. Planning Unit 2 Codes used for Tier 2 and Tier 3 Screening Code PU2-WBI-R-G-100-400-1000-1 -2 -3 -4 Measure Code Description (e.g. PU2-WBI-100-1) Planning Unit 2 West Bank Interior Plan. Ridge Alignment Plan GIWW Alignment Plan 100-year design level 400-year design level 1000-year design level All PU2 primary alignments include West Bank and Vicinity levees with new sector gate and Larose to Golden Meadow levees. Primary alignments for ‘R’ and ‘G’ also include Lafitte ring levees. Primary alignment plus Boutte levee. Primary alignment plus Boutte and Des Allemands levee. Primary alignment plus Boutte, Des Allemands, and Bayou Lafourche levees. 25 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Full Barrier vs. Weir Options The non-overtopping versus weir designs for the GIWW and Highway 90 alignments were evaluated using the surge maps produced by the hydromodels. Based on the surge level results, the weir alignments in Planning Unit 2 would be more cost effective since they perform nearly as well as their non-overtopping counterparts but would cost substantially less. In addition, the weir options have less direct and indirect wetland impacts and less constructability issues due to poor soil conditions. The weir options also minimize increases in water surface elevations along Plaquemines and Larose to Golden Meadow levees compared to the non-overtopping barriers. Combining the Swamp and Highway 90 Alignments into the Ridge Alignment As a result of the hydromodeling, which revealed that the estimated storm surge for the 1000year event does not impact areas of concentrated assets beyond Highway 90, the swamp alignment and Highway 90 alignments were found to be unnecessary for risk reduction and were therefore modified to follow the natural ridges and portions of Highway 90. This reformulated alignment is referred to as the Ridge Alignment. Figure 12 depicts an example Ridge alignment. A separate analysis was also done for structural improvements for the Lafitte area and was added as an increment to the GIWW and Ridge alignment plans. Figure 12. Reformulated Ridge Alignment 26 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix The remaining formulation issues would be addressed in subsequent screening (Tier 3) or in the case of structural versus nonstructural risk reduction, as part of the MCDA conducted after the structural measures are combined with nonstructural and restoration measures. Tier 3 – Final Screening of Structural Alternatives The Planning Unit 2 structural measures were then subjected to analysis using 100, 400, and 1000-year events. This resulted in the development of three variations of the West Bank Interior, six variations of the GIWW and nine variations of the Ridge Alignment. These structural measures were then ranked using the multiple attributes previously described in Table 1. Table 12 displays the ranking of the 18 measures and the screening attribute values used to conduct the ranking. 27 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Table 12. Planning Unit 2 Ranking of Measures Measure Cost Effectiveness Annual Equiv. Flood Damages Screening Attributes 2075 Pop. Present Value Impacted 400-yr Costs Event Construction Period Direct ImpactWetlands Total Value Score*** Rank Ratio* Value** $ Million Value** # People Value** $ Million Value** Years Value** Acres Value** G-100-1 13.83 0.23 510 0.70 174,599 0.43 6,281 0.18 11 0.85 969 0.10 2.49 1 WBI-100-1 2.79 0.05 725 1.00 398,872 0.99 750 0.02 6 0.46 0 0.00 2.52 2 G-100-4 21.47 0.35 435 0.60 178,505 0.44 11,509 0.33 11 0.85 2,241 0.24 2.80 3 R-100-2 9.31 0.15 684 0.94 403,309 1.00 2,849 0.08 11 0.85 704 0.07 3.10 4 R-100-3 13.89 0.23 635 0.88 403,309 1.00 4,937 0.14 11 0.85 993 0.10 3.20 5 R-100-4 19.78 0.32 613 0.85 403,012 1.00 7,461 0.21 11 0.85 1,635 0.17 3.40 6 WBI-400-1 40.16 0.65 588 0.81 168,022 0.42 15,751 0.45 12 0.92 3,688 0.39 3.65 7 R-400-2 41.08 0.67 540 0.74 159,309 0.40 17,966 0.51 13 1.00 4,392 0.46 3.79 8 R-400-3 41.43 0.67 487 0.67 150,132 0.37 20,233 0.58 13 1.00 4,687 0.50 3.79 9 R-400-4 44.66 0.73 462 0.64 144,021 0.36 22,906 0.66 13 1.00 5,323 0.56 3.94 10 G-400-1 46.68 0.76 485 0.67 142,734 0.35 22,591 0.65 12 0.92 6,161 0.65 4.00 11 WBI-1000-1 54.07 0.88 578 0.80 161,006 0.40 21,727 0.62 13 1.00 5,152 0.54 4.24 12 G-400-4 50.14 0.82 400 0.55 119,794 0.30 28,438 0.81 13 1.00 7,433 0.79 4.26 13 R-1000-3 53.15 0.86 476 0.66 142,402 0.35 26,518 0.76 13 1.00 6,146 0.65 4.28 14 R-1000-2 53.96 0.88 530 0.73 151,579 0.38 24,141 0.69 13 1.00 5,857 0.62 4.30 15 R-1000-4 55.99 0.91 452 0.62 135,800 0.34 29,250 0.84 13 1.00 6,787 0.72 4.43 16 G-1000-1 G-1000-4 57.81 61.46 0.94 1.00 484 399 0.67 0.55 141,362 117,457 0.35 0.29 28,061 34,927 0.80 1.00 12 13 0.92 1.00 8,186 9,458 0.87 1.00 4.55 4.84 17 18 Indicates structural measure is included in the overall set of LACPR alternatives to be evaluated. * Cost Effectiveness Ratio = Total Present Value Costs /Average Annual Equivalent Risk Reduction ** Value is the normalized value for the attribute where a value of 1.00 represents the greatest is the largest (lower is better) ***Total of Normalized Values (lower is better) 28 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Based on the ranking above and in consideration of the need to investigate a range of different ways to reduce the risk of hurricane storm damages the following 13 structural measures were selected (listed in order of rankings): G-100-1: This measure ranked 1st among the structural measures in Planning Unit 2. This measure, although not the cheapest, provides flood risk reduction to the greatest number of people among all 100-year measures. WBI-100-1: This measure ranked 2nd among the structural measures in Planning Unit 2 and is the least expensive of all measures. G-100-4: This measure ranked 3rd among the structural measures in Planning Unit 2. Although considerably more expensive than the previous two measures (WBI-100-1 and G-100-1), it reduces average annual flood damages to levels comparable (and in most cases more efficiently) to the 400 and 1000-year measures. R-100-2: This measure ranked 4th among the structural measures in Planning Unit 2. It is the least costly ridge alignment (modified swamp and Highway 90 alignments) measures. R-100-3: This measure ranked 5th among the structural measures in Planning Unit 2. R-100-4: This measure ranked 6th among the structural measures in Planning Unit 2. This measure provides the greatest protection among the 100-year ridge alignment measures. WBI-400-1: This measure ranked 7th among the structural measures in Planning Unit 2 and is the least costly 400-year measure. R-400-2: This measure ranked 8th among the structural measures in Planning Unit 2. R-400-3: This measure ranked 9th among the structural measures in Planning Unit 2. R-400-4: This measure ranked 10th among the structural measures in Planning Unit 2. This measure provides the greatest risk reduction among the 100-year Ridge Alignment measures. WBI-1000-1: This measure ranked 12th among the structural measures in Planning Unit 2 and is the least costly 1000-year measure. R-1000-4: This measure ranked 16th among the structural measures in Planning Unit 2 and was selected for comparison purposes with the other 1000-year measures. G-1000-4: This measure ranked last among the structural measures in Planning Unit 2. This structural measure provides the greatest risk reduction in terms of average annual damages prevented and the number of people impacted by flooding from a hurricane event. 