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Floodwall probe focuses on weak soil

Engineers are conducting the equivalent of a forensic investigation at the levees and floodwalls of New Orleans, drilling deep into the earth to examine the soil itself.
/ Source: NBC News

Engineers are conducting the equivalent of a forensic investigation at the levees and floodwalls of New Orleans, drilling deep into the earth to examine the soil itself. The Army Corps of Engineers is looking for evidence that could explain why the flood defense system the agency designed to protect the city was instead overwhelmed by Hurricane Katrina.

Already, one investigator who testified Wednesday before a Senate committee said there may have been "malfeasance" in the building of the levees, while a report blamed "failures in the foundation soils"  for the worst floodwall collapses.

Investigators want to know if Katrina's devastation in New Orleans was caused in part by fatal errors on the part of the agencies that designed and built the levee system, and for now, attention is turning to the Army Corps of Engineers itself.

Veteran soil expert Herbert Roussel worked as a consultant for the contractor hired by the Army Corps of Engineers to build the 17th street floodwall more than 10 years ago. "We noticed that the soil was weak," he said in an interview with NBC News, "and it was pointed out to the Corps of Engineers that we had weak soil there."

As NBC News first reported in September, that contractor, Pittman Construction, complained about the soil to the Army Corps of Engineers and filed a contract complaint. Pittman Construction's job was to pour a concrete wall atop a metal sheet that was already embedded along the canal, bolstered by earthen embankments. But the firm said the walls would shift.  Roussel, as part of the case in a 1997 document alleged there was a "latent defect relative to the construction phase of the project. This defect is due to a weak soil..."  However, he never raised safety concerns back then, just concerns about construction.

The floodwall at the 17th Street Canal, built  by Pittman Construction, was one of those that failed, as did the London Avenue Canal floodwall, which was built by other contractors. The walls failed even though the water did not reach all the way to the top. In other words, they did not do what they were supposed to. Now one focus of investigators is a layer of weak, spongy soil called "peat."

‘Did nothing!’
But Roussel says it all could have been prevented if the Corps had simply listened to the reports of its own contractor. "Why didn't they look at that and say, 'Maybe we have a problem. Let's see if we can fix it.' But the Corps of Engineers did nothing!"

Pittman Construction is now defunct but Roussel, in his files, has an Army Corps of Engineers document that shows a five-foot layer of peat under the ground. That proves they knew about the peat, he says.

That is important because the current theory about why the walls collapsed at the 17th Street Canal is that the layer of peat played a role, becoming soft and wet as the water rose during the hurricane. Since the entire floodwall structure topped a layer of peat, investigators now believe the floodwaters simply pushed the entire structure out of its way, sliding it into the city and allowing the water in.

Meanwhile, at Wednesday's hearing before the Senate Homeland Security and Governmental Affairs Committee, committee chair Sen. Susan Collins said that the failures of the levees, in part, "were the result of human error in the form of design and construction flaws."

Human error?
Professor Raymond Seed, who runs an investigative team funded by the National Science Foundation, said there may be wrongdoing as well as human error.

"There may have been malfeasance," he said. He said perhaps contractors had not driven metal sheets as deeply into the ground as they were supposed to, or had not constructed the levees according to the way they were designed.

Paul Mlakar of the Army Corps of Engineers, promised a thorough investigation. A spokesman for the Army Corps says the construction documents, including the complaints by Pittman, will be part of the probe.