On the canal's west side, where the levee was intact, a small clutch of gawkers perched on the flood barrier, oohing and aahing as heavy-lift helicopters thudded overhead to drop immense white bags filled with sand into the 300-foot gap that Hurricane Katrina had carved in the opposite flood wall.
On the east side, New Orleans police Officer David Hunter chugged quietly along in his motorboat looking for refugees and pointing out the sights in the Lakeview neighborhood where he once lived. His own house, submerged nearby in 20 feet of water, was "inaccessible," he said.
"But there's my friend Sal's house -- been on the force 30 years." He pointed at a tile rooftop and dodged as a stoplight went by at eye level: "On the right is the Basin bar. I'd buy you a beer, but I don't think it's open."
This is the epicenter of one of the biggest natural disasters in U.S. history -- an ordinary middle-class New Orleans neighborhood framed by Lake Pontchartrain and the 17th Street Canal, whose levee was breached Monday morning when Katrina's storm surge pushed the lake into the canal until the floodwall gave way.
The Army Corps of Engineers learned that the levee had broken early Monday even as the storm hit, but it was impossible to do anything about it before lake water cascaded unimpeded into the below-sea-level city for 36 hours, turning a really bad storm into an unimaginable abomination. There was no public announcement that the levee had broken until late Monday.
Lt. Gen. Carl A. Strock, the Corps' commander, told reporters at the Pentagon on Friday that Katrina had simply overpowered levees designed 30 years ago with a 99.5 percent chance of enduring for 200 to 300 years: "We, unfortunately, have had that 0.5 percent" happen, Strock said.
On Friday, the Corps was trying to close the 17th Street breach and another breach at London Avenue to the east. A third break -- two breaks actually -- in the Industrial Canal, were left alone because water levels in the lake and the surrounding wetlands had subsided so much that water was draining out instead of coming in.
Col. Richard P. Wagenaar, the Corps' New Orleans District commander who is the on-site commander at 17th Street, said a police officer called him Monday morning to tell him about the break, but he could not drive there. On Tuesday, the Corps tried to drop some sandbags into the breach, but "it didn't work real well," Wagenaar said. "They were too small, and the water velocity carried them away."
It was better on Friday, but there was a big, deep hole to fill, and the bags -- made to hold 20 tons of sand -- were only carrying five, because the helicopters that arrived every five minutes or so, Black Hawks, Sikorskys and even the Chinooks, could not haul more.
Still, the Corps had a plan. Michael Zumstein, action officer for the Corps' "unwatering team," said the canal had been sealed off from the lake with steel slabs, causing water levels in the canal to drop further. That should eventually make it easier to plug the breach.
While the preferred strategy was to plug the breach and allow the city's pumps to discharge floodwater into the canal, the Corps was also prepared to use emergency pumps to flush directly over the steel dam and into the lake if stopping up the hole proved too difficult.
Zumstein said engineers were using the same strategy at a 250-foot breach in the London Avenue Canal, where they were closing the canal mouth even as they tried to stopper the hole: "They're tearing up Lakeshore Drive and using the concrete as fill," Zumstein said.
Elsewhere, flood teams were taking advantage of the fact that the city is divided by internal levees and floodwalls into 13 "sub-basins" with their own drainage systems and pumping stations -- like separate basements with their own sump pumps.
Walter Baumy Jr., engineering chief for the Corps' New Orleans District, said water levels in the lake had subsided by mid-afternoon Friday to within a foot of normal levels, and "when the water inside the bowl is higher than the lake level, we want to drain the water out of the bowl as much as possible."
Baumy said engineers planned to cut new breaches, or "notches" in levees elsewhere in the city, creating makeshift gutters in flooded areas to let water leak out. "We'll see an immediate improvement," he predicted.
But none of this was likely to help David Hunter any time soon. He is 47 -- a mounted officer in the French Quarter who had been planning to file his retirement papers the morning the storm hit: "But I wouldn't be much of a man if I left now. I couldn't live with myself," he said. So he cruises the neighborhood, looking for somebody to help, hoping that no one has died.
There are no fish swimming in Lakeview, and no bayou alligators, he said. The water bubbles with natural gas from broken mains and carries the detritus of a neighborhood to and fro. One neighbor refused to evacuate, and Hunter hasn't seen him. Still, he added, he hasn't found any corpses. At the Basin bar, "we'd sit there and solve all the world's problems, but with this, I just don't know where to begin," Hunter said. "I don't know if this city will ever come back."
Gugliotta reported from Washington. Staff writer Bradley Graham contributed to this report.