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LA Demands Floodwall Corrosion Study

Friday, March 24, 2017

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Floodwalls built to protect Louisiana’s St. Bernard Parish after the devastation of Hurricane Katrina may be at risk of failing, and state officials are blaming the corrosion of steel piles that were left uncoated because of cost and time concerns.

St Bernard floodwall
Images: U.S. Army Corps of Engineers

The St. Bernard floodwall system, with 32-foot-high walls atop clay-soil levees, has been questioned by some state and local officials, in part because uncoated steel pilings were used in its construction.

The 32-foot-high floodwalls were built between 2009 and 2011 atop clay-soil levees to prevent the kind of destruction brought by a storm like Katrina. The system was designed to withstand a so-called 100-year storm, one that only has about a one in 100 chance of occurring any given year.

History of Concerns

The Times-Picayune reports that in February 2015, the Army Corps of Engineers decided to install a monitoring system because of a fear that sinking in the earthen levees could bend the 100-foot, H-shaped steel pilings underlying the wall panels.

At that time, the Corps said it wasn’t concerned about corrosion. The Corps’s Col. Richard Hansen told the paper, "We have no cause for concern that corrosion will impact the performance of the structure," Hansen said. "In construction of the floodwalls, (the) Corps opted to use piles thicker than what is required, which allows some corrosion to occur while still allowing the piles to perform as needed throughout the project's design life of 100 years."

St Bernard floodwall

The St. Bernard floodwall project involved the construction of approximately 23 miles of concrete wall.

But the walls began showing signs of leaning and sinking after a December 2015 inspection. The concrete panels, built atop clay-soil levees, were separating, in some cases by more than an inch at the top, subsequent inspections showed. Some adjacent panels showed variations of more than half an inch in height.

Now, state officials have demanded that the Corps bring in an independent team to assess the project before the state will designate the project as being complete. The state has expressed concerns that corrosion on the pilings could indeed cause structural weakness that could render the floodwalls ineffective against a 100-year storm.

Coal-Tar Epoxy Skipped

In its original design for the wall structure, the Corps called for a coal-tar epoxy coating on the steel pilings. But the contractors on the job reported that the epoxy could not be applied on-site, and having the pilings coated would have added substantially to the project’s timeline and cost.

“All three said that trying to put some kind of coating on the piles was going to have some tremendous impact on the schedule,” the Corps’s John Grieshaber told PaintSquare News at the time. “If they could eliminate the coatings, there would be substantial scheduling advantages.”

The Corps then reportedly exempted the project from the epoxy specification because of cost concerns. The Corps permitted the contractor to install the pilings with no coating, relying instead of an extra 1/8-inch layer of sacrificial steel on the surface of the pilings.

The decision led to debate among officials and local residents at the time, with officials from the Southeast Louisiana Flood Protection Authority East arguing that the design was “flawed” without coatings on the steel pilings.

Not Yet Complete

The Corps reportedly sent the state of Louisiana a notice last March that the contract was complete, but The Times-Picayune reports that state officials refused to certify the project as complete until the corrosion issue is investigated by an independent team.

The issue is now reportedly subject to a 90-day period to establish precisely what the independent reviewers will report on, then the investigation is expected to last up to three months.

St. Bernard Parish, just east of New Orleans, lies on the coast of the Gulf of Mexico and Lake Borgne. During Hurricane Katrina, in 2005, the entire parish was left underwater. The population of the parish went from more than 67,000 in 2000 to about 7,000 in November 2006. It is estimated to be about 45,000 now.

The St. Bernard floodwall project involved the construction of approximately 23 miles of concrete wall, according to the Army Corps of Engineers. It was part of a larger, five-parish project with a total cost of $14.45 billion.

   

Tagged categories: Coal tar epoxy; Corrosion; Corrosion protection; Epoxy; Infrastructure; North America; Quality Control; Steel; Steel pilings; U.S. Army Corps of Engineers

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