29 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Structural Measures to be Included in Planning Unit 2 Alternatives Below are descriptions of the measures to be included as structural components of alternatives to be considered for detailed analysis for Planning Unit 2. These structural measures allow for comparison of further improvements to the existing West Bank, as well as, detailed comparison of the GIWW versus Ridge alignments (at similar levels and areas of risk reduction) for 100year, 400-year and 1000-year levels of risk reduction. For the Planning Unit 2 alternatives, these structural components have been combined with coastal restoration and nonstructural measures to provide comprehensive risk reduction. West Bank Interior Levee Alignments: WBI-100-1: This structural option targets a 100-year level of risk reduction. The only new feature in this option involves an improvement to the existing West Bank and Vicinity project, which would be to add Sector Gate South on Bayou Barataria to keep surge from entering the existing interior canals on the West Bank of Metro New Orleans. This option assumes that the existing Larose to Golden Meadow ring levee which is authorized at a 100-yr level of risk reduction will be raised to the new 100-year design heights as part of the baseline condition. WBI-400-1: This structural option is similar to WBI-100-1 but targets a 400-year level of risk reduction. This option also includes raising the Larose to Golden Meadow ring levee to 400-year design heights. WBI-1000-1: This structural option is similar to WBI-100-1 but targets a 1000-year level of risk reduction. This option also includes raising the Larose to Golden Meadow ring levee to 1000year design heights and ring levee that provides 100-year level of risk reduction for Laffite. Ridge Levee Alignments: R-100-2: This structural option targets a 100-year level of risk reduction. This structural option builds on WBI-100-1 but also includes extending the existing West Bank and Vicinity levee along the edge of development to include the Luling/Boutte area. Further, this option includes 100-year level of risk reduction to the Laffite through a series of four ring levees (Crown Point, Jean Laffite, Laffite, and Barataria) known collectively as the Lafitte ring levees. R-100-3: This structural option targets a 100-year level of risk reduction. This structural option builds on and includes the same features as R-100-2 but also includes extending the existing Larose to Golden Meadow levees along the edge of development to include communities along Bayou Lafourche south of Highway 90 and Lafitte ring levees would be raised to the 100-year level. R-100-4: This structural option targets a 100-year level of risk reduction. This structural option builds on and includes the same features as R-100-2 but also includes extending the existing Larose to Golden Meadow levees along the edge of development to include communities along Bayou Lafourche south of Highway 90. In addition, existing Des Allemands and Lafitte ring levees would be raised to the 100-year level. 30 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix R-400-2: This structural option targets a 400-year level of risk reduction. This structural option contains the same features at R-100-2 but all levees would be raised or built to the 400-year level with the exception of the Lafitte ring levees which would be raised to the 100-year level. R-400-3: This structural option targets a 400-year level of risk reduction. This structural option contains the same features at R-100-3 but all levees would be raised or built to the 400-year level with the exception of the Lafitte ring levees which would be raised to the 100-year level. R-400-4: This structural option targets a 400-year level of risk reduction. This structural option includes the same features as R-100-4 but involves building those levees at a 400-year design height (except the Lafitte ring levees which would be at the 100-year design) as well as raising existing levees on the West Bank of New Orleans and the existing Larose to Golden Meadow ring levee to a 400-year design height. R-1000-4: This structural option targets a 1000-year level of risk reduction. This structural option includes the same features as R-100-4 and R-400-4 but involves building those levees at a 1000-year design height (except the Lafitte ring levee which would be at the 100-year design) as well as raising existing levees on the West Bank of New Orleans and the existing Larose to Golden Meadow ring levee to a 1000-year design height. GIWW Levee Alignments: G-100-1: This structural option targets a 100-year level of risk reduction. This option builds on and includes the same features as WBI-100-1 and also consists of a surge reduction barrier in the form of a 12.5-foot elevation weir that roughly follows the GIWW, which already acts as a partial barrier. Structures would consist of sixteen 50-foot tainter gates, a 110-foot sector gate on Bayou Perot, and a 110-foot lock on Bayou Barataria and ring levees that provides 100-year level of risk reduction for Laffite G-100-4: This structural option targets a 100-year level of risk reduction. The option includes the same new levee alignments as described in R-100-4 but also includes the 12.5-foot elevation surge reduction barrier weir that is described in G-100-1. G-1000-4: This structural option targets a 1000-year level of risk reduction. The option includes the same weir and levees described in G-100-4 but levees would be at the 1000-year design height. Special Case: Lower Plaquemines Parish Plaquemines Parish, which is split roughly in half by the Mississippi River, lies in both Planning Units 1 and 2. The portion of Plaquemines Parish on the east side of the Mississippi River is contained in Planning Unit 1 and the west side is contained in Planning Unit 2. Because of its unique nature, the portions of Plaquemines Parish below Belle Chasse are handled as a special case for plan formulation. 