NEW ORLEANS (AP) - Seven years ago, the Army Corps of Engineers was desperately trying to plug breaches in the city’s broken and busted levee system.

Since those catastrophic days, the Army Corps has worked at breakneck speed - and at a cost of billions of dollars - to install new floodgates, pumps, floodwalls and levees across New Orleans. The work paid off. A day after Isaac hit New Orleans on the seventh anniversary of Katrina, officials said the 130-mile flood protection system did its job.

“If I had to give it a grade, I would give it an A-minus, and only a minus because of the small challenges we had,” said Tim Doody, the president of the Southeast Louisiana Flood Protection Authority-East, a commission that oversees levees protecting New Orleans.

The only problem came at the 17th Street Canal, the site of a breach during Katrina. When computers that are supposed to turn on pumps failed there Wednesday. Pump operators had to turn them on by hand, causing a delay of an hour or two, Doody said.

Getting the pumps to work is critical.

The 17th Street Canal is one of three major drainage canals the city pumps rain into and flushes out to Lake Pontchartrain. When Katrina hit, those drainage canals proved to be fatal as surge from the lake rushed into them and broke through poorly designed floodwalls. The breaches caused much of the flooding of the oldest sections of New Orleans.

To prevent that from happening again, the Army Corps installed new floodgates and pumps at the mouth of the drainage canals to block water from coming in. The corps’ pumps must also be able to keep up with the city’s pumps or water gets backed up.

Rachel Rodi, a corps spokeswoman, said having to turn pumps on by hand was not a big deal. “I wouldn’t say it was an issue,’” she said.

A day earlier, a floodgate at another drainage canal, the Orleans Avenue Canal, had to be shut with a crane. That too was not serious, she said.

During Isaac, the corps used for the first time in the face of a hurricane some of the system’s biggest new structures.

It closed two large floodgates that cut off surge from entering the Inner Harbor Navigation Canal, a place long considered an Achilles’ heel in the city.

It also closed and operated a floodgate and pumping system on the West Bank, a suburban area of the city on the opposite side of the Mississippi River from the French Quarter.

Isaac brought storm surge that reached up to 14 feet in the area around the Inner Harbor Navigation Canal, just 2 to 3 feet shy of what Katrina pushed in.

“If that surge barrier had not been there, the story would have been a very different story,” Doody said.

The corps is not done with its work.

So far it has spent about $10 billion of the $14 billion Congress set aside. The corps plans to build bigger and stronger floodgates and pumping stations at the three drainage canals and armor the entire system with concrete.

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