Mississippi River Reintroduction into Bayou Lafourche Phase 2
Mississippi River Reintroduction into Bayou Lafourche Phase 2 Design Report April 18, 2006 Coastal Restoration Team W 092004002 GN V
Project Purpose Maximize the Mississippi River connection to the Barataria. Terrebonne Basins to nourish and protect the marsh through the reintroduction of freshwater, sediments, and nutrients. Coastal Restoration Team
Phase 1 Summary • Developed 144 alternatives based on: – Route, Water Levels, and Dredge Cross Sections • Developed Screening Tools: – Phase 1 Model, Water Level Analysis, Cost Estimates • Developed Screening Criteria: – Minimum flow of 1000 cfs – Modify RR crossing in Donaldsonville – Water level rise below Donaldsonville is limited to 1. 5 ft above existing water levels – Water level wise below the weir in Thibodaux limited to 3 feet above existing water levels – Cost effectiveness of dredging • Screened alternatives using qualitative and quantitative criteria to a list of 7 final Coastal Restoration Team
Final 7 Alternatives Coastal Restoration Team
Phase 2 • Further development of Tabs/RMA model • WVA benefits • Refined cost estimates • Ranked alternatives Coastal Restoration Team
Phase 1 Model • • • An interesting thing happened along the way to developing a “quick and rough” model… The mesh for this project is the largest and most complex ever developed More representative of system topography, hydrology & hydraulics; Coastal Restoration Team
Finite Element Grid Coastal Restoration Team
Summary of Quantitative Values TABLE 4 -7 SUMMARY OF QUANTITATIVE VALUES AAHUs Cost/cfs ($) Cost/AAHUs/cfs Water Level Impacts ($) 170, 000 NA 166, 000 NA NA 4, 687, 000 1, 020 261, 000 1, 819 256, 000 143, 500 1. 78 4, 674, 000 32 1, 530 331, 000 2, 266 216, 000 146, 100 1. 48 4, 674, 000 38 970 184, 000 2, 031 190, 000 90, 600 2. 09 4, 674, 000 44 1, 400 251, 000 2, 164 179, 000 116, 000 1. 55 4, 086, 000 47 2, 000 379, 000 2, 203 190, 000 172, 000 1. 10 4, 086, 000 Least Rise 1, 000 379, 000 NA NA 1, 164, 000 Alternative Flow (cfs) Cost($) 15 1, 025 20 Coastal Restoration Team
Summary of Quantitative Rankings TABLE 4 -8 SUMMARY OF QUANTITATIVE RANKINGS Alternative Flow (cfs) Cost AAHUs Cost/cfs Cost/AAHUs/cfs Water Level Impacts 15 1, 025 1 NA NA 4 20 1, 020 4 5 5 3 2 3 32 1, 530 5 1 4 4 4 3 38 970 2 4 3 1 1 3 44 1, 400 3 3 2 2 3 2 47 2, 000 6 2 3 5 5 2 Least Rise 1, 000 7 NA 6 NA NA 1 Coastal Restoration Team
Summary of Qualitative Rankings TABLE 4 -9 SUMMARY OF QUALITATIVE SCORING Alternative 15 20 32 38 44 47 Least Rise Maintenance 5 4 3 5 3 2 2 Construction Impacts 5 3 2 4 4 2 1 Dredge Volume 5 4 3 5 4 2 1 Expandability 2 3 3 3 5 5 3 Stormwater Control. Flood Control 2 3 4 2 3 5 5 Diversion Flow 3 3 4 5 3 Permitting. ROWEnviron mental Impacts 5 3 2 4 3 1 1 Total Score 27 23 21 26 26 22 16 Criteria Coastal Restoration Team
Preferred Alternative Based on the remaining alternatives and the associated quantitative and qualitative criteria rankings, alternative #38 stands out as the best performing, most efficient alternative. Design refinement will be undertaken during the next phase to optimize this alternative. Reducing project cost will be emphasized during this phase. Coastal Restoration Team
Alt #38 Thibodaux Lockport Donaldsonville Existing ALT #38: BL, 2’-0’ RM 29, 1000 cfs, $183 M Coastal Restoration Team
Next Steps: Phase 3 SOW • • • Drainage Analysis Operation and Maintenance Plan Dredge Placement/Marsh Creation Geotechnical Investigation of Bayou banks Bridge Replacement/Reinforcement 95% Pump station design 95% Control structures design 95% Channel design Final EIS Final Plans and Specifications Final Cost Estimate Permits Coastal Restoration Team
Where are we now? Final Design (24 Months) Phase 2 Report March 2006 Final Phase 1 Report November 2005 Draft Ph 1 Report August 2004 Ph 1 Model Report And Water Level Analysis Funding ? June/July 2005 Historical Water Level Analysis May 2004 Review of Existing Data June 2003 Coastal Restoration Team
www. bayoulafourche. org Coastal Restoration Team
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