NEW ORLEANS -- Just three years after Hurricane Katrina, New Orleans confronts a new threat from Gustav and a stark question: Will the partially rebuilt levees hold?
Despite $2 billion in improvements, including 220 miles of repaired, raised and replaced floodwalls, 17 new pump stations and more flood-resistant pump stations, nobody can say for sure the city won't be swamped again. And if it is, could it ever recover?
"It's scary, man," said Robert Russell, a 63-year-old plumber whose house in Gentilly Woods is close to floodwalls on the Industrial Canal that are so suspect the U.S. Army Corps of Engineers is buffering them with large baskets filled with sand.
"They say it's not up to code," he said. "We'll have to wait and see."
Levee experts and the corps insist New Orleans is safer than before Katrina flooded more than 80 percent of the city Aug. 29, 2005.
Yet the system still has severe shortcomings: Flood barriers meant only to withstand medium-strength storms, hidden layers of weak soil and navigation channels that inadvertently funnel storm surge into the city, to name a few.
"The positive thing about having any storm hit you, it will reveal any kind of frailty in the system," said J. David Rogers, an engineer at Missouri University of Science and Technology, who's tracked the construction closely. "And we shouldn't be surprised if there is frailty."
Experts estimate the system is only a third of the way to where the corps wants it by 2011 -- strong enough to protect against what scientists call a 100-year-storm. That type of hurricane has a 1 percent chance of occurring each year.
By comparison, the corps says Katrina was a 396-year storm, a rare catastrophic hurricane. The agency has not classified Gustav, which was spinning Thursday near Jamaica and already lashing the island with tropical storm-force winds.
"We're not close to 100-year-level protection yet," said Robert Turner, the regional director of the Southeast Louisiana Flood Protection Authority-East. "It's not worth putting your life at risk if you have the means to get out."
Each side of the river still has its own problems.
On the east side, where the French Quarter stands, the most serious concerns lie along a T-shaped shipping corridor where the Industrial Canal meets the Gulf Intracoastal Waterway. The canals have been the cause of repeated flooding over the decades, and floodwalls along it were breached during Katrina, flooding the Lower 9th Ward, Gentilly, St. Bernard Parish and eastern New Orleans.
Corps officials have called it the system's Achilles' heel. To fix the problem, the agency plans to spend at least $695 million to construct a barrier across the shipping channel's mouth. But that work won't be done for at least another three years.
There are other spots to watch, too.
Levees protecting eastern New Orleans and St. Bernard Parish are in many stretches 10 feet lower than what the corps would like them to be, Turner said.
Another concern is a new system of pumps and floodgates on three drainage canals. Floodwalls on two of the canals collapsed during Katrina, causing widespread flooding in central New Orleans.
The corps installed the new system to prevent storm surge from entering the canals, but some of the pumps have been plagued with problems. They were defective when they were installed in 2006 and doubts persist about the corps' overall engineering solution.
The other side of the Mississippi, known as the West Bank, has serious flaws as well.
In the past two years, the corps has been scrambling to finish its work. But levees, floodwalls and floodgates remain in various states of completion.
At the moment, four miles of floodwall are under construction, and corps contractors are working to raise 23 miles of levees, the corps said.
In time, the corps would like to build a massive floodgate to stop storm surge water from entering canals that run through the West Bank.
But for now, those are just ideas.