Adding soil to east bank levees before armoring could cost $40M-$50M, levee authority told

Raising New Orleans area east bank earthen hurricane levees by a foot or two before allowing theArmy Corps of Engineers to install a combination of geotextile mat and Bermuda grass sod asarmoring against erosion caused by overtopping will cost the east bank levee authority between $40 million and $50 million, authority members were told Thursday (Oct. 16).

A more detailed estimate will be presented to theSoutheast Louisiana Flood Protection Authority-East by its staff in November, executive director Robert Turner said, after additional meetings to discuss the costs and the extent of the levee raising with corps officials next week.

The additional soil is needed to assure that the levees will continue to be high enough through 2028 to block storm surges caused by a hurricane with a 1 percent chance of occurring in any year, often referred to as a 100-year storm.

Without the additional soil "lift," officials would have to rip out the millions of dollars of geotextile mat used to armor the levee in a few years, when portions of the levees sink beneath the one percent protection level and the levees would need to be raised. A failure to raise the levees when they sink could result in the system being decertified, which could result in residents and businesses in the area losing flood insurance, or seeing higher flood insurance rates.

Most of the work will be required in Jefferson Parish and New Orleans. Most of the levees in St. Bernard Parish are topped by T-walls that were built about 3 feet higher than the surge height expected today, and won't require height adjustments for another 40 to 50 years.

Turner said the East Jefferson Levee District would rely on money it has and will have in its levee improvement fund, and on money it would request from the state's capital outlay budget for the lifts on its levees. The authority approved a resolution later in the meeting to request $29.6 million be included in next year's state capital outlay budget for the lifts there.

The Orleans Levee District's budget will have to be amended to address the increased cost, but at first glance, existing taxes are high enough to pay for the costs, he said.

The authority acts as the board of both the levee districts.

The Southeast Louisiana Flood Protection Authority-West is considering similar levee lifts in advance of armoring installation. The corps says thearmoring of all earthen levees on both sides of the river will cost about $300 million.

Authority member Rick Luettich, a civil engineer and professor of marine science at the University of North Carolina, questioned whether existing estimates of how high the levees should be are adequate, given a recent study for the authority that indicated the corps' storm surge modeling was already outdated.

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Adding soil to east bank levees before armoring could cost $40M-$50M, levee authority told