The U.S. Army Corps of Engineers built the New Orleans area levee system with appropriate guidelines and was generally justified when it sought waivers from those guidelines, according to a new report released Wednesday.
The Water Institute of the Gulf released the report, which had been requested by the state Coastal Protection and Restoration Authority, as the state and local entities continue to take over operation and maintenance of the system.
The Water Institute set up a six-member expert panel from around the country to evaluate the guidelines used to build the risk reduction system and four waivers to that design.
The waivers included resiliency design checks for the Inner Harbor Navigation Canal, steel pile corrosion protection, use of spiral welded pipe for foundations and deflections of proposed Inner Harbor Navigation Canal floodwall.
Generally, the waivers were appropriate and consistent with standard practices, said panel member Robert Gilbert, of the University of Texas.
However, he said, the waiver for adding additional steel to pilings used in a 23-mile section of floodwall in St. Bernard Parish wasn’t consistent with current practices.
Normally, the steel piles that support the floodwall underground would be coated with a substance to stop corrosion, Gilbert said. To save time, the Corps decided to increase the size of the pilings to account for any corrosion.
“It will now be the responsibility of the state to monitor these pilings,” Gilbert told the Coastal Protection and Restoration Authority at its Wednesday meeting.
Several members of the authority said the state tried to protest the measure but didn’t prevail. Now, they say, it’s the local sponsors who will need to maintain the structure.
Gilbert said although it means the section of floodwall will need to be monitored more closely, “this doesn’t mean the sky is falling or that the wall won’t work when a hurricane comes.”
Ken Holder, spokesman with the Corps office in New Orleans, said corrosion was an important design consideration in building the system and the Corps uses several different ways to control for corrosion, including coating the pilings or using more steel thickness.
“Different measures to inhibit corrosion were used for various projects within the system, depending on the project design, soil conditions, location and construction materials,” Holder said. Using additional steel thickness is an accepted engineering method to inhibit corrosion, and it’s quicker to use, which helped the Corps get to 100-year level of risk reduction before the start of the 2011 hurricane season, he said.
In St. Bernard, the Corps used more than 50,000 steel piles for the work. Using thicker steel instead of coating each pile saved a lot of time in order to meet the 2011 deadline, he said.
Other expert panel recommendations included making sure to communicate the continuing risk of hurricanes and flood surge to the public, periodically updating the risks associated with being behind the levee systems and better collaboration between the state and the Corps.
Follow Amy Wold on Twitter, @awold10.