31 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Tier 1 – Initial Screening of Structural Alignments The Plan Formulation Atlas presented four options for increased risk reduction in Plaquemines Parish: 1. Ring Levees/Spillways (PL-RS) – This option proposes spillways in combination with ring levees in multiple locations in Plaquemines Parish. The spillway concept was envisioned to reduce hurricane surge in the New Orleans area and Plaquemines Parish by degrading sections of the existing Plaquemines Parish levees to allow storm surge transfer between Breton Sound and Barataria Bay areas. Highway bridges would be constructed over degraded levee reaches. 2. Closed Ring Levee System (PL-RL) – This option includes a series of basins (ring levees) that would provide an increased level of risk reduction to critical facilities and more densely populated areas of lower Plaquemines Parish. Levee sections outside the closed ring levee areas would remain at existing height. 3. Federal Levee Alignment (PL-FL) – This option proposes to raise the height of all Federal levees in lower Plaquemines Parish to the 100-year design level and to leave the non-Federal levees at existing height. 4. Existing Levee Alignment (PL-EL) – This option would incorporate non-Federal levees in Plaquemines Parish into the Federal levee system and raise the height of all existing levees in lower Plaquemines Parish. Figure 13 displays the ring levee/spillway concept in Plaquemines Parish. Note: The location and width of spillways is purely conceptual. For the hydromodeling evaluation used in the Tier 2 screening only three spillways were considered. Figure 13. Plaquemines Ring Levee/Spillway Concept from the Plan Formulation Atlas 32 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Following hurricanes Katrina and Rita, the USACE conducted a study to provide risk reduction though structural measures in lower Plaquemines Parish. Specifically, two options that provide 100-year level of risk reduction were developed for that study. These options include: 1. Creation of ring levees around the most populated portions of the Parish (estimated cost of roughly $3.6 billion) and 2. Providing 100-year risk reduction to the entire lower Plaquemines Parish by raising and armoring existing levees (estimated cost of roughly $5.8 billion). As a result of the high cost and the potential surge increase in Louisiana and Mississippi created by levees in this area, both the State Master Plan stakeholder process and the USACE screening process eliminated most of the structural measures in lower Plaquemines Parish. Table 13 summarizes the results of the Tier 1 screening. Table 13. Screening Results for Lower Plaquemines Parish Measure Code(s) PL-RS Pass/Fail Pass PL-RL Fail PL-FL Fail PL-EL Fail Comments Spillway concept carried forward pending hydromodeling results to evaluate regional benefits. Excessively high costs; constructability issues; lack of stakeholder support; transportation access issues (would require elevated roadways connecting areas inside and outside the ring levees). Excessively high costs; constructability issues; lack of stakeholder support. Excessively high costs; constructability issues. Tier 2 – Initial Hydromodeling of Structural Measures In order to understand the influence of the Mississippi River levees and adjacent back levees in lower Plaquemines Parish, the following two cases were modeled: 1. The creation of three spillways (totaling 9.5 miles) across the lower Mississippi River; 2. The removal of all levees (totaling 57 miles) along the Mississippi River within the delta which allows the relatively free flow of water across the Mississippi River. This analysis was designed to understand how surge builds up along these levees from Breton Sound and propagates towards New Orleans and Baton Rouge in the Mississippi River. In addition, the effectiveness of building localized ring levees to provide a higher level of risk reduction in lower Plaquemines Parish can be ascertained. The first case described above for the spillway concept did not produce significant regional reductions in water levels. The second case (tearing down all levees) did produce some reductions in regional water levels; however, this approach would not likely be acceptable. In general, the results are inconclusive for making a recommendation at this time. The spillway concept appears to have some merit but further study is needed; therefore, the spillway option was not carried forward as a risk reduction measure for LACPR. 33 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Planning Unit 3a The following sections provide details on the tiered screening of structural measures and alignments for Planning Unit 3a. Planning Unit 3a begins in Baton Rouge and continues south along the Mississippi River and Bayou Lafourche to the Gulf of Mexico. The boundary then extends westward to Bayou de West, and then generally follows Bayou de West north to Interstate Highway 10 and back to Baton Rouge. The Planning Unit consists of Terrebonne, St. Mary (East Bank), Lafourche (West Bank), Assumption (West Bank), and St. Martin (East Bank) Parishes. This planning unit includes approximately 249,000, or 12 percent, of the population within the overall planning area. Communities at risk in this Planning Unit include a portion of the Baton Rouge metropolitan area as well Bayou Cane, Houma, Morgan City, Raceland and Thibodaux among others. This planning unit contains infrastructure assets in and around population centers, consisting of oil and gas infrastructure, marinas, and port facilities. Tier 1 – Initial Screening of Structural Alignments The Plan Formulation Atlas identified three primary strategies for structural risk reduction in Planning Unit 3a. They include a GIWW alignment (Figure 14), a Morganza to the Gulf alignment (Figure 15) and an Atchafalaya Backwater alignment (Figure 16). The alignments proposed in PU3a would provide flood risk reduction to Lockport, Raceland, Houma, Thibodaux and Morgan City, among others. The GIWW alignment would consist of a new levee along the GIWW from Larose to Morgan City or to Thibodaux with a ring levee around Morgan City. The Morganza to the Gulf alignment proposes to add a levee using the Morganza to the Gulf alignment from Larose to Morgan City or Thibodaux with a ring levee around Morgan City. The Atchafalaya Backwater alignment would consist of a new levee around the backwaters of the Atchafalaya including ring levees and the recently authorized Morganza to the Gulf levee alignment. Within these three strategies, the Plan Formulation Atlas identified six variations including an alignment identified in the State Master Plan. Table 14 describes the codes used in the Plan Formulation Atlas and for Tier 1 screening for measures in Planning Unit 3a. Table 14. Planning Unit 3a Codes from Plan Formulation Atlas used for Tier 1 Screening Code PU3a-M-G-AB -State -# Measure Code Description (e.g. PU3a-G-1) Planning Unit 3a Morganza levee alignment GIWW levee alignment with Morganza Levee at 100-year design Atchafalaya backwater alignment Alignment that was part of the preliminary draft State Master Plan Variations to the primary alignments (if applicable) Figures 14 through 16 show examples of the various structural measure alignments. 