Whiskey Island Marsh Creation Rolling with the Punches Santiago Alfageme, M&N Jerry Carroll, LADNR Brad Miller, LADNR
Project Location
Historic Island Retreat
Previous Restoration Project Whiskey Island Habitat Areas (Nov 2002) East Flank (TE-27) Restoration Area
Project Sponsors Coastal Wetlands Planning, Protection and Restoration Act (CWPPRA) Federal Sponsor U.S. Environmental Protection Agency Local Sponsor Louisiana Department of Natural Resources
Project Goals To increase the longevity of previously restored and natural portions of Whiskey Island by increasing the Island s width to help retain sediment volume and elevation. Approximately 300 acres of back barrier, intertidal habitat Constructed tidal creek and pond features Dune feature to restore relatively low Gulf-side elevations Vegetate newly created marsh and dune areas
Design Team T. Baker Smith, Inc. (TBS): Lead project consultant Moffatt & Nichol (M&N): Coastal engineering, numerical modeling, and engineering design Ocean Surveys, Inc. (OSI): Geophysical data collection program and sediment mapping Eustis Engineering Company, Inc. (Eustis): Geotechnical engineering University of New Orleans, Department of Geology and Geophysics: Sediment Analysis Archeological Research, Inc.: Archeological resource investigation
Project Challenges 20-year project life without any maintenance Intertidal marsh over maximum period of time Very dynamic coastal environment Extreme erosion rates Complex physical processes (inlets, RSLR, storms, ) Mix of sandy and silty sediments Incorporating tidal creek and pond features
Back Barrier Marsh Design Dike lowered to +1.0 NAVD at creek Tidal Creeks & Ponds Dikes lowered to marsh elevation at demobilization Marsh Construction Elevation: +2.5 AVD88
Tidal Creek Section
Typical Primary Dike
Construction Quantities Construction Item Volume Area/Length Volume per Unit Area/Length Marsh Fill 2,300,000 cy 316 acres 7,300 cy/acre Primary Containment Dike (20 ft crest) Secondary Containment Dikes (10 ft crest) In-place Volume Requirements 92,000 cy 5,000 ft 18.4 cy/ft 75,000 cy 12,000 ft 6.3 cy/ft Tidal Creeks and Ponds 49,000 cy 5,800 ft 8.4 cy/ft Dune Fill 225,000 cy 13,000 ft 17.3 cy/ft Estimated Cut Volume Requirements from Borrow Area Construction Item Volume in Place Cut-to-fill Ratio Assumed Volume Required in Borrow Pit Marsh Fill 2,300,000 cy 1.2 2,760,000 cy Dune Fill 225,000 cy 1.6 360,000 cy
Numerical Modeling: Delft3D Morphological Bathymetry (ft MSL)
Sediment Distribution in Morphological Model Depths 0 to 2ft from bottom 80% Silt/Clay 20% Sand 95% Silt/Clay 5% Sand 2% Silt/Clay 98% Sand Background Mixed Sediment 60% Silt/Clay 40% Sand 80% Silt/Clay 20% Sand 2% Silt/Clay 98% Sand Depths 2 to 5ft from bottom
Habitat Area Projections for WVA Area Estimates at Target Years (acres) Habitat TY1 TY3 TY5 TY10 TY20 Dune 48 36 24 0 0 Supratidal 164 132 118 105 25 Gulf Intertidal 295 285 275 250 200 Bay Intertidal 550 559 539 489 389 Subtidal 1 1 1 1 1 TOTAL 1058 1013 957 845 615
Potential Borrow Sites
Excavation Layout 3,800,000 cy of Marsh Material 593,000 cy of Dune Material
Construction Timeline Bid opening - Dec 08 Low bidder: Weeks Marine $23M Construction Contract Jan 09 NTP Feb 09 Mobilization & Construction Start Mar 09 Completion & Acceptance Nov 09
Start of Marsh Fill: June 2009
Substantial Completion: October 2009
Aerial Photo: December 2009
April 2010 Monitoring Survey
April 2010 Monitoring Survey
Summary & Conclusions Project achieved initial restoration goals Optimization of available sediment resources Pre-excavated tidal creeks and ponds have settled below adjacent marsh areas More time needed before final assessment Marsh constructed above design and pay tolerance elevations
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