Will the levees hold?

When a barge evidently busted the industrial canal levee near Tennessee Street in the fury of hurricane Katrina, it flattened 800 feet of the massive metal walls, causing an enormous wave that wiped out six blocks of homes and destroyed most of this New Orleans East neighborhood.

Today, the breach is patched, at least temporarily. But the levee is weakened for miles, and engineers worry that makeshift repairs - tons of sand that fill the gap, about 10 feet lower than the rest of the levee - won't withstand even a mild wave.

Now, as hurricane Rita steams toward Texas, it isn't hurricane-force winds that scare this city so much as the prospect of buckets of rain.

The Army Corps of Engineers say the levees can handle just 6 inches of rain and a storm surge of 10 to 12 feet.

"If the storm surges come up, this will all wash right into the neighborhood," says Capt. Ron Beaulieu of the New Orleans Fire Department, as he stands on the sand walls of the Industrial Canal patch. He points to the deep trench that formed in the mud along the still-standing levee walls. "All the levees are like this. They're really weakened."

Potential for renewed flooding was on everyone's minds in New Orleans this week as Mayor Ray Nagin halted his ambitious repopulation plan and asked just-returned residents to evacuate again.

Even as New Orleans finally declared itself free of the floodwaters that once covered 80 percent of the city, officials here are bracing for the prospect of more - and hoping that, if the worst does come to pass, they'll be better prepared this time.

Lines of cars with residents hoping to return and clean out their homes have been turned around on I-10. And across the city, the hum of cleanup and response activity is slowing, as everyone from animal rescuers to the National Guard takes stock of Rita's approach.

"Everyone's going to Alexandria [La.] to ride out the storm," says Col. Ken Lull of the Colorado National Guard's169th field artillery brigade. Col. Lull got married Sept. 3 and jokes that he's spending his honeymoon in New Orleans. He's in charge of the task force for the hard-hit St. Bernard Parish. "With this levee out here, we can't be here [if it breaks] - then we become casualties."

Military units across the region repositioned themselves with Rita in mind. Marines who've spent the last few weeks setting up food distribution and cleaning out schools in Mississippi and Louisiana boarded the Iwo Jima ship in downtown New Orleans to ride out the storm and go wherever they might be most needed.

And most of the 1,850 soldiers with the Oregon National Guard, part of a task force responsible for Lakeview, the Ninth Ward, and other severely damaged New Orleans neighborhoods, loaded onto contracted buses to wait out the storm in Alexandria, northwest of the Big Easy.

"They've asked us to be a quick-reaction force for Rita," says Gen. Doug Pritt of Oregon's 41st Brigade. If Rita hits, his unit can go wherever they're needed most, he says, and won't risk being cut off by floods.

Meanwhile, the mayor issued a voluntary evacuation order for the city - and this time, he has 500 buses standing by to take residents out. The Army Corps of Engineers placed a huge steel barrier across the 17th Street Canal bed to ward off another storm surge and ordered that 2,500 more sandbags be ready in case a breach occurred. Workers around the city worked furiously to repair pumps and flood walls. And all faced the fact that it may be years before New Orleans is actually ready to confront another hurricane.

But epic storms aren't the only events that could test the city's defenses. Louisiana is one of the nation's wettest states, and flood-producing rains occur throughout the year. The hope is that Rita will miss, and the drier fall will give engineers time to strengthen the levees.

Engineers are concerned about hidden damage Katrina may have inflicted on the levees. Inspectors "have not had time to conduct detailed inspections of all the levees," says Gregory Reed, who heads the civil and environmental engineering department at the University of Tennessee at Knoxville. "There's no assurance the levees could withstand another event."

Over at the temporary veterinary station, where residents, troops, and rescue workers have brought stray animals for the last few weeks, volunteers ordered to evacuate readied the last truckload of dogs and cats, bound for Florida and Texas. City contractors working with huge cranes to repair buildings in the French Quarter and downtown waited for word on whether to remove their equipment.

In New Orleans East, where all the homes will likely need to be bulldozed, rescue workers continued their grim task of going door-to-door, forcing their way into windows and swollen doors to look for stranded residents or bodies.

"This is the secondary search," explains Janice Matos of the Miami-Dade Fire and Rescue, as workers use sledgehammers - the "master key" - to get into sagging, crushed homes that sit in six inches of drying mud.

As they prepared to pull out, Oregon National Guard troops swapped stories of the last two weeks - the 89-year-old woman they rescued two weeks after the flooding when a night flight spotted the candles she was burning inside; or the two cockatoos that became their last rescue.

"It's been nice to actually work with people and see how much it means to them," says Capt. Kelby McCrae, a young officer from Brookings, Ore., who had been handing out flyers warning of Rita's dangers.

• Staff writer Peter N. Spotts in Boston contributed to this report.