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Marsh Creation With the Dedicated Dredge Program

Marsh Creation With the Dedicated Dredge Program. Luke E. Le Bas, P.E. Louisiana Department of Natural Resources. Dedicated Dredging Program. Initiated fiscal year 97/98 100% State Only funding through Wetlands Conservation Fund ≈ $1,000,000 budget per fiscal year. Program Goals.

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Marsh Creation With the Dedicated Dredge Program

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  1. Marsh Creation With theDedicated Dredge Program Luke E. Le Bas, P.E. Louisiana Department of Natural Resources

  2. Dedicated Dredging Program • Initiated fiscal year 97/98 • 100% State Only funding through Wetlands Conservation Fund ≈ $1,000,000 budget per fiscal year

  3. Program Goals • Use a small, mobile dredge to rebuild and/or nourish coastal marshes adjacent to small inland waterways • Establish numerous potential dredge sites by working with local groups (CZMs) • Consistently build projects that provide environmental & ecological benefits, marsh infrastructure stability, and that are economically feasible

  4. Completed Projects • 2 areas constructed to date • Lake Salvador – St. Charles parish • Bayou Dupont – Jefferson parish

  5. Lake Salvador Sites • Located on north shore of Lake Salvador • Within Salvador Wildlife Management Area • Between Baie du Cabange and Lake Salvador • 25.8 acres of estimated marsh creation • Site 1: 12.6 acres • Site 2: 13.2 acres

  6. Objectives of Lake Salvador Site • Prevent Lake Salvador from breaching into Baie du Cabanage • Strategic location provides long term erosion protection to organic, intermediate marshes around perimeter of Baie du Cabanage • Allow DNR to evaluate feasibility of different types of dredges for marsh creation • Evaluations based on dredge portability, draft, pump discharge size & hours of operation

  7. Lake Salvador Features • 400’ X 400’ borrow area located 500’ offshore • Spoil placement to average height 6” above existing marsh elevation • 1 ft. average water depth before dredging • Estimated dredging quantity for bidding was 124,734 CY based on cut-to-fill ratio of 1.5:1

  8. Work Accomplished • Construction completed 6/15/99 at a final cost of $342,276.37 • Approximately 25.8 acres of marsh created • $13,300 per acre of marsh created - Dike construction approximately $7 per linear foot.

  9. Beginning construction of containment dike on Lake Salvador

  10. Pumped material near final design elevation

  11. Retaining dike with dredge material dewatered

  12. Vegetation growth beginning upon completion

  13. Bayou Dupont Sites • Site 1 is adjacent to the southern shoreline of the Pen • Approximately 3 miles south of Lafitte. • Sites 2 and 3 are located along Bayou Dupont • Approximately 2 miles southeast of The Pen. • Estimated marsh creation at all three sites was 58.1 acres • 28.8 acres at Site 1 • 18.4 acres at Site 2 • 10.9 acres at Site 3

  14. Bayou Dupont Objectives • Rebuild portion of Barataria Landbridge • Relax specifications for dredge in hopes of obtaining lower bid price • Only restriction was dredge discharge size limited to 12” to ensure a reduced pumping rate for material to dewater and consolidate

  15. Bayou Dupont Features • 200’ wide borrow areas located a minimum of 50’ from the shore • Spoil placement to average height of 6” above existing marsh elevation Area 1

  16. Bayou Dupont Features (cont.) • Average water depths before dredging • 2.0 ft. at Site 1 • 1.5 ft. at Site 2 • 2.5 ft. at Site 3 • Estimated dredging quantity for bidding was 413,090 CY based on 1.5:1 cut-to-fill ratio Area 2

  17. Work Accomplished • Final estimated marsh creation: 160 acres • 65 acres at Site 1 • 95 acres at Sites 2 & 3 • Actual construction costs per acre totaled $6,800

  18. Dredge discharge in progress

  19. Pumped material near final design elevation

  20. Containment dike preventing effluent discharge from flowing into the Pen

  21. Existing marsh providing containment

  22. Fill site dewatered and planted. Fence surrounding vegetation is for Nutria deterrence.

  23. Project area fully vegetated

  24. Criteria for Selecting Future Sites • Shallow water areas approximately ±30 acres, with a maximum depth of water ≤ 2.5’ during high tides • Structural integrity of existing marsh enhanced and/or promoted • Existing containment in project area - Spoil banks or existing broken marsh • Minimum number of landowners (preferably one) • Minimal Oyster Lease impacts • Preferably no structures in Borrow or Fill areas • Proximity of Borrow to Fill area within 3 to 5 miles or less • Minimal amount of containment dike construction required

  25. The Future • To establish a prioritized list of proposed projects through coordination with the respective Coastal Zone Management boards • Permit and Design enough Small Dredge Projects so that an economy of scale can be realizedfor construction

  26. Questions • Prioritization process? • Permitting? • Construction?

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