Dredging May Have Doomed New Orleans

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Dredging led to deep trouble, experts say
Levee 'blowout' was a concern before project began in 1980s

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When the New Orleans Sewerage & Water Board developed a plan in 1981 to improve street drainage by dredging the 17th Street Canal to increase capacity for Pump Station No. 6, residents across the city applauded. Increasingly heavy rains were not only flooding streets, but also pushing water into homes. Action was needed. It seemed like a no-brainer.

Today, forensic engineers investigating the levee breach that flooded much of city during Hurricane Katrina aren't so sure. The search for the cause of the failure keeps returning to that dredging project as the probable starting point for a series of mistakes engineers think ultimately led to the breach.

Among other problems, they say, the dredging sharply reduced the distance water had to travel to reach the canal wall, left the canal too deep for sheet pilings that were suppose to cut off seepage, may have removed some layers of clay that sealed the canal bottom, and reduced support for the wall on the New Orleans side.