Surprise: "It's Not Their Fault"
So, it's not their fault. The interim government report on the 17th Street levee failure finds that was not caused by failings by the Corps of Engineers. Instead, it was the result of "A unique combination of stresses that engineers could not have predicted" and "a mechanism that we didn't envision" according to Walter Baumy, the deputy director of the Corps task force rebuilding the levee system.
"I would say it's certainly going to come as a surprise to many people, if not most people," said Ed Link, University of Maryland professor and task force project director.
Well it's certainly a surprise to me! And what exactly is this unforeseen mechanism that doomed the 17th Street canal? According to the
Times Picayune story the report states:
"-- As water in the canal rose to 10 feet -- an
unprecedented but not unplanned height -- the pressure from
the water and wind-driven waves in the canal began to push, or
deflect, the concrete floodwall and its subsurface supporting
steel sheet piling away from the canal and toward
Lakeview.
"-- The deflection created space between the wall and
the levee on the canal side.
"-- Such flexing is expected by designers, as is a small
opening between the wall and the levee. But what happened in
this case, and was not expected, was the separation extended
the entire length of the sheetpile wall to 17.5 feet below sea
level. Water rushed into this opening quickly, creating a
channel separating the floodwall from the levee on the inside
of the canal and allowing high water pressure to travel
directly down to the soil layers beneath the wall.
"-- The final blow came when a layer of clay about 15
feet below sea level that extended beyond the toe of the levee
began slipping toward Lakeview, causing the levee to collapse
and the wall with it."
The levee was built on weak soil. The floodwall was not built to
the level of the bottom of the canal as is common engineering
practice. The floodwall tilted back from the pressure because it
wasn't deep enough & was not properly supported. The water
rushing in the opening washed out the clay behind the levee. The floodwall failed, inundating the city.
And it wasn't their fault.
Hurricane season starts in less than 3 months. I am so comforted
by this report.
posted by Carl at 5:49 PM
2 Comments:
It might have been their fault for not thinking far enough ahead but it was not their fault that people were dumb enough to build their houses at ground level, when ground level was below sea level.
I never cease to be amazed at how many people like to blame other people for their own stupidity.
Anybody with brains should realize that you don't build a building below sea level no matter how strong you think a dam or levee are. Mother nature is very good at exploiting engineering weakness's.
You'll find no argument from me defending slab-built houses in New Orleans. We should, indeed, be building with an eye toward our environment.
But this in no way exonerates the Corps. They were given the task of building levees to resist flooding up to their tops. The water did not top the 17th Street Canal levee, but the city flooded anyway.
The Corps is responsible for the flood. Not the people whose houses were washed away.
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