Sinking Sections of New Orleans Levee Prompt Repair

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The Army Corps of Engineers is spending $1.3 million to raise about 4,000 feet of earthen levee in easternmost New Orleans that has subsided so low it wouldn’t be able to withstand a storm surge caused by a so-called 100-year hurricane.

Corps Senior Project Manager Chris Gilmore tells The Times-Picayune included in the reconstruction is a 1,500-foot-long section on either side of U.S. 11 on the edge of the Bayou Sauvage National Wildlife Refuge and smaller areas between U.S. 11 and Interstate 10, and one small area just north of U.S. 90 in the same area.

The corps expected this area to settle significantly in a relatively short amount of time, and Gilmore said and “surveys of the reach (will) be taken annually for the first few years.” The repair will raise the levee for at least five to 10 years, he said. After that, he said, “a lift may be required to maintain the 100-year elevation.” The levee was actually “overbuilt,” raised to between 18 1/2 and 19 feet, or 1 1/2 to 2 feet above the 100-year level, and is being raised to that level again.

The biggest area of sinking occurred where rapidly subsiding soils were expected because they lie on top of an ancient slough, or depression, that was once a stream or river bed. The corps had installed a large field of wick drains that were designed to speed the removal of water from the soils. The drains were not affected by the rapid sinking, Gilmore said.

A nearby segment of levee over which a portion of the eastbound and westbound lanes of I-10 were rebuilt did not sink, he said.

The work is being done by a crew hired by the corps. The repairs were delayed for several weeks because high water in the Mississippi River limited the use of fill mined from the Bonnet Carre Spillway, which was partially flooded by water leaking through the spillway structure.