34 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Figure 14. Example GIWW Alignment from the Plan Formulation Atlas Figure 15. Example Morganza to the Gulf Alignment from the Plan Formulation Atlas 35 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Figure 16. Atchafalaya Backwater Alignment from the Plan Formulation Atlas Through the first tier of screening, in which preliminary construction costs, constructability as well as direct environmental impacts were considered, the number of variations was screened to three. Table 15 lists the variations of the levee alignments and describes why some alignment variations were eliminated from further consideration at this time. 36 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Table 15. Initial Screening of Planning Unit 3a Structural Measures Measure Code(s) PU3a-G-1 Pass/Fail Comments Pass PU3a-G-2 Pass PU3a-M-1 Fail PU3a-M-2 Fail PU3a-AB PU3a-State Fail Pass Similar to GIWW alignment in SMP; works well with bypass channel identified in the coastal restoration measures. The levee may only have to be built to 10 or 15 feet. Related to Morganza to the Gulf tie back associated with new 100year surge data. This option may be incomplete because it would require parts of PU3a-AB to be implemented. Excessive costs; doesn’t prevent flooding from hurricane surge and wave run-up. Excessive costs; doesn’t prevent flooding from hurricane surge and wave run-up. Excessive costs Similar to G-1 but includes additional alignment from Golden Meadow to Pointe au Chene that will likely be screened out due to environmental concerns and poor soil conditions (higher cost/mile). Bayou DuLarge levee alignment creates a surge amplification. Tier 2 – Initial Hydromodeling of Structural Measures In addition to the initial screening evaluation, additional hydromodeling was necessary to resolve and further refine the possible structural measures in Planning Unit 3a. Remaining formulation issues included: • • • Comparison of the various GIWW alignments. A continuous levee or a ring levee for Morgan City. Design level of risk reduction. The hydromodeling revealed that the measures from the Plan Formulation Atlas needed to be reformulated based on areas impacted and the location of concentrated assets. This resulted in three structural measures including: • • • A continuous levee from Larose in the east to Morgan City in the west then north where it will tie into the ridge following the Bayou Black. This alignment is similar to the recently authorized Morganza levee (Figure 17). Modification to the Morganza Alignment by tying back the Morganza levee to high ground south of Thibodaux. This measure includes a ring levee around Morgan City (Figure 18). This measure is the same as described in the previous bullet but it includes a levee along the GIWW to create a secondary line of defense (Figure 19). 37 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Figure 17. Reformulated Morganza Levee Alignment with Tie-in West of Morgan City Figure 18. Reformulated Morganza Levee Alignment with Morgan City Ring Levee 38 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Figure 19. Reformulated GIWW Alignment With the inclusion of different levels of risk reduction, name convention for the structural managements measures were revised slightly from previous screening nomenclature. Table 16 describes the coding. Table 16. Planning Unit 3a Codes used for Tier 2 and Tier 3 Screening Code PU3a-M-G-100-400-1000-1 -2 Measure Code Description (e.g. PU3a-M-100-1) Planning Unit 3a Morganza Levee alignment GIWW Alignment Plan with Morganza Levee at 100-year design 100-year design level 400-year design level 1000-year design level Morganza alignment with tieback to high ground west of Morgan City Morganza alignment with tieback to high ground south of Thibodaux and ring levee around Morgan City 39 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Tier 3 – Final Screening of Structural Alternatives The Planning Unit 3a structural measures were then subjected to analysis using 100, 400, and 1000-year events. This resulted in the development of six variations of the Morganza Levee alignment and two variations of the GIWW alignments. These structural measures were then ranked using the multiple attributes previously described in Table 1. Table 17 displays the ranking of the eight measures and the screening attribute values used to conduct the ranking. 40 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Table 17. Planning Unit 3a Ranking of Measures Measure Cost Effectiveness Annual Equiv. Flood Damages Screening Attributes 2075 Pop. Present Value Impacted 400-yr Costs Event Construction Period Direct ImpactWetlands Total Value Score*** Rank Ratio* Value** $ Million Value** # People Value** $ Million Value** Years Value** Acres Value** G-400-2 15.50 0.36 1,184 0.84 51,913 0.43 20,207 0.44 10 0.71 5,261 0.62 3.41 1 G-1000-2 16.67 0.39 1,169 0.83 50,809 0.42 21,978 0.48 10 0.71 6,642 0.79 3.62 2 M-100-1 13.82 0.32 1,207 0.86 100,745 0.83 17,701 0.38 10 0.71 4,880 0.58 3.69 3 M-100-2 12.08 0.28 1,212 0.86 121,307 1.00 15,405 0.33 10 0.71 4,201 0.5 3.69 4 M-400-2 23.53 0.55 1,285 0.91 34,879 0.29 28,290 0.61 12 0.86 6,128 0.73 3.95 5 M-400-1 27.45 0.64 1,290 0.92 27,229 0.22 32,870 0.71 12 0.86 7,639 0.91 4.26 6 M-1000-2 35.98 0.84 1,401 1.00 33,590 0.28 39,070 0.85 14 1.00 6,313 0.75 4.71 7 M-1000-1 42.61 1.00 1,406 1.00 26,429 0.22 46,087 1.00 14 1.00 8,425 1.00 5.22 8 Indicates structural measure is included in the overall set of LACPR alternatives to be evaluated. * Cost Effectiveness Ratio = Total Present Value Costs /Average Annual Equivalent Risk Reduction ** Value is the normalized value for the attribute where a value of 1.00 represents the greatest is the largest (lower is better) ***Total of Normalized Values (lower is better) 41 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Based on the ranking above and in consideration of the need to investigate a range of different ways to reduce the risk of hurricane storm damages the following four structural measures were selected for the final array (listed in order of rankings): G-400-2: This measure ranked 1st among the structural measures in Planning Unit 3a. It is the least costly among the measures designed to provide protection against the 400-year hurricane event. G-1000-2: This measure ranked 2nd among the structural measures in Planning Unit 3a. It is the least costly among the measures designed to provide protection against the 1000-year hurricane event. M-100-1: