June 22, 2105
By: Jacob Batte, HoumaToday.com
Dredging began today on a $16 million project to increase Mississippi River water flow into Bayou Lafourche.
That influx of fresh water will enhance the water quality to the bayou, which serves as the main source of drinking water for more than 300,000 people in Lafourche, Terrebonne and Assumption parishes.
It would also assist in the removal of invasive aquatic plants like hydrilla and taro, which trap sediment and create mud flats that block flow.
“The good part about having good clean fresh water is that it’s not just good for humans, it’s good for the wildlife,” said Susan Testroet-Bergeron, director of the Barataria-Terrebonne National Estuary Program. “We know that this is going to be great for everybody who uses the water.”
The second dredging phase of the massive Mississippi River Reintroduction to Bayou Lafourche project involves removing vegetation and dredging sediment and mud flats for 8.3 miles between Belle Rose and Napoleonville. Nearly 800,000 cubic yards of mud will be dredged.
In 2011, the Bayou Lafourche Fresh Water District completed a dredging project that opened nearly 6 miles of Bayou Lafourche between Donaldsonville and Belle Rose. This new phase picks up where the first left off.
In the miles just north of the Spur 70 bridge, vegetation creeps in from both banks, constricting the bayou and leaving just enough room for a large fishing boat.
Water elevation around Bell Rose sits at an average of 8 feet but would drop a more than half a foot after dredging, Freshwater District Executive Director Ben Malbrough said.
Following this project, Malbrough said the district will begin pursuing money to continue dredging to Thibodaux.
The Mississippi River Reintroduction to Bayou Lafourche project also includes bridge modifications, new water-control structures, replacement of the Union Pacific Railroad Bridge and the removal of the weir, or small dam, in Thibodaux.
When completed, Malbrough said the freshwater flow should increase from 330 cubic feet per second to more than 1,000.
“By increasing flow and depth of the bayou we’re probably going to be increasing the diversity as well as numbers of fish that are in the bayou,” said Andrew Barron, the Estuary Program’s water quality coordinator. “We would like to at least manage that submerged aquatic vegetation and the vegetation along the bank to keep it from really rebounding any time soon.”
Money for the project comes from the Coastal Impact Assistance Program, which sends revenue from offshore oil and gas production back to the state for coastal restoration projects. The district was awarded $20 million to use on the project with the stipulation that it must be completed by December 2016.
The remaining $4 million is being used to build a saltwater-control structure near Company Canal in Gheens. That structure, expected to be in place late next year, could be closed to halt saltwater intrusion into the bayou and act as a small dam in case a pump station malfunctions.
Malbrough said the weir to be removed in Thibodaux is a “huge operational nuisance.” If a tree falls in the bayou near Canal Boulevard, he said, the next closest launch that workers have access to is in Lockport.
Money has been set aside to analyze removal of the weir, installed in the 1960s to create a reservoir north of Thibodaux, Malbrough said.
“It doesn’t really serve any purpose anymore if we’re able to get enough water in the bayou,” Malbrough said. “The problem is our two biggest customers are Lafourche and Terrebonne, but their intake facilities are south of the weir. They would be the first two cut out.”
That project would result in about a 1.5 to 2 foot water elevation increase just south of the weir.
Bayou Lafourche was once a free-flowing tributary of the Mississippi, receiving 10 to 20 percent of the river’s flow. In 1904, the bayou was dammed at Donaldsonville to control flooding. A pump station was added in the 1940s to reintroduce freshwater and satisfy drinking water demand.
Bayou Lafourche’s health has suffered with diminished flow from the river. Sediment has filled in the waterway near Donaldsonville, threatening that area with flooding and lowering the water quality.
The bayou’s ill health became obvious during 2008’s Hurricane Gustav when fallen trees and storm debris clogged the bayou and turned the water stagnant, causing an unpleasant odor and making it unsafe to drink for weeks.