Saltwater control structure to be built in Bayou Lafourche

By:  Meredith Burns,

August 27, 2015


Lafourche Parish officials hope to see construction on a new saltwater control structure along Bayou Lafourche completed next summer.

The roughly $3.4 million construction contract with Cayo LLC out of Fort Worth, Texas was awarded at Tuesday’s Parish Council meeting.

The structure, which will be located behind Linda Street in Lockport, is designed to block saltwater from creeping up Bayou Lafourche where it threatens local drinking water supply.

“It’s a pretty big deal for us. It’s going to be a big deal for the water district too,” said Lafourche Parish Administrator Archie Chaisson.

Saltwater-control structures work like floodgates, but instead of blocking flood waters, they’re closed temporarily when a canal or bayou is found to be carrying water with too much salinity. The structures are used throughout Terrebonne and Lafourche to help control saltwater intrusion from the Gulf of Mexico and keep it from destroying interior freshwater swamps and marshes.

Construction involves building new receiving walls in Bayou Lafourche north of the bayou’s intersection with Company Canal.

The steel barge will be taken from the existing Company Canal Saltwater Control Structure, retrofitted slightly and installed at the new structure in Bayou Lafourche.

“This is going to stop the water from creeping up the Company Canal and going north, but it’s also going to stop the bayou water from coming north,” Chaisson said.

The existing receiving walls will remain in Company Canal, Chaisson said.

“A large amount saltwater isn’t going to try to come up into the lake anymore because the channel will still be pretty choked down,” he said. “But again the freshwater is still going to be able to migrate south.”

Freshwater District Executive Director Ben Malbrough said the new saltwater control structure can be also be closed to form a reservoir in Bayou Lafourche north of the gate, which will allow the freshwater district to remove the existing weir in Thibodaux.

While the weir works great for some communities, Terrebonne and Lafourche intakes are south of the weir and do not see any benefits, he said.

“If something were to happen where the pump station up in Donaldsonville was shut down for an extended period of time, the first two customers that are left out of the system are Terrebonne and Lafourche,” he said. “With this structure being put into place, it will be able to act as a weir and create a reservoir for all the water plants along Bayou Lafourche, not just Thibodaux, Assumption and Ascension.”

The weir in Thibodaux is also an “operational nightmare” for the freshwater district.

“If a tree were to fall just south of Canal Street Bridge today, we have to drive all the way down to Lockport to launch a boat and drive all the way up Bayou Lafourche from Lockport to do any work in an incident like that,” he said.

Officials are looking forward to moving forward with a project that has been on the books for about a decade.

Earlier this year, state Coastal Protection and Restoration Authority officials said the project would be postponed again because surplus dollars set aside for the project would not be available in anticipation of state budget cuts.

Malbrough said the CPRA staff and board have since been instrumental in directing construction money to the project through the Coastal Impact Assistance Program grant.

The grant requires money to be spent on the saltwater control structure by the end of next year.

“The estimate is it will be sometime next summer, but come hell or high water that thing has to be done by Dec. 31, 2016 or we could potentially lose funding for it,” he said.

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