Levee sheet pilings only driven about half as far

[sunny]

And here you go. wwltv.com


Tests confirm levee sheet pilings only driven about half as far as recommended

06:43 PM CST on Wednesday, November 30, 2005
Brett Martel / Associated Press

Government engineers performing sonar tests at the site of a major levee failure found exactly what independent investigators said they would -- that steel reinforcements barely went more than half as deep as they were supposed to, a U.S. Army Corps of Engineers official said Wednesday.

"We've come up with similar results" to those from earlier tests performed by a team of Louisiana State University engineers, said Walter Baumy, the Corps' chief engineer for the New Orleans District.

Baumy said the Corps now intends to pull out pieces of the remaining wall along each edge of the breach at the 17th Street Canal to verify the results of the sonar tests. The canal itself is now mostly dry at the site of the breach, with temporary walls holding back water from each side, allowing for excavation.

Baumy said the Corps remains unable to explain the disparity between what their 1993 design documents show was supposed to be there and what they've actually found.

The documents indicated that the steel reinforcements in the levee, known as sheet piling, went down to a depth of 17.5 feet below sea level. Sonar tests indicated the pilings went only to 10 feet below sea level, meaning the flood wall would have been much weaker than advertised.

The LSU team is working on a report for the state Department of Transportation -- due out in January -- that will say that there were serious, fundamental design and construction flaws at both the 17th Street and London Avenue canals. Both broke during Hurricane Katrina, allowing flood waters to pour into the city's western and central neighborhoods and encroach on downtown.

The team's leader, Ivor van Heerden, said Wednesday that the levee design ensured failure under the type of water pressure exerted by Katrina's storm surge.

The team's computer modeling showed that the designs failed to account for loose, porous soils such as sand and peat that were prone to allowing water to seep from the canal through to the dry side of the levee.

Much deeper steel pilings driven well below the canal bottoms likely would have stopped seepage to the dry side of the levees, engineers have said. But the bottom tip of the pilings, at 10 feet below sea level, did not even reach as deep as the canal bottoms.

"Now that we've done the soil strength calculations and looked at the actual design, the design wasn't up to the task," van Heerden said. "You have a section of canal that wasn't covered by sheet metal."

LSU computer models showed that even if the pilings had gone to 17.5 feet below sea level at 17th Street as design documents said they should have, they still would have failed.

Engineering studies prior to construction of the flood wall were performed by Eustis Engineering, Modjeski and Masters Inc. and the Corps. Members of van Heerden's team have expressed shock that all three could have missed what they characterized as fundamental flaws. Calls put in to Eustis and Modjeski and Masters were not returned Wednesday. However, van Heerden said the federal government bears ultimate responsibility.

"The federal government built the levees, the federal government supplied that security, the security system failed, as a consequence these 100,000 families have lost everything," van Heerden said. "In our opinion, the federal government needs to step up to the plate."

(Copyright 2005 by The Associated Press. All Rights Reserved.)