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Living on Sponge Cake May 23, 2008

Posted by The Typist in NOLA, Toulouse Street.
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Is anyone surprised that the U.S. Army Corps of Engineers, who thought it might be OK to stuff expansion joints in flood walls with newspaper in lieu of water proof seals, might have gotten it wrong in rebuilding and reinforcing the 17th Street Canal levees and flood walls, one of the major failure points of the 2005 Federal Flood? Perhaps they should try Bounty. Remember it was the Quicker Picker Upper because it was More Absorbent.

Among other things, [the Corps] repaired the wall by driving interlocking sheets of steel 60 feet into the ground, compared with about 17 feet before the storm. The sheet metal is supposed to prevent canal water from seeping under the levee through the wet, toothpaste-like soil that lies beneath the city, which was built on reclaimed swamp and filled-in marsh.

Over the past few months, however, the corps found evidence that canal water is seeping through the joints in the sheet metal and then rising to the surface on the other side of the levee, forming puddles and other wet spots.

Engineers said the boggy ground is a more serious problem than the corps realizes. [ob Bea, a civil engineer at the University of California at Berkeley,] said there is a roughly 40 percent chance of the 17th Street Canal levee collapsing if water rises higher than 6 feet above sea level. During Katrina, the water reached 7 feet in the canal.

Well, you would think that the events precipitating the Federal Flood would have led to some new thinking about how to build levees and other structures on our slippery, layered sponge cake soil, but the West Coast engineers think not. Just drive the piles deeper and hope for the best, which strikes me as an eminently 19th century solution.

It’s not as if this is a unique problem, or even a local one. I was surprised to learn while living in Fargo, N.D. that most large buildings required piles because of the characteristics of the bed of pre-historic Lake Agassiz–which in some age with a fancy scientific name rivaled the Great Lakes in size–upon which Fargo was built. I ended up helping my son research a short science essay on the subject and found the analogy to New Orleans fascinating. I sometimes think about the soils of Fargo and those 40+ foot dikes that keep the Red River of the North from drowning the place every spring.

Here’s an interesting tale from long ago about the building of a railroad embankment I used to drive along the route of (on Highway 10, a far-north, east-west analog of Highway 90 complete with parallel railroad tracks). Nothing under the sun, it seems, is new; and yet we seem to have such a confounded time figuring out how to deal with it all.

(Tim and Maitri, be sure to click the link. It’s definitely up your alley).

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