MELISSA BLOCK, host:
From NPR News, this is ALL THINGS CONSIDERED. I'm Melissa Block.
Today a government panel that's investigating why levees in New Orleans failed after hurricane Katrina issued some preliminary findings. The report is 800 pages long and it suggests that the U.S. Army Corps of Engineers, which oversees the levees, is not to blame. That's at odds with conclusions reached by two other independent teams.
NPR's David Kestenbaum reports.
DAVID KESTENBAUM reporting:
The government investigation is only partly complete, but it has now looked in detail at one dramatic failure, the breach of a wall that held back water in the 17th Street canal. It took days of dropping sandbags to plug the gap. But why did the wall fail?
Two teams of engineers, one funded by the state of Louisiana and one based at the University of California, Berkley, have previously put the blame on the Army Corps of Engineers and on a weak layer of ground below the canal walls. They said the design did not take that weak layer into account.
But the official investigation into the disaster says that's not right. It says the failure was something completely unforeseen. David Daniel is president of the University of Texas at Dallas and has been charged with providing an independent review of the official investigation. He says to understand what happened, imagine the canal wall.
Mr. DAVID DANIEL (President, University of Texas, Dallas): 17th Street canal consists of an earthen levee, which is just a long embankment of earth, that has a wall sticking up right in the middle of it.
KESTENBAUM: During the storm, the water level in the canal rose and at some point, the report says, the wall actually moved. It tilted outward, maybe just a few inches. But that, it says, opened up a gap with the earthen base and the water rushed down into the gap. Now, the water was pressing against the entire face of the wall. The wall might have held if it weren't for something else.
The report says that underground, just outside the canal in people's backyards, there lurked a weak layer of clay.
Mr. DANIEL: Once the movement started and the water pressures developed, there was enough force then just to cause an entire block to slide tens of feet and to breach the levee.
KESTENBAUM: The investigators say this conclusion is based on extensive computer models, soil samples, and even a miniature model of a canal wall that they tested by spinning it around in a centrifuge to mimic the forces of the event. David Daniel says the findings are a complete surprise to him.
Mr. DANIEL: It seems like a simple mechanism and it seems sort of intuitive now, but I can tell you as a professor who's taught courses in these areas, it was not something I've included in the courses I've taught.
KESTENBAUM: The report is likely to be welcome news for the U.S. Army Corps of Engineers, because it suggests the failure was not due to a simple design flaw. Ed Lank is a professor at the University of Maryland, and is leading the investigation.
Mr. ED LANK (University of Maryland): The classical design performed the way it was designed, except this particular failure mechanism was not considered.
KESTENBAUM: Lank says he doesn't know of any other wall that has ever failed this way. So is this anyone's fault?
Mr. LANK: I don't know. My job isn't to assess blame. I think everything we're doing is, we're attempting to focus on providing better protection, providing the knowledge for better protection.
KESTENBAUM: The report is likely to carry a lot of weight with the engineering community. The investigation is a big one. It involves the U.S. Army Corps of Engineers and many outside experts. Total cost is some $20 million. To ensure things are being done right, a team from the American Society of Civil Engineers is looking over the work and the National Academy of Sciences will also review things.
Billy Pruhoska, however, feels the report doesn't exonerate the Corps of Engineers. He's a geotechnical engineer and part of the investigation team being funded by the state of Louisiana. He says if the wall tilted outward, that proves there was a problem.
Mr. BILLY PRUHOSKA (Engineer): Well, if I design that wall and it failed like this one did, and you had that many people killed, I could go to jail for negligent homicide, more than likely.
KESTENBAUM: As a practical matter, the people of New Orleans will probably not have to worry about this kind of failure again. The Army Corps of Engineers is now building in gates, so that the canals can be sealed off from Lake Ponchartrain to the north of the town in case another hurricane comes.
David Kestenbaum, NPR News.
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