Bailing Out City Starts With a Patch Job on Levees

Black Hawk helicopters dropped 1.5-ton sandbags to plug a gaping hole in a canal wall Thursday as the Army Corps of Engineers began planning to bring in new pumps to replace those damaged by the flooding in New Orleans. It was the first indication that the city’s vital network of 22 pumps is seriously damaged.

With water levels finally subsiding, U.S. military helicopters began filling two of the three levees torn open by Hurricane Katrina, at the 17th Street Canal and London Avenue Canal. At the 17th Street waterway, crews built a dam of corrugated steel to prevent water from entering the canal.

The repair jobs, which corps officials said might be finished as early as today, would be the first step in the mammoth task of pumping water out of the city, about 80% of which is still submerged.

“We’re going to try draining a very large, 30-foot-deep lake,” said Col. Richard Wagenaar, the corps’ senior official in New Orleans. “We’ve done nothing like this before.”

The complexity will be enormous, he said, acknowledging that rain or other foul weather could easily derail any well-laid plan. “It could easily change,” he said.

But for now, Wagenaar said the corps is focused on repairing the levees, one of which has a two-block-long gap, and punching holes in other parts of the canal walls to drain enough water out of the city to allow water pumps to operate. Engineers surveyed levees by helicopter Thursday and will begin identifying where to make the holes. The size of the holes will also have to be carefully planned because they will have to be repaired once the city is drained, Wagenaar noted.

The city’s design contributed to the unusually expansive nature of the flooding. Much of New Orleans is below sea level and rests within a bowl formed by levees, locks and floodgates that control water flow through and around the city. A system of 22 pumping stations expels rainwater through 4-foot-wide pipes.

But many of the pumping stations are under water and will not be repairable, said Wagenaar, who surveyed New Orleans by helicopter Thursday and found six of the pumps submerged. Moreover, most of the city’s power lines were knocked down by winds that reached 140 mph.

Wagenaar said the corps would buy new pumps that could be flown in by helicopter or trucked in if possible and then attached to existing pipes. Electricity would come from diesel generators operated by the Army.

Pumping out the water could take three to six months depending on the weather, Wagenaar said. “Think of every hurricane we’ve had and then throw another 10 feet of water on top of it. There is a lot of water here.”

But Charles Dowding, professor of civil and environmental engineering at Northwestern University, said the estimates probably were overblown.

“It is an estimate he is giving so he can beat it,” Dowding said. “If I were him, I’d do the same thing. I would give as bleak an estimate as possible. Why not? Your tail is already dusted off.”

Dowding was involved in a massive $500-million project in the late 1990s to upgrade the levees and pumps in New Orleans. At the time, he estimated that the new pumping system would be capable of removing a foot of water per day across Jefferson Parish, and he believed that the same capacity existed in Orleans Parish.

Although the floodwaters may be 30 feet deep or more in some places in the city, Dowding said, he doubted seriously whether that was the average depth. As a result, it would suggest that if the pumps had been working, the water could be removed in less than four weeks, he said.

But Dowding acknowledged that the fixed pump stations were no doubt inoperable after being submerged. The on-site emergency generators would be ruined, as would the electric motors operating the pumps, he said. The pumps are massive machines, fixed in heavy concrete foundations.

“You are not going to find pumps like these at your Home Depot,” he said. “These are more like turbines.”

The portable electric generators and pumps that the Army Corps will bring into the city will probably have a much lower capacity than the fixed pumps, he said. That could be one reason the corps is estimating it will take three to six months to remove all the water.

What’s more, once the new pumps are working, they will have two tasks. Even in normal times, the New Orleans drainage system must work around the clock to remove water that seeps in through levees and through the ground from Lake Pontchartrain and the Mississippi River.

David Schulz, director of the Infrastructure Technology Institute at Northwestern, said punching holes in the levees to drain water could pose complications.

And even once the city is pumped dry, water damage to homes will be significant, said Greg Axten, a geotechnical engineer with American Geotechnical Inc. in Yorba Linda, which investigates structural problems with homes.

“With a rare exception, the homes will be a total loss,” Axten said. “It’ll be cheaper to knock them down than trying to save them.”