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Atchafalaya diversion project gets $16M boost

By ZACHARY FITZGERALD zfitzgerald@daily-review.com

A project to divert water from the Atchafalaya River to bring fresh water and restore land in Terrebonne Parish got a major boost Tuesday for its design phase.
The National Fish and Wildlife Foundation announced the award of five projects totaling over $245 million from its Gulf Environmental Benefit Fund to the Louisiana Coastal Protection and Restoration Authority, according to a Coastal Protection and Restoration Authority news release.
The projects are designed to advance critical river diversion projects in the state’s master plan for a sustainable coast, the release said.
A project to create a fresh-water diversion from the Atchafalaya River to protect marshes in upper Terrebonne Parish will receive about $16.4 million in funding to advance its engineering and design.
St. Mary may also benefit from the project by “keeping a vibrant system of marshes” between Morgan City and Terrebonne, thus lessening the impact of hurricanes, project manager Austin Feldbaum said.
Historically, hurricanes that have hit St. Mary Parish tend to come from the southeast and come up through Terrebonne Parish, Feldbaum said.
The Louisiana Coastal Master Plan identified this project as a way “to harness the Atchafalaya River to stem the dramatic erosion in this area of Louisiana’s fragile coast,” according to the CPRA website.
The funds will get the project through 30 percent design stage, which will probably take 1 1/2 to two years to achieve, Feldbaum said.
All major questions about the project’s scope and potential environmental effects will be answered by the end of 30 percent design, he said.
Once constructed, the diversion project will restore freshwater influence in this basin and reduce wetland loss by approximately 13,000 acres over 50 years, the CPRA website states.
“It’s being designed to be able to be operated for 50 years and beyond if we so choose,” Feldbaum said.
Terrebonne Parish’s wet-lands experience the highest rate of land loss in all of coastal Louisiana, the CPRA website states. Starved of freshwater, sediment, and nutrient supply that sustained them, Terrebonne’s wetlands are expected to lose in excess of 146,000 acres of wetlands by 2050 with no further restoration action.
Bringing fresh water east into the upper reaches of the Terrebonne marshes will help sustain and restore some of the most threatened areas of Louisiana’s fragile coast, the website says.
This project will begin the design and environmental review required to construct a river diversion, using fresh water and sediment from the Atchafalaya River and dredged material to build, sustain, and maintain wetlands in the Terrebonne Basin, the CPRA’s website says.
Port of Morgan City Economic Development Manager Cindy Cutrera said port officials have concerns about the diversion and are requesting to see modeling of the effects on the Atchafalaya River and Bayou Chene. Port officials want to see what effects the diversion will have on the velocity of the river along with the salinity and sediment accumulation in the river, Cutrera said.
“We’re all about helping Terrebonne,” Cutrera said. “When their coastline is healthy, then that protects us from hurricanes. But we don’t want to have problems for industry in the area by having issues in the waterways.”
Feldbaum said coastal protection officials have done studies to examine some of those concerns, particularly how the water will move through the diversion.
Therefore, researchers can infer a lot about what will happen to the sediment in the diversion, Feldbaum said. CPRA officials plan to do “a more complete study of sediment transport modeling,” he said.
Feldbaum doesn’t expect sediment buildup to be a major problem in this case due to the way officials intend to operate the diversion structures, he said.
The diversion consists of a series of large gates that officials can open and close to control water flow. Officials plan to close the gates when water levels are highest, and most of the sediment moves when the water is highest, he said.
As water is pulled from the Atchafalaya at the Intracoastal Waterway and some of the water is sent past the Bayou Boeuf locks, half or more of that water gets back to the Atchafalaya River south of Morgan City by going back down Bayou Boeuf or some other waterways, Feldbaum said.
Most of the dredging work that takes place is done south of that point, he said.
Coastal restoration officials will hold a public meeting at 10 a.m. Dec. 8 at the Port of Morgan City’s Government Emergency Operations Center to discuss the river diversion to Terrebonne Parish.

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