This measure ranked 3rd among the structural measures in Planning Unit 3a. This measure is the 2nd cheapest among PU3 structural measures but impacts twice as many people than any of the 3 previous measures. M-100-2: This measure ranked 4th among the structural measures in Planning Unit 3a. This measure is the most cost effective among PU3a structural measures and is the least costly, however, it provides hurricane surge protection to the fewest people. The remaining structural measures in PU3a, ranked 5th – 8th, were eliminated do to the extremely high costs. Structural Measures to be included in Planning Unit 3a Alternatives Below is the array of options to be included as structural components of alternatives to be considered for detailed analysis for Planning Unit 3a. These structural measures allow for comparison of risk reduction improvements to Houma, Morgan City and other communities in Planning Unit 3a for 100-year, 400-year and 1000-year levels of risk reduction. For the Planning Unit 3a alternatives, these structural components are combined with coastal restoration and nonstructural measures to provide comprehensive risk reduction. Morganza to the Gulf Levee Alignments: M-100-1: This structural option targets a 100-year level of risk reduction. This option involves constructing the Morganza to the Gulf levee with extension tying into high ground west of Morgan City at 100-year design level. M-100-2: This structural option targets a 100-year level of risk reduction. This option involves construct a portion of the Morganza to the Gulf levee from Larose west to a tieback to high ground south of Thibodaux. Included in this option is a ring levee around Morgan City at 100year design level. GIWW Levee Alignments: G-400-2: This structural option targets a 400-year level of risk reduction. This option involves construct a portion of the Morganza to the Gulf levee from Larose west to a tieback to high ground south of Thibodaux at 100-year design level. A secondary levee would be constructed 42 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix along the GIWW that provides 400-year level of risk reduction. Included in this option is a ring levee around Morgan City that provides 400-year level of risk reduction. G-1000-2: This structural option targets a 1000-year level of risk reduction. This option involves construct a portion of the Morganza to the Gulf levee from Larose west to a tieback to high ground south of Thibodaux at 100-year design level. A secondary levee would be constructed along the GIWW that provides 1000-year level of risk reduction. Included in this option is a ring levee around Morgan City that provides 1000-year level of risk reduction. Planning Unit 3b The following sections provide details on the tiered screening of measures and alignments for Planning Unit 3b. The planning unit extends from Bayou de West westward to Freshwater Bayou with Interstate Highway 10 forming the northern boundary and the southern boundary formed by the Gulf. The western boundary falls just to the west of the coastal wetlands, Abbeville and Lafayette, covering all or part of Terrebonne, St. Mary, Iberia, and Vermilion Parishes. This planning unit includes a population of about 350,000, which represents approximately 16 percent of the population within the planning area. It includes the cities and towns of Berwick, Patterson, Franklin, Jeanerette, New Iberia, Abbeville, Garden City, Sorrel, Louisa, Avery Island, Delcambre, Erath, Henry, Intracoastal City, and others, as well as the southern portion of Lafayette. Most of the area population is located along Bayou Teche. This planning unit contains infrastructure assets in and around population centers, consisting of oil and gas infrastructure, marinas, and port facilities. Tier 1 – Initial Screening of Structural Alignments The Plan Formulation Atlas presented two primary strategies for structural risk reduction in Planning Unit 3b. They include an alignment along the GIWW and the Franklin to Abbeville alignment which is inland from the GIWW. Within these two strategies, the Plan Formulation Atlas presented four variations. Table 18 describes the codes used for Tier 1 screening of measures in Planning Unit 3b. Figure 20 and Figure 21 show examples of the various alignments. Table 18. Planning Unit 3b Codes from Plan Formulation Atlas used for Tier 1 Screening Code PU3b-G-FA-State -# Measure Code Description (e.g. PU3b-G-1) Planning Unit 3b GIWW levee alignment Franklin to Abbeville alignment (inland of the GIWW) Alignment that was part of the preliminary draft State Master Plan Variations to the primary alignments (if applicable) 43 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Figure 20. Example GIWW Alignment from the Plan Formulation Atlas Figure 21. Example Franklin to Abbeville Alignment from the Plan Formulation Atlas 44 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Through the first tier of screening, in which preliminary construction costs, constructability as well as direct environmental impacts were considered, the number of variations was screened to three. Table 19 lists the variations of the levee alignments and describes why some alignment variations were eliminated from further consideration at this time. Table 19. Initial Screening of Planning Unit 3b Structural Measures Measure Code(s) PU3b-G-1 Pass/Fail PU3b-G-2 Fail PU3b-FA and PU3bState Pass Pass Comments Alignment that forms part of a continuous levee across all of South Louisiana. Captured in alignments ‘G-1’ and ‘FA.’ When comparing the ‘G2’ alignment to the ‘FA’ alignment, ‘FA’ is the preferred alignment. The Franklin to Abbeville (FA) alignment is essentially same as the State Master Plan alignment. Tier 2 – Initial Hydromodeling of Structural Measures In addition to the initial screening evaluation, additional hydromodeling was necessary to resolve and further refine the possible structural measures in Planning Unit 3b. Remaining formulation issues included: • • • Comparison of the GIWW and the Franklin to Abbeville alignment. Formulation of additional structural measures due to the dispersed population with isolated areas of higher density. Design level of risk reduction. As a result of the high cost of a continuous levee (GIWW and Franklin to Abbeville alignments), a measure that includes a series of ring levees rather than a continuous levee was considered and evaluated. This resulted in a measure with ring levees in the west to protect the major population centers, with a continuous levee from Baldwin and across to the east. As a result of Tier 2 screening, the following three types of measures were carried to Tier 3: • The GIWW alignment (similar to Figure 20); • The Franklin to Abbeville alignment (similar to Figure 21); • A series of ring levees around Patterson/Berwick, Franklin/Baldwin, New Iberia, Erath, Delcambre, and Abbeville (see Figure 22 below). 