The Corps of Engineers has been claiming the floodwalls that failed in New Orleans during Hurricane Katrina performed according to specifications and that the failures were due to the storm conditions exceeding the design specs. However, Engineer Manual No. 1110-2-2502 quashes that claim.
"It says what every engineer knows: If you build walls to 14 feet, regardless of the design specifications for the expected storm -- 12 feet or 10 feet or 13 feet -- those walls must hold water to their tops," said J. David Rogers, a forensic engineer on the National Science Foundation team investigating the failures.
"That's a basic rule in engineering, whether you're building dams or floodwalls. And those floodwalls were 14 feet in New Orleans, and all the evidence says they weren't overtopped.
"So, yeah, this was a human failure, not a natural disaster."
Section 4b of the manual reads: "Case I2, Water to the Top of the Wall. This is the same as Case I1 (design flood loading) except the water level is at the top of the unprotected side of the wall."But the Corps is still stuck on stupid:
(T)he corps commander, Brig. Gen. Carl Strock, said his agency believes Katrina was a Category 4 storm when it made landfall at Buras, and was a Category 5 when it was building storm surge in the Gulf that later fell on Louisiana. Corps officials say that the floodwalls and hurricane levees were designed to withstand the equivalent of "a fast-moving Category 3 storm."
But when Congress authorized the Lake Pontchartrain and Vicinity Hurricane Protection project in 1965, the now-familiar system of ranking hurricane intensity by Categories 1-5 was not in use. Instead, the corps was directed to protect the city from what the National Weather Service called the "Standard Project Hurricane." This is a once-in-300-years storm with maximum sustained winds of 100 mph in a 30-mile radius around the eye, traveling at an average speed of 6 mph, creating a storm surge on the south shore of Lake Pontchartrain of 11.5 feet.
Investigators believe the storm-surge reached a height of 10.5 feet before the floodwalls failed, one foot below the height mandated by Congress and 3.5 feet below its designed height.
So Engineer Manual No. 1110-2-2502 is the "Go Directly To Jail" card for the engineers. It doesn't matter what Congress mandates the Corps to build, it still has to comply with engineering standards. If a client hires me to design a three-story building without exit stairs and I build it, I'm at fault for not complying with the Life-Safety Code. God help us if people die in a fire in that building.
The Corps of Engineers must think it operates under its own rules.