With each passing day, it is becoming more evident that Hurricane Katrina did not flood New Orleans.
This is probably the most bizarre thing I’ve ever blogged. It is completely unfathomable how this happened. But it did.
WASHINGTON — When the Texas construction firm AquaTerra Contracting began work on an Army Corps of Engineers hurricane protection project on the West Bank, it encountered a serious problem: Its floodwalls wouldn’t stand up straight in the mushy soil.
AquaTerra workers tried driving steel sheet piling down to the 55-foot depth the design required for the walls’ foundation, company CEO Clay Zollars said. But the piling, driven along a new drainage canal near the Cousins Pump Station, began to lean inward.
Zollars said the corps went back to the drawing board and decided to better anchor the wall, nearly doubling the length of the steel foundation to 105 feet. That didn’t work either.
“Before we completed the wall, it began to lean and sink also,” Zollars said. “The pilings were inadequate. The corps corrected that by installing some additional reinforcing steel in the concrete, but the wall still is leaning.”
The top of one section of the 10-foot concrete wall is more than a foot off the vertical, he said. AquaTerra is seeking $5 million it says the corps owes it for the extra work on the $11.1 million contract. Corps officials won’t comment on the case because of the dispute.
A 10 foot floodwall more than a foot off vertical? That didn’t ring alarm bells that something was wrong? If you were having a house built and the top of the wall was a foot askew from the bottom of the wall, would you move in? If the contractor said he couldn’t do any better would you just accept it?
Before they could even finish the project the walls were both leaning AND sinking.
They drove the pilings down 105 feet and that didn’t work either. It should have been obvious to a third grader the design was fundamentally flawed.
‘A poor choice’
“They were struck with a bad situation, and they made a poor choice with those floodwalls, trying to put a structural wall on plastic soils. It’s like putting bricks on Jell-O. There isn’t a lot of support,” said J. David Rogers, a veteran forensic engineer who specializes in dam and floodwall failures.
What is unclear is how the corps and its contractors went forward with designs that some engineers now say appear fundamentally flawed. A team of engineers at the University of California at Berkeley studying the levee failures said that the corps’ design standards do not seem to have accounted for all the soil uncertainties, raising questions about the design of the entire levee system.
That’s the big question. Why the hell did the Corps of Engineers continue to use a design that was so obviously flawed?
The challenges of building floodwalls in weak, wet soils are well-known to engineers. A corps design manual warns that “by their very nature, floodwalls are usually built in a flood plain which may have poor foundation conditions.”
Unexpected problems with weak soil have cropped up before. The AquaTerra case resembles a 1990s dispute concerning the 17th Street Canal floodwall. Segments of that wall also tipped off-center when the concrete wall sections were poured, requiring additional work and sparking a legal tangle. As with AquaTerra, the corps left the leaning walls in place.
These walls can’t support their own weight and they were supposed to stand up to a hurricane?
Yes, this stuff is enormously complicated but at some point common sense has to tell you have a problem. You don’t need sophisticated computer models to tell you that if a floodwall can’t support it’s own weight it won’t hold back much water.
Engineers say that the corps standards required an unusually low safety factor for the floodwalls, perhaps a remnant of a time when most levees protected sparsely populated rural areas, not cities and suburbs. A higher safety factor would require stronger walls — and cost more.
The AquaTerra, 17th Street and London Avenue walls are all “I-wall” designs, the least expensive type of concrete floodwall, consisting of linked concrete sections built on a sheet pile foundation. Other types of walls have additional horizontal bracing, either at the base of the concrete sections or in piles extending diagonally into the earth.
The floodwalls that broke causing the most damaged where built less than 10 years ago which was about a half a century after billions of dollars of homes were built. Why did they still use an “unusually low safety factor?” Wouldn’t you think in the last half century or so the corps would have noticed a few hundred thousands homes being built?
But some of the most damaging evidence yet released was buried in this article.
It’s been obvious for about the last 100 years or so that the soil where the floodwalls were built was a problem. It should be noted that when presented with this problem in the form of leaning floodwalls, the Corps did NOT address the real problem (below ground) it added reinforcements to the concrete (above ground) to simply mask the problem. In engineering this is a big NO-NO. If the skin is peeling off an airplane wing you don’t darken the windows so the passengers won’t notice.
Katrina did not flood New Orleans. The U.S. Army Corps of Engineers did.
And on a personal note: Would all the arm chair engineers from last month who defended the Corps so vigorously and said I was just being emotional like to apologize now?