Preliminary plans for one of the future enhancements to the Morganza to the Gulf Levee system - the Grand Bayou Floodgate Structure - were unveiled at the South Lafourche Levee District’s January 9 public meeting in Galliano.
The floodgate, designed to hold back rising waters during a hurricane event and costing $21.9 million, will cross Grand Bayou in the Larose/Cut Off area just west of Apache Farm, also known as Paul Dufrene Farm.
CB&I, an engineering and design firm from Houma, offered three ideas for the gate on Monday, recommending a 134-ft. barge gate similar in operation to pontoon bridges.
Although Grand Bayou in that area is primarily a recreational-use waterway, the 134-ft. opening would improve water flow while allowing marsh accessible vessels to pass through its gate.
“The sizing of the structure will allow more fresh water to go to the Terrebonne/Lafourche estuaries, something that’s been requested for years,” said SLLD General Manager Windell Curole.
CB&I design engineer Mike D’Angelo outlined the plan for the barge gate, a 146-ft. long by 40-ft. wide by 30-ft. high structure which he said is the same type structure used in other similar projects in Terrebonne Parish.
This structure was chosen over two other designs for its ease of operation and maintenance, said D’Angelo.
One of the other two design ideas was a similar but narrower structure with sluice gates at a cost of around $21.5 million. It was not chosen because maintenance costs of the sluice gates would offset any upfront savings to the project, said D’Angelo.
The final design idea, a system of double-leaf sector gates with only a 50-ft. opening was about twice the cost to construct (about $40 million) and clearly not feasible, said Curole.
The floodgate idea is part of the project within Morganza to the Gulf known as “Reaches K and L”.
Reach K, a short levee heading north from Pointe-aux-Chenes, is now in construction phase.
Reach L is a longer levee along the west side of Grand Bayou heading north to the sight of the proposed Grand Bayou floodgate, then east toward Dufrene Farms.
Curole said it is important to note that the Terrebonne, Pointe-Aux-Chenes, and SLLD levee “ridges” are the only land bridges between Terrebonne and North Lafourche.
Until the Morganza projects are completed along Grand Bayou and tied into SLLD’s levee system, both parishes are subject to continued flooding from water entering the giant “hole” in the system at Grand Bayou.
Most of the Morganza project in Lafourche is in the design phase, with only some remaining money from Hurricane Gustav recovery funds (approximately $12 million) available for things like construction of Reach K and the planning of Reach L.
Lafourche’s benefit, said Curole, is in the fact that Terrebonne Parish and North Lafourche will be protected from flooding after the completion of Morganza to the Gulf.
Terrebonne Levee and Conservation District has taken the lead in seeking funding for the project from Louisiana State Capital Outlay as well as from donations from public and private sources, said Curole.
More information on “Morganza to the Gulf” can be obtained at www.tlcd.org
Posted on Fri, January 13, 2017
by By Buster Avera Contributing Writer