• The Mississippi: A Visual Biography by Quinta Scott

    "Great book and great blog - thanks for the first book I have seen that addresses the contemporary river, headwaters to gulf." Dan McGuiness, Audubon, St. Paul, Minnesota

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Beneficial Use of Dredge Material

Len Bahr at lacostpost.com has an interesting post about the beneficial use of dredge material to rebuild 440 acres of marsh near Black Lake and 227 acres in the Sabine National Wildlife Refuge to the south, using material dredged from the Calcasieu Ship Channel.

Beneficial Use of Dredge Material:  such an awkward,  bureaucratic term; such a useful tool for wetland restoration.

In the 1992 Water Resources Development Act, Congress authorized the Corps of Engineers to turn sediments dredged from navigable waterways into something useful: wetland restoration.

Now Louisiana would be able to use sediments dredged from MRGO, the Houma Nav, the Barataria Waterway, the Calcasieu Ship Channel, and others to rebuild wetlands.

They already had. I think the first project was the reconstruction of Queen Bess Island in Barataria Bay with dredge scooped up from the Barataria Waterway. The project restored the island and saved a rookery for brown pelicans, the Louisiana state bird.

Louisianan moved on to other projects, where they used beneficial use of dredge material

Marsh restoration along Bayou Rigolettes

Marsh restoration along Bayou Rigolettes with dredge material

It took a century for Bayou Rigolettes and its twin Bayou Perot to enlarge from narrow bayous, running through the Barataria Landbridge, to elongated lakes with a diminishing ridge of marsh between them. The landbridge is the transition between salty Barataria Bay to the south and the freshwater marshes and forests to the north.

If you will remember, the Barataria Landbridge absorbed much of the punch of Hurricane Gustav’s storm surge.

In 2006 engineers began constructing a concrete sheetpile structure,  pre-cast, slabs of concrete, eight feet wide, twenty feet long, and six inches thick set vertically between sixty-foot long concrete piles having an H-configuration in the top twenty feet into which they slid the slabs.

Bayou Rigolettes Wall and Pelicans

Bayou Rigolettes Wall and Pelicans

The engineers chose the sheetpile structure because it would be less likely to sink in the soft, marshy soil. They set the slabs 3.5 feet above sea level.

Dredge pumped  behind containment wall.

Dredge pumped behind containment wall. The cranes in the background are used to set the posts and slide in the concrete slabs.

The marsh would continue to submerge, but more dredge could be pumped in later.

With the demand for sediment for building marshes and levees in Louisiana escalating, Len Bahr raises the question: Where is all this mud going to come from?

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2 Responses

  1. […] year folks working on restoring the Barataria Landbridge, deposited 1,800 acres of soil behind a concrete wall designed to keep the new soil from eroding. The marshes in the landbridge lies between Barataria […]

  2. Quinta,

    Forgot you had a blog about our coastal issues. Great work!

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