Corps: Foundation Problem in Levees Blamed
By JANET McCONNAUGHEY, Associated Press Writer
1 hour, 12 minutes ago
NEW ORLEANS - A foundation problem — although not the one targeted by
earlier studies — caused the 450-foot-long break in a floodwall and
levee on New Orleans' western edge when Hurricane Katrina hit, the
U.S. Army Corps of Engineers said Friday.
A naturally occurring, 20-foot-thick layer of clay that helped support
the floodwall was too weak for the job, according to a report by a
Corps task force set up to find out why the levees broke. Had the
floodwall and levee held, much of the western half of the city would
have escaped flooding.
Previous analyses by other groups had targeted the layer of sand and
peat over the clay as a likely culprit.
"The failure plane was not in the peat. It was in the clay below the
peat. That became the weakest part of the system," said Ed Link,
project director for the study by the Interagency Performance
Evaluation Task Force.
Part of the levee was pushed 40 feet backward, and can be seen above
the water — along with that section of floodwall — in an aerial
photograph published as part of the task force's second report.
High water pushed back the floodwall, which is set into the center of
the earthen levee. Once water got between the floodwall and the front
half of the levee, it effectively cut the levee in half lengthwise.
The floods then pushed the floodwall, and the half of the levee behind
it, backward on a layer of soft clay below the surface, the report
said.
The floodwall's design didn't include either the possibility that
water could get between it and the levee or that the clay might be
unstable, corps officials and others said in a news conference. The
two factors combined created the breach, they said.
"We are incorporating the information into our current repairs, and
incorporating it into our assessments for the future," said Col. Lewis
Setliff, who is in charge of the levee repairs that the Corps wants
completed by the beginning of next hurricane season on June 1. "We are
also evaluating the repairs we are making ... to see if we need a
change of course."
Setliff said the corps is looking at all the "I-walls" — vertical
concrete barriers anchored by vertical sheet steel pile — in New
Orleans-area levees.
The 17th Street Canal and two others that broke during and after
Hurricane Katrina will be cut off at the mouth by new floodgates if a
hurricane approaches this year, to keep high water in Lake
Pontchartrain from stressing their levees and floodwalls.
And, wherever it can, the Corps is replacing I-walls with "T-walls,"
which have a horizontal concrete base and are anchored by steel beams
driven diagonally through the levee.
Those should be "significantly more resistant" to such failures Link
said in a news conference after the 332-page report and more than 400
pages of appendices were released Friday on the Internet.
The report released Friday is preliminary. The final report is due
June 1.
--
"The president and I cannot prevent certain politicians from losing
their memory, or their backbone, but we're not going to sit by and
let them rewrite history." -- ***** Cheney 11/16/2005
"War is God's way of teaching Americans geography" -- Ambrose Bierce
"America is a vast conspiracy to make you happy." -- John Updike
"Long term commitment in relationships is only necessary because it takes
so damn long to raise children. Marriage may well be some kind of trick
to keep the males around beyond sexual satiation." -- Captain Compassion
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--Will Durant
Joseph R. Darancette
daranc@NOSPAMverizon.net
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