Engineers race to fix levees five
months before storm season
11:10 AM CST on Saturday, January 14, 2006
By MATT CRENSON / Associated Press
In New Orleans, the apocalyptic clock is ticking —
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
The job is massive. It will take about 4 million cubic
yards of fill — a nearly Superdome-sized pile — to
repair the 170 miles of levee destroyed or damaged by
"So far we're on schedule and we're doing pretty good,"
said Col. Lewis Setliff, the leader of the repair
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 at Louisiana State University.
"We really need to go the step further and start
implementing projects now that would make New Orleans
Setliff says 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
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 will also 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 so-called "I-walls" that
top many levees with more stable "T-walls." An I-wall is
simply 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 are also anchored by
multiple steel beams, rather than a single sheet. Those
beams are driven into the levee diagonally, providing
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 1/2 feet 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 pounds
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. The Corps plans to
erect temporary gates at the mouths of the canals to
protect them from storm surges coming off Lake
Pontchartrain. The gates will be open during good
weather, but if a hurricane does approach New Orleans
next year, they can be closed at a moment's notice.
Van Heerden 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
The proposal would allow for several improvements,
_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
Democratic U.S. Rep. 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."