Thursday, May 22, 2008

Despite Improvements, New Orleans Canal Still Leaks; West Bank Lags Behind

With hurricane season just days away, MSNBC has posted two articles that highlight disturbing vulnerabilities in New Orleans' hurricane protection systems.

In one
the Associated Press reports:

Despite more than $22 million in repairs, a levee that broke with catastrophic effect during Hurricane Katrina is leaking again because of the mushy ground on which New Orleans was built, raising serious questions about the reliability of the city's flood defenses.

Outside engineering experts who have studied the project told The Associated Press that the type of seepage spotted at the 17th Street Canal in the Lakeview neighborhood afflicts other New Orleans levees, too, and could cause some of them to collapse during a storm.

The Army Corps of Engineers has spent about $4 billion so far of the $14 billion set aside by Congress to repair and upgrade the metropolitan area's hundreds of miles of levees by 2011. Some outside experts said the leak could mean that billions more will be needed and that some of the work already completed may need to be redone.

"It is all based on a 30-year-old defunct model of thinking, and it means that when they wake up to this one — really — our cost is going to increase significantly," said Bob Bea, a civil engineer at the University of California at Berkeley.

The 17th Street Canal floodwall collapsed on the day Katrina surged over New Orleans in August 2005, and the failure severely damaged Lakeview. It was one of the biggest of about 50 levee breaches that contributed to the deaths of about 1,300 people.

Fixing the 17th Street Canal has been one of the most expensive and laborious repair jobs since the storm and has served as something of a test case for scientists and engineers, who plan to apply the lessons learned there to the city's other levees.

Among other things, they repaired the wall by driving interlocking sheets of steel 60 feet into the ground, compared with about 17 feet before the storm. The sheet metal is supposed to prevent canal water from seeping under the levee through the wet, toothpaste-like soil that lies beneath the city, which was built on reclaimed swamp and filled-in marsh.

Over the past few months, however, the corps found evidence that canal water is seeping through the joints in the sheet metal and then rising to the surface on the other side of the levee, forming puddles and other wet spots.

Engineers said the boggy ground is a more serious problem than the corps realizes. Bea said there is a roughly 40 percent chance of the 17th Street Canal levee collapsing if water rises higher than 6 feet above sea level. During Katrina, the water reached 7 feet in the canal.

John Schmertmann, a retired University of Florida professor and a consultant on foundations, agreed with Bea that the corps "may still be embedding some of these not-properly-considered factors, so the new walls may not do what the corps expects."

Reducing such seepage might require the driving of sheet metal far deeper into the ground than is done now, or some other solution, said Bea, who was part of a team of experts sent by the National Science Foundation to do an independent study of the levee failures during Katrina.

In another MSNBC post, Reuters reports:

Post-Katrina New Orleans remains two separate communities as another hurricane season begins on June 1.

On the city's East Bank, the U.S. Army Corps of Engineers is raising levees and installing steel-reinforced gates on three drainage canals to block a surge in Lake Pontchartrain from pushing into the canals, as occurred in 2005.

Lt. Col. Murray Starkel, the Corp's deputy commander in New Orleans, said the reinforced gates will protect the canals against a surge during a Katrina-like storm that might occur once every 100 years.

That once-in-100-year-event has become the Corps' minimum standard for New Orleans' flood protection.

"I think the inner portion of the city of New Orleans is better protected than it has been in many, many years," said Jerry Sneed of Louisiana's Office of Homeland Security and Emergency Preparedness. "Is it at the 100-year storm level? Not yet, but it will be in the near future."

The other side of the river is a different story.

About $285 million in improvements on West Bank levees and floodwalls won't be completed for another year.

That system will only meet standards set more than two decades ago, said Gerald Spohrer, executive director of the West Jefferson Levee District. Reaching 100-year storm protection will take at least three more years, he said.

The West Bank, much of which lies south of downtown New Orleans, is at greater risk than the rest of the city because it is more exposed to the Gulf. It came through Katrina relatively unscathed only because the storm jogged eastward just before landfall.

"The West Bank is still vulnerable," Sneed said. "Our biggest fear is that people who live on the West Bank of New Orleans and didn't get flooded think that they are home free in the event of a storm."

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