A little more than a week after Hurricane Katrina passed to the east of New Orleans and her counterclockwise winds whipped Lake Pontchartrain with enough force to breach the citys levee system in several places, the Army Corps of Engineers finally had good news. The Corps and its contractors plugged the worst leak and started a large pump station that was pushing water through the 17th St. Canal back into the lake. The Corps also reported progress on other major breaches at the London Canal and the Inner Harbor Navigational Canal.
|Gaining Ground. Map in Corps of Engineers command center in Baton Rouge tracked battle plan and progress for repairing broken levees (top) and "unwatering" New Orleans.|
Officials now surmise that as the storm surge overtopped the flood walls at 17th St. and London Canals, it scoured their earthen foundations, causing panels to blow out. At the Inner Harbor Navigational Canal, aerial photographs show a barge nearly as long as one of two breaches in the canals east wall, indicating the vessel may have struck the wall, causing it to fail. "But we cant really be sure until we can inspect the sites and do a forensic analysis of the cause of failure. It could well be that there were multiple causes for the failures at different places," says a weary Alfred C. Naomi, a hurricane protection system project manager who has been working on a drainage planthe Corps calls it unwateringsince the storm pierced city flood walls. Naomi is among a cadre of approximately 60 people from the Corps New Orleans District who have been putting in 12 to 16-hour days in a "war room" in the Corps Mississippi Valley District headquarters in Vicksburg.
Some construction crews are slowly regaining access that will enable them to plug remaining breaches. Others have deliberately cut levees to the south and east: two in St. Bernard Parish and two more in Plaquemines Parish. The fissures allow water trapped by levees to flow out and reach a state of equilibrium with water outside the perimeter.
"I believe that we may have turned a corner last night," Naomi said Sept. 6. By Aug. 31, about 80% of the city was submerged. On Sept. 6, the Corps reported 60% was submerged.
Official estimates for the time required to drain New Orleans range from 24 to 80 days. Naomi is optimistic that, barring another major storm event, the job wont take that long. "Once we get more pumps going, youll see the water level drop rapidly," he says. "I think much of the city will be drained within weeks."
On Sept. 5, the Corps stopped the hemorrhaging from the 17th Street Canal. For days, Chinook and Black Hawk helicopters had been placing large sandbags in the hole. The sandbags broke the surface of the water on Monday. Local contractor Boh Bros. Construction LLC was working simultaneously to plug the breach with rip rap from the north and to close the canal mouth with sheet piles. The contractor left a 40-ft gap in the center of the canal, Naomi says. "We want to keep the pressure off the side walls. We dont really know what the structural integrity is until we can inspect them, so well drain along the center line." That will minimize pressure on the intact west wall of the canal and the repaired east wall, he says.
The Corps placed portable pumps behind the sheet piles to get the flow moving. At the opposite end of the canal, the Sewerage & Water Board is powering up the No. 6 pump station. It is the largest station in the system, rated at 9,380 cu ft per second. "Well pump slowly at first. We dont want to put too much pressure on the canal walls," says Greg Breerwood, Corps deputy district engineer. If the canal walls hold, the plan is to pull the sheet piles and push more water back into the lake.
As levees are repaired and the pump-out draws down the water, the sewerage board and the Corps 249th "Prime Power" Engineer Battalion will repair additional pumping stations. Ten out of about 35 pumps in affected areas of the city are now operating, says the Corps.
With 17th Ave. draining, the Corps and contractors reported they had sheetpiled shut the mouth of the London Ave. Canal, except for a small gap to allow some drainage. Boh Bros. is building an access road and helicopters are sealing a breach there. Pumping will commence as soon as the canal is sealed.
Further east, the Inner Harbor Navigation Channel has one pump running, but also has two long breaches on its east side. Repairs are under way. Beyond that are some of the worst hit areas, East New Orleans, St. Bernard Parish and Plaquemines Parish. While crews were sandbagging and sheetpiling shut the drainage canals that flow into Lake Pontchartrain, the Corps dispatched snagging and grading crews from the Memphis District to purposely breach levees. One of the units normal roles is keeping navigation channels clear in the Mississippi River.
|Hemorrhage. Boh Bros. stopped the flood at the 17th Street Canal by driving a line of sheet piles in the east wall to seal it from the lake.|
They have tracked backhoes called "marsh buggies," says Breerwood. On Sept. 4 and 5, they cut 30-ft notches in the levees in St. Bernard and Plaquemines parishes. The pressure of escaping water soon widened the gaps to 400 ft. By Monday, water on both sides of the levee was approaching a state of equilib-rium. "Now we have to do thorough inspections and close up the levees, strengthen them where theyre weak," Naomi says. "We wont really know what weve got until we do that."
After a terrible week, Corps staffers in the war room in Vicksburg felt slightly upbeat about what they were hearing from the front line. Slowly, they seem to be gaining the high ground. Communications seem to be getting better and a few more people are making their way to the New Orleans District office every day. Seven or eight rode out the storm in a bunker, Naomi says. By Sept. 6, about 100 employees had returned to New Orleans headquarters, all that available conditions can support. "But our drawings are intact and the building came through in pretty good shape," he says.
There is a long way to go, Naomi says. Even if the water drains more quickly than predicted, the business of counting the dead, restoring water and sewerage, dealing with the massive biohazards that are present and beginning the long process of rebuilding will tax even the most optimistic people in a region known for its resilience.
(Photo top by AP/Wideworld, bottom by Michael Goodman For ENR)