45 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Figure 22. Reformulated Ring Levee Alignment With the inclusion of different risk-reduction levels, name convention for the structural managements measures were revised slightly from previous screening nomenclature. Table 20 describes the coding. Table 20. Planning Unit 3b Codes used for Tier 2 and Tier 3 Screening Code PU3b-G-F-RL-100-400-1000-1 Measure Code Description (e.g. PU3b-RL-100-1) Planning Unit 3b GIWW levee alignment Franklin to Abbeville alignment (inland of the GIWW) Ring levee alignment 100-year design level 400-year design level 1000-year design level Primary alignment for each plan strategy. 46 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Tier 3 – Final Screening of Structural Alternatives The Planning Unit 3b structural measures were then subjected to analysis using 100, 400, and 1000-year events. This resulted in the development of nine variations. These structural measures were then ranked using the multiple attributes previously described in Table 1. Table 21 displays the ranking of the nine measures and the screening attribute values used to conduct the ranking. 47 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Table 21. Planning Unit 3b Ranking of Measures Screening Attributes Measure Cost Effectiveness Equiv. Annual Flood Damages 2075 Pop. Impacted 400-yr Event Present Value Costs Construction Period Direct Impact- Wetlands Total Value Score*** Rank Ratio* Value** $ Million Value** # People Value** $ Million Value** Years Value** Acres Value** G-100-1 33.61 0.35 353 0.64 11,793 0.16 13,876 0.47 10 0.71 2,296 0.29 2.62 1 F-100-1 35.48 0.37 411 0.75 67,980 0.90 12,589 0.43 10 0.71 2,466 0.31 3.46 2 F-400-1 62.15 0.64 411 0.75 8,053 0.11 22,069 0.75 12 0.86 3,878 0.49 3.58 3 G-400-1 56.14 0.58 385 0.70 2,964 0.04 21,403 0.73 12 0.86 5,506 0.69 3.59 4 RL-100-1 43.93 0.45 528 0.96 75,917 1.00 10,433 0.35 10 0.71 940 0.12 3.60 5 RL-400-1 71.63 0.74 529 0.96 40,911 0.54 16,966 0.57 12 0.86 1,702 0.21 3.89 6 F-1000-1 91.07 0.94 444 0.81 7,706 0.10 29,280 0.99 14 1.00 5,188 0.65 4.49 7 RL-1000-1 97.13 1.00 549 1.00 38,308 0.50 21,092 0.71 14 1.00 2,218 0.28 4.50 8 G-1000-1 85.63 0.88 421 0.77 2,870 0.04 29,519 1.00 14 1.00 7,987 1.00 4.69 9 Indicates structural measure is included in the overall set of LACPR alternatives to be evaluated. * Cost Effectiveness Ratio = Total Present Value Costs /Average Annual Equivalent Risk Reduction ** Value is the normalized value for the attribute where a value of 1.00 represents the greatest is the largest (lower is better) ***Total of Normalized Values (lower is better) 48 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Based on the ranking above and in consideration of the need to investigate a range of different ways to reduce the risk of hurricane storm damages the following four structural measures were selected for the final array (listed in order of rankings): G-100-1: This measure ranked 1st among the structural measures in Planning Unit 3b. This measure performed considerably better than the other structural measures in PU3b. Although it is not the least cost, it was the most cost effective and protected the greatest number of people. F-100-1: This measure ranked 2nd among the structural measures in Planning Unit 3b. This measure is less costly than G-100-1 but protects less people. F-400-1: This measure ranked 3rd among the structural measures in Planning Unit 3b. This measure ranked highest among all the measures designed to provide protection against the 400year hurricane event G-400-1 was more cost effective and protected more people, but the impacts to wetlands was much greater. RL-100-1: This measure ranked 5th among the structural measures in Planning Unit 3b. This measure has the least cost and has the least impact to wetlands. RL-400-1: This measure ranked 6th among the structural measures in Planning Unit 3b. This measure is included to provide a comparison between the management measures F-1000-1: This measure ranked 7thamong the structural measures in Planning Unit 3b. This measure is the highest ranking measure designed to that provide protection against the 1000-year hurricane event, however it is not the least expensive. Structural Measures to be included in Planning Unit 3b Alternatives Below is the array of options to be included as structural components of alternatives to be considered for detailed analysis for Planning Unit 3b. These structural measures allow for comparison of risk reduction improvements in Planning Unit 3b. These structural components will be combined with coastal restoration and nonstructural measures to provide comprehensive risk reduction. Continuous Levee Alignments: G-100-1: Raise ring levee around Patterson/Berwick to 100-year design level and construct levee along the GIWW west to the boundary of Planning Unit 4 at the 100-year design level. F-100-1: Raise ring levee around Patterson/Berwick to 100-year design level and construct levee along the edge of development north of the GIWW to high ground west of Abbeville at the 100year design level. F-400-1: Raise ring levee around Patterson/Berwick to 400-year design level and construct levee along the edge of development north of the GIWW to high ground west of Abbeville at the 400year design level. 49 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix F-1000-1: Raise ring levee around Patterson/Berwick to 1000-year design level and construct levee along the edge of development north of the GIWW to high ground west of Abbeville at the 1000-year design level. Ring Levee Alignments: RL-100-1: Raise ring levee around Patterson/Berwick to 100-year design level and construct ring levees around Franklin/Baldwin, New Iberia, Erath, Delcambre, and Abbeville at the 100year design level. RL-400-1: Raise ring levee around Patterson/Berwick to 400-year design level and construct ring levees around Franklin/Baldwin, New Iberia, Erath, Delcambre, and Abbeville at the 400year design level. Planning Unit 4 The following sections provide details on the tiered screening of measures and alignments for Planning Unit 4. Planning Unit 4 extends from the western bank of Freshwater Bayou westward to the Louisiana/Texas state line in Sabine Lake, and from the Gulf of Mexico in the south to the northern boundary located just north of Sulphur, Lake Charles, and Interstate Highway 10. The planning unit includes all or parts of Vermilion, Cameron, Acadia, Jefferson Davis, and Calcasieu Parishes. The Chenier Plain extends from Freshwater Bayou westward to Sabine Pass, and is influenced by three interconnected rivers and marine processes. There are two major hydrologic basins in the Cheniers: the Mermentau Basin and the Calcasieu/Sabine Basin. The navigation channels of the Chenier Plain are