The Louisiana Coastal Wetlands Conservation and Restoration Task Force votes to close the West Bay Sediment Diversion
NEW ORLEANS – The Louisiana Coastal Wetlands Conservation and Restoration Task Force approved nine projects for design or construction and decided to close the West Bay Sediment Diversion in lower Plaquemines Parish during its quarterly public meeting this week in New Orleans.
The funded projects, which are spread across seven coastal parishes including Plaquemines, Jefferson, St. Charles, Lafourche, Terrebonne, Vermilion and Cameron, represent a commitment of more than $230 million in federal and state funds over twenty years.
Projects approved for construction:
• Cameron-Creole Freshwater Introduction, Vegetative Plantings - restore 200 acres of hurricane-impacted marsh in Cameron Parish at a cost of $1,147,096. The restored marsh will stabilize the area that will benefit from a freshwater introduction component of the project.
• BaratariaBasinLandbridge - protect three miles of shoreline along Bayou Perot and Little Lake in Jefferson Parish which is experiencing up to 15 feet of erosion per year. The project will protect 107 acres of marsh over twenty years at a total cost of $20,489,664.
• WestBelle PassBarrier Headland Restoration - restore the barrier headland function of this area that will provide a first line of defense for Port Fourchon, as well as Lafourche and Terrebonne parishes. The project will benefit 305 acres over twenty years at a total cost of $42,250,417.
• South Grand Chenier Hydrologic Restoration - introduce freshwater, sediment, and nutrients into newly created marsh in Cameron Parish, reducing salinities and increasing vegetative coverage. This project will benefit 352 acres over twenty years at a total cost of $29,046,128.
• GIWW Bank Restoration of Critical Areas in Terrebonne - restore critical lengths of deteriorated banks of the Gulf Intracoastal Waterway, reducing risk to the largest floating marsh complex in coastal Louisiana. This project will benefit 65 acres over twenty years at a total cost of $13,022,246.
Projects approved for design:
• Lost Lake Marsh Creation and Hydrologic Restoration - if constructed, would restore 749 acres of marsh along the shorelines of Bayou Decade and Lake Pagie in Terrebonne Parish at a total implementation cost of $22,943,866 over twenty years. Several water control structures would also be replaced to allow more freshwater and sediment input into the project area.
• Freshwater Bayou Marsh Creation - if constructed, would restore 279 acres of marsh along the western shoreline of Freshwater Bayou in Vermilion Parish at a total implementation cost of $25,523,755.
• LaBranche East Marsh Creation - if constructed, would restore 715 acres of marsh along the I-10 hurricane evacuation corridor in St. Charles Parish using sediment from Lake Pontchartrain, at a total implementation cost of $32,323,291.
• CheniereRonquille Barrier IslandRestoration - if constructed, would restore 234 acres of barrier island habitat in Plaquemines Parish at a total implementation cost of $43,828,285. The project would restore the island's function as a first line of defense against hurricane storm surges over twenty years.
West Bay Sediment Diversion Project closure:
The task force directed the Corps of Engineers and the state of Louisiana to close the West Bay Sediment Diversion Project because the long-term costs to dredge the Pilottown anchorage area adjacent to the West Bay Sediment Diversion outweigh the benefits of the diversion.
The U.S. Army Corps of Engineers, in partnership with the state of Louisiana, completed construction of the West Bay Diversion, located on the west bank of the Mississippi River above Head of Passes, in 2003 at a cost of $3.1 million. The project diverts the Mississippi River water and sediments into West Bay and has conveyed approximately 27,000 cubic feet per second of water into shallow water areas west of the river.
As part of the original project agreement signed in 2002, both the Corps and the state of Louisiana agreed that the Coastal Wetlands, Planning, Protection and Restoration program would pay to dredge a portion of the Pilottown anchorage area to offset anticipated project-induced shoaling. The Corps is not authorized nor funded to do so.
Since 2003, approximately 553 acres of fresh to intermediate marsh have been constructed by beneficially using the dredged material of the Pilottown anchorage area in the river. However, increased dredging cost have required substantially more funding than originally anticipated.
In addition, the diversion of water and sediment into West Bay over the last six years has not yet resulted in marsh creation. This can be attributed to many factors, such as the depth of water in the receiving bay, tidal storm surge, subsidence, incoming sediment grain size, or water velocities entering the area from the river.
As a result of much controversy over the cause of shoaling in the Pilottown anchorage area, the task force directed the Corps of Engineers to conduct an analysis of the West Bay Diversion project to re-evaluate shoaling impacts in the Mississippi River and the project’s performance in building land. The Corps has been conducting the most comprehensive data collection and modeling effort in the history of the Mississippi River to get a better understanding of the river’s water and sediment flow dynamics. This analysis will be complete before closure of the project in 2010 during the next low water event on the Mississippi River.
Closing the West Bay sediment Diversion will not prevent future implementation of other proposed diversions along the Mississippi River but the lessons learned will greatly contribute to future efforts.
"This is adaptive management, making decisions based on science and the performance that's occurring on the ground, to assure the resources of the river are being used to their highest priority," said Col. Alvin Lee, chairman of the task force and commander of the corps' New Orleans District.