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Moving Toward Drying Out
Marcuson explained that New Orleans has a compartmentalized flood control system, in which an internal system of floodwalls and levees divides the city into a series of cellarlike sections, which are drained during storms by dedicated pumps. "Think of it like a set of basements with sump pumps in each one," he said.
The second reason for the receding water was that the lake had subsided so much that the water inside the city was able to flow back the way it had come. The 17th Street and London Avenue breaches became drains. By yesterday afternoon, 53 percent of the city was dry.
Anderson said the Corps planned to leave the 250-foot-wide London Avenue break alone so water would continue to flow out, and that "notches" are being cut in the levee protecting eastern New Orleans -- makeshift gutters so water will spill out.
But if the city relied only on gravity, months would elapse and there would still be two feet of water on the ground. Engineers needed to get pumps working in the areas of heavy flooding, and to do that, they needed to close the 17th Street breach.
For three days, Corps officials had lamented the difficulty of gaining access to the canal, but yesterday a local contractor, Boh Bros. Construction Co., apparently drove to the mouth of the canal and started placing a set of steel sheet pilings to isolate the canal from the lake. This job was finished yesterday afternoon.
Only then, Louisiana Secretary of Transportation and Development Johnny B. Bradberry explained, would the canal water subside enough that Boh Bros. could get to the breach itself and start driving piles there to fill it. Anderson said this began yesterday evening.
Bradberry said the breach would be plugged by tomorrow. Then the pilings at the canal mouth would be removed to allow nearby pumps to discharge to the canal, which would carry the floodwater out to the lake and eventually into the Gulf. Where necessary, diesel-powered generators will be brought in to drive the pumps.
Anderson cautioned that pumping may not begin immediately, if pumps are damaged or wet, but Bradberry envisioned no problems: "We can't wait to press the button," he said. "The pumps are ready to go."
Gugliotta reported from Washington; Whoriskey, from Baton Rouge, La.