Levee Repairs to Be Finished By First Day of Hurricane Season
📅 Thu February 02, 2006 - Southeast Edition
Matt Crenson, AP WRITER
NEW ORLEANS (AP) In New Orleans, the apocalyptic clock is ticking — again.
Ravaged last year by one hurricane and slapped by the fringes of another, the city faces a 2006 storm season that begins in less than five months — not much time to repair the tattered ramparts that keep New Orleans from being swallowed by the sea.
This year’s hurricane season begins June 1. By that date, the U.S. Corps of Engineers expects to have the Crescent City’s levees restored to pre-Katrina condition.
The job is massive. It will take approximately 4 million cu. yds. (3 million cu m) of fill — a nearly Superdome-sized pile — to repair the 170 mi. (274 km) of levee destroyed or damaged by Katrina.
“So far we’re on schedule and we’re doing pretty good,” said Col. Lewis Setliff, the leader of the repair effort.
There are many who fear that may not be good enough.
“This is just a few Band-Aids, really,” said Ivor van Heerden, a civil engineer of Louisiana State University. “We really need to go the step further and start implementing projects now that would make New Orleans safe.”
Setliff said he understands such concerns. But as commander of Task Force Guardian, his mission is to repair the levees in time for the next hurricane season, and that is what he vows to do. New Orleans will simply have to live through 2006 with roughly the same protection it has had for the past 30 — even though that wasn’t enough to fend off Katrina.
“Everybody wants a lot of the long-term solutions overnight,” Setliff said, but there is neither time nor funding to make major improvements to the barriers by June.
The $1.6-billion repair effort will use some improved construction methods and materials compared to what was in place before, decreasing the chances that levees breached by Katrina will fail again. It also will bring levees that had gradually settled over the years back up to their original height.
But it will not raise the height of any levees or replace any sections that survived Katrina intact.
“We don’t have the authority to just go in there and raise levees,” Setliff said. “We are allowed to make some smart decisions.”
For example, in every situation where it can, the Corps of Engineers is replacing the I-walls that top many levees with more stable T-walls. An I-wall is a vertical concrete barrier anchored to the levee by steel sheet pile driven vertically into the ground.
A T-wall sits on a horizontal concrete base that protects the soil at the wall’s base from crashing waves on the wet side and, in a worst-case scenario, from water pouring over the levee onto the dry side. During Hurricane Katrina soil erosion underneath floodwalls — known to engineers as scour — contributed significantly to a number of breaches by simply washing away the ground the concrete barriers sat on.
To make them even stronger, T-walls also are anchored by multiple steel beams, rather than a single sheet. Those beams are driven into the levee diagonally, providing more support.
Most challenging to repair are the breaches along the drainage canals that carry rainwater from the heart of New Orleans north to Lake Pontchartrain. Because so much of New Orleans is below sea level, pump stations have to lift water from the city’s storm sewers into the canals, which then flow by gravity to Lake Pontchartrain.
During a hurricane, the lake’s surging waters reverse the flow in the canals, pushing water deep into the city. Floodwall-topped levees along the canals rise as high as 14.5 ft. (4.5 m) above sea level, which should have been enough to contain Hurricane Katrina. But at three points on the London Avenue and 17th Street drainage canals, the floodwaters weakened the structures to the point that they gave way.
An emergency repair effort plugged the three breaches with massive sandbags weighing as much as 15,000 lbs. (6,800 kg) each. But now the Corps is faced with the tricky task of removing the sandbags and replacing them with a new levee and floodwall — without inundating the city.
What they do is build temporary walls on both the canal and land sides of each breach. This completely surrounds the work area and keep soil from collapsing into the hole that will be created during the next step, when the emergency sandbag levee is removed.
Finally, a new levee and floodwall is built across the breach. After the new T-wall has been completed, the temporary walls, known as coffer dams, will be removed.
“This job will go right up to June,” construction inspector Duke Ducarpe said of the repair at the 17th Street Canal breach. He said the two breaches on the London Avenue Canal might be repaired a few weeks earlier than that.
Because the canals were so vulnerable after Hurricane Katrina, the Corps of Engineers is considering additional measures to protect them. If a hurricane does approach New Orleans next year, the plan is to erect temporary gates or barriers at the mouths of the canals that would protect them from storm surges coming off Lake Pontchartrain.
But that would impede the flow of water out of New Orleans, which could be a problem if a hurricane dumped a lot of rain on the city.
“If you got a very serious rainfall, then you wouldn’t be able to operate the pumps because the canals are blocked,” van Heerden said.
He complained that in other areas, the Corps simply isn’t doing enough. In many places, Katrina’s storm surge overtopped an earthen levee and then began wearing it down, allowing an ever increasing amount of water to surge through the breach.
Along the Inner Harbor Navigation Canal, the torrent grew so powerful that it swept away much of the Lower Ninth Ward neighborhood, washing entire houses off their foundations and sending cars tumbling like pebbles in a raging river. The Corps plans to replace the I-wall along the canal with a T-wall.
Such measures may be enough to protect the Lower Ninth Ward during another Katrina. But there will be no improvement of levee segments that did not fail during last summer’s storm. That leaves some of those segments as the most vulnerable points next time a hurricane hits, unless additional, costly efforts are made to beef up the entire levee system.
The Interagency Performance Evaluation Task Force, one of several teams of engineers reviewing the performance of the flood control system during Hurricane Katrina, intends to determine just how much protection New Orleans will have once its levees are repaired. The question is a difficult one, said Ed Link, the University of Maryland professor who heads the team, and it won’t be answered until June 1.
Donald Powell, named by President Bush as the federal coordinator for the Gulf Coast rebuilding effort, has proposed spending an additional $1.5 billion to provide more protection.
The proposal would allow for several improvements, including:
• The completion of levee projects to the south and east of New Orleans that had been authorized before Katrina but were not scheduled to be finished until 2018.
• Armoring levees with pavement or rock to prevent waves from eating away at them.
• Closing the drainage canals and installing pumps on Lake Pontchartrain to remove rainwater from the city.
So far Congress has approved the first item on that list. But it balked at armoring the levees and installing new pumps, objecting that those measures had not been adequately examined.
Even if Congress does approve the Bush plan when it reconvenes in February, will it be enough to coax displaced residents and businesses back to New Orleans?
Civil engineer van Heerden doesn’t think so. He thinks Washington should spring for a major flood control system that raises the levees around New Orleans and other communities in south Louisiana high enough to survive a direct hit by a Category 5 hurricane — the top of the scale. Katrina had weakened to Category 3 or less by the time it passed through the city.
Van Heerden also recommends building structures that knock down incoming storm surges in the Gulf of Mexico, before they pass into the bays and harbors on New Orleans’ flanks. Finally, van Heerden advocates a massive effort to rejuvenate the marshes that once buffered the city from the Gulf’s open waters. Those wetlands have gradually succumbed to channelization, pollution and sediment starvation over the years, mostly because of efforts to improve shipping and prevent floods on the Mississippi River.
Such an effort could easily cost more than $30 billion.
“We’ve really got to look at doing more,” van Heerden said.
Democratic Congressman William Jefferson, who represents New Orleans, considers the Bush administration’s proposal a “down payment” on a full-fledged system that would protect New Orleans from a Category 5 hurricane.
“What is going to be most important to people is whether they can come back and rebuild with some security,” Jefferson said during a Jan. 6 special session of the New Orleans City Council. “Otherwise we will suffer a depopulated city for some time to come.”