By Andrew G. Wright From enr.construction.com
About a week after Hurricane Katrina passed to the east of New Orleans, with her counterclockwise winds whipping up Lake Pontchartrain with enough force to breach the city's levee system in several places, the Army Corps of Engineers finally had some good news.
The Corps and its contractors had plugged the worst leak and started a large pump station that was pushing water through the 17th St. Canal back into the lake. Water was finally flowing out of, not into, the Crescent City.
"TURNED A CORNER." Progress is also being made on other major breaches at the London Canal and the Inner Harbor Navigational Canal. While construction crews are slowly regaining access allowing them to plug the remaining breaches, others have deliberately cut levees to the south and east: Two in St. Bernards Parish and two more in Plaquemines Parish. The fissures allow water trapped inside levees to flow out and reach a state of equilibrium with the water outside the perimeter.
"I believe that we may have turned a corner," says Alfred C. Naomi, a hurricane protection system project manager who has been working on a drainage plan -- the Corps calls it unwatering -- since the storm pierced city floodwalls.
Naomi is among a cadre of about 60 people from the Corps' New Orleans District who have been putting in 12- to 16-hour days in a "war room" in the Corps' Mississippi Valley District headquarters in Vicksburg.
LACK OF POWER. This war's omnipresent foe, of course, is water. By Aug. 31, an estimated 80% of the city was submerged. The estimate for the amount of time required to drain it ranged from 30 to 80 days.
Naomi is optimistic that, barring another major storm, the job won't take that long. "Once we get more pumps going, you'll see the water level drop rapidly. I think much of the city will be drained within weeks."
But to do that, the pumps need power. Entergy (ETR), the utility that provides power to New Orleans, reported on Sept. 5 that it had energized substations serving the Central Business District and the French Quarter. But, for safety's sake, the utility had crews checking individual buildings before it provided electricity.
BRAKING THE SURFACE. Entergy was concentrating on power restoration to the Sewerage & Water Board's system pumping stations in the Lakeview section, near the 17th St. Canal. Water in this district remained up to rooflines, but on Sept. 5, the Corps plugged a 450-foot breach in the canal wall. For days, Chinook and Black Hawk helicopters had been placing large sandbags in the hole. The sandbags rose above the surface of the water on Monday.
But the Corps wasn't in this fight alone. Local contractor Boh Bros. Construction was working simultaneously to plug the breach with rip rap - stones and chunks of concrete -- from the north and to close the canal mouth with sheet piles, thick slabs of metal pounded into the ground to form a wall.
The contractor left a 40-foot gap in the center of the canal, Naomi says. "We want to keep the pressure off the side walls. We don't really know what the structural integrity is until we can inspect them, so we'll drain along the center line." That will minimize pressure on the intact west wall of the canal and the repaired east wall, he says.
SEALING BREACHES. The Corps placed portable pumps behind the sheet piles to get the flow moving. At the opposite end of the canal, the S&WB is powering up the No. 6 pump station. The largest station in the system, it has a rated pumping capacity of 9,380 cubic feet per second.
"We'll pump slowly at first. We don't want to put too much pressure on the canal walls," says Greg Breerwood, the Corps deputy district engineer. If the canal walls hold, the plan is to pull the sheet piles and push more water back into the lake. Other pump stations will come on line as fast as S&WB and the Corps' 249th Prime Power Engineer Battalion can get them ready.
With 17th St. draining, Corps and contractor reported that they had sheetpiled shut the mouth of the London Ave. Canal, except for a small gap to allow some drainage. Boh Bros. is building an access road, and helicopters are sealing a breach there. Pumping will commence as soon as the canal is sealed.
MARSH BUGGIES. Further east, the Inner Harbor Navigation Channel has a pump running, but it also has two long breaches on its east side. Repairs are under way. Beyond that are some of the worst hit areas: East New Orleans, St. Bernard's Parish and Plaquemines Parish.
While crews were sandbagging and sheetpiling shut the drainage canals that flow into Lake Pontchartrain, the Corps had dispatched snagging and grading crews from the Memphis District, to purposely breach levees.
One of the unit's normal roles is to keep navigation channels clear in the Mississippi River. They have tracked backhoes called "Marsh Buggies," says Breerwood. On Sept. 4-5 they cut 30-foot notches in the levees in St. Bernards and Plaquemines Parish. The pressure of escaping water soon widened the gaps to 400 feet.
QUEST FOR BALANCE. By Sept. 6, Naomi says, water on both sides of the levee was approaching a state of equilibrium. "Now we have to do thorough inspections, and close up the levees, strengthen them where they're weak. We won't really know what we've got until we do that," he says.
After a terrible, terrible week, the folks in the war room in Vicksburg felt slightly upbeat about what they were hearing from the troops on the front line. Slowly, they seem to be gaining the high ground. Communications seem to be getting better. A few more people are making their way to the Corps' New Orleans District office every day. Seven or eight rode out the storm in a bunker, Naomi says.
By Sept. 6, about 100 employees had returned to New Orleans headquarters -- all that available conditions can support, he says. "But our drawings are intact, and the building came through in pretty good shape."
But there's a long way to go, Naomi admits. Even if the water drains more quickly than predicted, the business of counting the dead, restoring water and sewerage, dealing with the massive biohazards, and starting the long process of rebuilding will tax even the most optimistic souls in a region known for its resilience.
It may not be an actual war, but the Corps - and a flood-battered city - is still in for a lengthy fight.
Read additional Hurricane Katrina coverage from McGraw-Hill Construction
Wright is a senior managing editor for McGraw-Hill Construction