17th Street Canal Half Ful of Silt: Guest Post By Matt McBride

Aug 17, 2007 by

Dear New Orleanians and those who care about our city,
The 17th Street canal Safe Water Level report is the gift that keeps on giving. It is linked here:
On page 53 (Adobe page 54) is a passage called “Sedimentation.”
Here’s what it says:
(3) Sedimentation. The post Katrina surveys show that the accretion has occurred in the

canal. Between I-10 and the railroad bridge the lowest canal bottom elevation is El. -10

NAVD or over 7 ft. of sedimentation according to post Katrina surveys. Between

Veterans Blvd and I-10 the canal bottom elevation is El. -14 to -18 NAVD or between .5

to 3 feet of sedimentation according to post Katrina surveys. Between the B/L Station

583+00 and Veterans Blvd the canal bottom elevation is El. -15 NAVD or higher about 4

feet of sedimentation according to post Katrina surveys. Between Hammond Highway

Bridge and Station 583+00 the canal bottom is between El. -17.5 NAVD and El. -19.5

NAVD (at one location 120 ft south of Hammond the bottom elevation is -20.0 NAVD)

about .5 ft to 2.5 ft of sedimentation. Since the surveys were taken 18-inches of riprap

has been placed on the canal bottom from Hammond Highway to the south end of the

breach.

 
So the canal bottom, for nearly half its length (from I-10 to the railroad bridge, which is the southernmost part of the canal, right in front of Pumping Station 6) is nearly half full of silt.
It’s hard to imagine this isn’t having any impact whatsoever on drainage in this city. A canal that is significantly clogged with debris almost two years after the storm, and no one has noticed? The Corps has even added to the level of the canal bottom with another 18″ of riprap.
It’s a good bet the other two outfall canals and the Indistrial Canal also have tons of junk on their bottoms. Does this make water rise higher in the canals, making them less safe?
The City of New Orleans is still cleaning silt out of its drainage pipes under the streets, and expects to be doing so for another year, at least. So why isn’t anyone doing the same for the biggest parts of that drainage system – the canals?

Matt McBride

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