the Sabine/Neches Waterway, Calcasieu River Navigation Channel, the GIWW, Mermentau Ship Channel, and Freshwater Bayou Canal, and all of them influence hydrology throughout the planning unit. This planning unit represents approximately 250,000 residents, or 12 percent of the population, within the planning area. Major population centers within the planning unit include Duson, Rayne, Crowley, Estherwood, Mermentau, Jennings, Welsh, Iowa, Lake Charles, Sulphur, Vinton, Kaplan, Morse, and Lake Arthur. Significant oil and gas facilities, chemical plants, and other coast-related industries are located in the Lake Charles area, Lafayette, Hackberry, Vinton, and smaller communities. Agricultural land and cattle land are the primary land uses in much of Planning Unit 4. Tier 1 – Initial Screening of Structural Alignments Five primary strategies were identified for structural risk reduction in Planning Unit 4. They include ring levees, GIWW alignment, Highway 82 alignment, ten-foot contour alignment and the State Master Plan alignment. The ring levees provide risk reduction to concentrated assets in communities such as Abbeville, Kaplin, Vinton, Sulphur, Westlake, Lake Charles and Gueydon. The GIWW alignment would provide a continuous levee from Patterson/Berwick to Abbeville along the GIWW while the Highway 92 alignment would provide a continuous levee along the highway from Vinton to Abbeville. The ten-foot contour alignment would provide a nearly continuous levee along the ten-foot contour from Texas to Abbeville. The State Master Plan alignment is a hybrid between the GIWW and the Ring Levee alignments. Within these five 50 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix strategies, six variations were identified. Table 22 describes the codes used in the Plan Formulation Atlas and for Tier 1 screening for measures in Planning Unit 4. Figures 23 through 26 show examples of the various alignments. Table 22. Planning Unit 4 Codes from Plan Formulation Atlas used for Tier 1 Screening Code PU4-RL-G -H -C -State -# Measure Code Description (e.g. PU4-RL-2) Planning Unit 4 Ring levee alignment GIWW levee alignment Highway 82 alignment 10-foot contour alignment Alignment that was part of the preliminary draft State Master Plan Variations to the primary alignments (if applicable) Figure 23. Example Ring Levee Alignment from Plan Formulation Atlas 51 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Figure 24. GIWW Alignment from Plan Formulation Atlas Figure 25. Highway 82 Alignment from Plan Formulation Atlas 52 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Figure 26. 10-Foot Contour Alignment from Plan Formulation Atlas Through the first tier of screening, in which preliminary construction costs, constructability as well as direct environmental impacts were considered, the number of variations was screened to three. Table 23 lists the variations of the levee alignments and describes why some alignment variations were eliminated from further consideration at this time. Table 23. Initial Screening of Planning Unit 4 Structural Measures Measure Code(s) PU4-RL PU4-RL-2 Pass/ Fail Pass Fail PU4-G Pass PU4-H Fail PU4-C Fail PU4-State Pass Comments Consistent with State’s ring levee concept. Ring levee concept captured better by ‘RL’ above; this version has excessive costs and would exacerbate Vermilion River flooding in comparison to ‘RL.’ Forms part of a continuous levee from border to border for evaluation of a comprehensive “Category 5” structural option. Strong local opposition; high cost; environmental concerns such as wetland impacts and drainage problems (e.g. trapping saltwater after a storm). Long length (high life-cycle costs); environmental concerns such as wetland impacts and drainage problems (e.g. trapping saltwater after a storm). Hybrid approach using both a ring levee and a GIWW alignment. 53 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Tier 2 – Initial Hydromodeling of Structural Measures In addition to the initial screening evaluation, additional hydromodeling was necessary to resolve and further refine the possible structural measures in Planning Unit 4. Remaining formulation issues included: • • • Comparison of the various GIWW alignments. A continuous levee or a series of ring levees to protect isolated areas. Design level of risk reduction. The hydromodeling results revealed that the measures needed to be reformulated based on areas impacted and the location of concentrated assets. This reformulation resulted in variations on the two structural strategies, including a levee along the GIWW that runs south of the majority of population-at-risk from flooding (Figure 27 and Figure 28) and a series of site specific ring levees to protect major population centers (Figure 29). Figure 27. Reformulated GIWW Alignment (with tie in to Planning Unit 3b). 54 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Figure 28. Reformulated GIWW Alignment (stand alone for Planning Unit 4). Figure 29. Reformulated Ring Levee Alignments. 55 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix With the inclusion of different levels of risk reduction, name convention for the structural managements measures were revised slightly from previous screening nomenclature. Table 24 describes the coding. Table 24. Planning Unit 4 Codes used for Tier 2 and Tier 3 Screening Code PU4-G-RL-100-400-1000-1 -2 -3 Measure Code Description (e.g. PU4-RL-100-1) Planning Unit 4 GIWW levee alignment Ring levee alignment 100-year design level 400-year design level 1000-year design level For the ‘G’ alignments, the primary alignment follows the GIWW across the planning unit boundaries. GIWW alignment with tieback to high ground near Kaplan. GIWW alignment with the levee set at a height of 12 feet. Tier 3 – Final Screening of Structural Alternatives The Planning Unit 4 structural measures were then subjected to analysis using 100, 400, and 1000-year events. This resulted in the development of 11 variations. These structural measures were then ranked using the multiple attributes previously described in Table 1. Table 25 displays the ranking of the 11 measures and the screening attribute values used to conduct the ranking. 56 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Table 25. Planning Unit 4 Ranking of Measures Screening Attributes Cost Effectiveness Measure Equiv. Annual Flood Damages 2075 Pop. Impacted 400-yr Event Present Value Costs Construction Period Direct ImpactWetlands Total Value Score*** Rank Ratio* Value** $ Million Value** # People Value** $ Million Value** Years Value** Acres Value** RL-100-1 16.37 0.06 565 0.83 44,284 0.58 2,374 0.11 10 0.71 88 0.02 2.31 1 RL-1000-1 106.66 0.39 679 1.00 49,117 0.64 3,299 0.15 14 1.00 99 0.02 3.20 2 G-400-3 76.57 0.28 571 0.84 46,102 0.60 10,692 0.50 10 0.71 2,483 0.44 3.38 3 RL-400-1 105.38 0.39 681 1.00 76,409 1.00 3,057 0.14 12 0.86 95 0.02 3.40 4 G-100-2 75.29 0.28 568 0.83 73,948 0.97 10,736 0.50 10 0.71 1,763 0.31 3.60 5 G-100-1 73.51 0.27 562 0.83 73,304 0.96 10,907 0.51 10 0.71 2,221 0.39 3.67 6 G-400-2 111.49 0.41 567 0.83 27,530 0.36 15,946 0.74 12 0.86 2,939 0.52 3.72 7 G-400-1 109.15 0.40 562 0.82 26,439 0.35 16,209 0.75 12 0.86 3,719 0.66 3.84 8 G-1000-3 271.63 1.00 669 0.98 47,299 0.62 11,119 0.52 10 0.71 2,485 0.44 4.27 9 G-1000-2 156.40 0.58 577 0.85 26,968 0.35 20,861 0.97 14 1.00 4,277 0.76 4.50 10 G-1000-1 155.77 0.57 572 0.84 25,885 0.34 21,546 1.00 14 1.00 5,625 1.00 4.75 11 Indicates structural measure is included in the overall set of LACPR alternatives to be evaluated. * Cost Effectiveness Ratio = Total Present Value Costs /Average Annual Equivalent Risk Reduction ** Value is the normalized value for the attribute where a value of 1.00 represents the greatest is the largest (lower is better) ***Total of Normalized Values (lower is better) 57 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix Based on the ranking above and in consideration of the need to investigate a range of different ways to reduce the risk of hurricane storm damages the following seven structural measures were selected for the final array (listed in order of rankings): RL-100-1: This measure ranked 1st among the structural measures in Planning Unit 4. This management measure is the least costly and most cost effective management measure among structural measures considered. RL-1000-1: This measure ranked 2nd among the structural measures in Planning Unit 4. This management measure provides protection to a greater population than RL-100-1 at a slightly higher cost. RL-1000-1 is the most cost effective management measure among the measures designed to provide protection against the 1000-year hurricane event. G-400-3: This measure ranked 3rd among the structural measures in Planning Unit 4. This management measure is the most cost effective measure among the measures designed to provide protection against the 400-year hurricane event. RL-400-1: This measure ranked 4th among the structural measures in Planning Unit 4. Although considerably less expensive than G-400-3, this measure provides structural protection to a significantly smaller population. G-100-2: This measure ranked 5th among the structural measures in Planning Unit 4. This measure is included to provide a comparison between the management measures. G-100-1: This measure ranked 6th among the structural measures in Planning Unit 4. This measure is included to provide a comparison between the management measures. G-1000-3: This measure ranked 9th among the structural measures in Planning Unit 4. This measure is included to provide a comparison between the management measures. Structural Measures to be included in Planning Unit 4 Alternatives Below is the array of options to be included as structural components of alternatives to be considered for detailed analysis for Planning Unit 4. These structural measures allow for comparison of risk reduction improvements to communities in Planning Unit 4. For the Planning Unit 4 alternatives, these structural components will be combined with coastal restoration and nonstructural measures to provide comprehensive risk reduction. GIWW (Continuous Levee) Alignments: G-100-1: Construct a continuous levee (with gates) along the GIWW plus a ring levee to the west of the Calcasieu River and a series of levees within Lake Charles to separate the river from the land at the 100-year design level. Alignment joins with similar alignment in Planning Unit 3b. G-100-2: Construct a continuous levee (with gates) along the GIWW plus a ring levee to the west of the Calcasieu River and a series of levees within Lake Charles to separate the river from 58 Louisiana Coastal Protection and Restoration (LACPR) Final Technical Report Structural Plan Component Appendix the land at the 100-year design level. Alignment ties to high ground to the west of the Vermilion River so this alternative can be evaluated as "stand alone" from alternatives in Planning Unit 3b. G-400-3: Construct a continuous 12-foot levee (with gates) along the GIWW plus a ring levee to the west of the Calcasieu River and a series of levees within Lake Charles to separate the river from the land. Includes small ring levees around parts of Lake Charles, Gueydan, and Kaplan to provide 400-year level of risk reduction. Alignment ties to high ground to the west of the Vermilion River so this alternative can be evaluated as "stand alone" from alternatives in Planning Unit 3b. G-1000-3: Construct a 12-foot continuous levee (with gates) along the GIWW plus a ring levee to the west of the Calcasieu River and a series of levees within Lake Charles to separate the river from the land. Includes small ring levees around parts of Lake Charles, Gueydan, and Kaplan to provide 1000-year level of risk reduction. Alignment ties to high ground to the west of the Vermilion River so this alternative can be evaluated as "stand alone" from alternatives in Planning Unit 3b. Ring Levee Alignments: RL-100-1: Construct ring levees to the east and west of Lake Charles; construct a series of levees within Lake Charles to separate the river from the land; and construct ring levees around Kaplan and Gueydan to the 100-year design level. RL-400-1: Construct ring levees to the east and west of Lake Charles; construct a series of levees within Lake Charles to separate the river from the land; and construct ring levees around Kaplan and Gueydan to the 400-year design level. RL-1000-1: Construct ring levees to the east and west of Lake Charles; construct a series of levees within Lake Charles to separate the river from the land; and construct ring levees around Kaplan and Gueydan to 1000-year design level. Summary This appendix described the steps taken to screen structural risk reduction measures for the LACPR technical evaluation. The process started with a wide array of concepts gathered from previous studies as well as input from the State Master Plan and other stakeholders. The threetiered screening process first eliminated measures that were either undesirable on their own merits or in comparison to similarly performing measures. The next step was to evaluate and reformulate the remaining measures using quantitative hydromodeling data. The final screening used six attributes to rank the structural measures to determine which should be carried forward into the set of alternatives to be evaluated for the overall LACPR effort. The coastal restoration and nonstructural measures, which are part of the overall LACPR alternatives, were developed on parallel tracks. The formulation of those measures is described in the Coastal Restoration Plan Component and Environmental Metrics Appendix and Nonstructural Plan Component Appendix, respectively. 59