Engineer Manual No. 1110-2-2502 is not a publication that would normally excite interest from the general population. But in the weeks and months ahead, as New Orleans struggles to rebuild from the floods of Hurricane Katrina, Section 4 of that Army Corps of Engineers book could be scrutinized intensely by city and state officials.
The manual sets the performance standards for, among other things, inland floodwalls: the kind the corps built along the city's drainage canals and that failed spectacularly during Katrina, flooding much of the city and leading to many of the 1,100 deaths thus far confirmed from the storm.
...Forensic engineers investigating the levee failures say the layman's translation of that section amounts to a "gotcha" clause for those who believe the walls failed through faulty design and not because they were overwhelmed by a storm that exceeded design limits.
"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.
..."So, yeah, this was a human failure, not a natural disaster."
Since overtopping has been ruled out as the cause of failure along some canal walls, experts in and out of the corps have debated whether the water inside the failed floodwalls was higher than the 12.5 feet maximum listed as the design capacity. But Rogers and other engineers said Section 4b makes that discussion moot. Because the walls were built to 14 feet, to account for wave splash, any collapse below that level means the design failed.
"Their own manual makes it pretty clear this was a failure, " Rogers said, "although they might try to argue it was something else."
...But the debate continues, because the stakes are high. If the walls yielded to forces lower than their design specifications, the city will be on firmer moral and legal footing in asking Congress to pay for the all the property damaged and destroyed when the waters of Lake Pontchartrain poured into the city. If not, the government can say the cost should be borne by flood insurance and homeowners.
Much more at the link.
A termite expert is questioning whether tiny, voracious Formosan termites played a role in the failure of levee walls in New Orleans during Hurricane Katrina.
Louisiana State University entomologist Gregg Henderson said there are clear signs that the destructive insects were present, and he wants the opportunity to dig into the levees beneath the walls to find out if termite nests contributed to their weakening.
Army Corps of Engineers officials, however, say no evidence has been found to indicate that termites undermined the integrity of the levees.
Henderson, a world-renowned expert on termites, found evidence of insects -- both Formosan termites and fire ants -- in the joints between wall panels on both the London Avenue and 17th Street canals. Fire ants, an enemy of termites, tend to invade the channels created by the wood-destroying insects...
At the London Avenue Canal, where several engineering teams believe the pressure of water in the canal undermined a weak layer of sand beneath levee walls and caused them to slide and fail, Henderson found insects in 73 percent of the joints, he said...
...Jerry Colletti, corps manager for completed public works, said engineers determined that the pinholes created by termites in the plastic joint spacers and in some cases in concrete were not dangerous...
..."The corps did an evaluation to determine how much water would come through those little pinholes," he said. "The decision was made not to take any action on the joints. We looked into sealing the joints, and it was going to be expensive and we didn't see a purpose to it; the pinholes didn't cause a structural integrity problem."
"We don't have anybody at the corps who's a termite expert," he said...
The Army Corps of Engineers did a design review of the New Orleans levees in 1990. Apparently the engineers on the project thought the soil under the 17th Street Canal was stronger than it was, and one of their offices discovered this at that time:
Corps documents show the mistake of overly optimistic levee strength was detected by its Vicksburg, Miss., office, which directed local engineers to make changes. But when the chief engineer in New Orleans replied that the results were based on "engineering judgment," his superiors dropped the issue.
[Robert Bea, a University of California-Berkeley professor] said the discussion in the 16-year-old "design memo" points to the key decision that created fatal problems on the 17th Street Canal levee and could reveal a systemic problem that will show up during investigation into the London Avenue and Industrial Canal levees, which also breached during the Aug. 29 storm.
Was the floodwall failure at the 17th Street Canal due to bad design by the Army Corps of Engineers, or bad construction by contractors?
They pulled eight sections of the steel sheets that were driven into the ground, and so far that seems to indicate that they were installed to the designated depth: "Engineers Reverse New Orleans Levee Finding".
...The steel had been sunk into the ground to prevent water from saturating the soil and destabilizing the flood walls. Initial testing by sonar had indicated the sheet pilings were driven to only about 10 feet below sea level, even though the design called for 17.5 feet below sea level...
...Brig. Gen. Robert Crear said the length of the sections pulled all exceeded 23 feet. About six feet of the sheet piling was above sea level, leaving a little more than 17 feet below sea level - in accordance with design specifications.
Engineers also plan to test the concrete and the reinforcing bars in the flood wall to ensure they were made properly.
Also, engineers must try to figure out why the sonar tests yielded bad results on how deep the sheet pilings were driven.
NOLA has a round-up of the latest evidence pointing to the flooding being caused not by the hurricane so much as "operator error": incorrect design decisions by the Army Corps of Engineers and others. Commentary here. Keep us informed if we ever learn who's right.
When the New Orleans Sewerage and Water Board developed a plan in 1981 to improve street drainage by dredging the 17th Street canal to increase capacity for Pump Station No.Ã‚Â¤6, residents across the city applauded. Increasingly heavy rains were not only flooding streets, but pushing water into homes. Action was needed. It seemed like a no-brainer.
Today forensic engineers investigating the levee breach that flooded much of city during Hurricane Katrina aren't so sure. The search for the cause of the failure keeps returning to that dredging project as the probable starting point for a series of mistakes they believe ultimately led to the breach...
Before the project, the canal formed a roughly symmetrical "U" shape common to most canals. In the sections that would later fail during Hurricane Katrina, its average depth was about 12 feet below sea level and, at normal water levels, the Orleans side had about a 20-foot buffer of mud between the water and what was then a bare steel flood wall. That wall of sheet piling ran through the center of the levee to a depth 9.8 feet below sea level.
After the dredging, the bottom was 18.5 feet below sea level, and the canal-side levee had been shaved so narrow, water now touched the wall on the Orleans side. The "U" was now lop-sided and the water in the canal had shorter paths to the outside of the levee.
A review of records maintained by the two levee districts hasn't yet revealed why more extensive dredging was done on the Orleans side of the canal than on the Jefferson side.
"I've never seen a canal profile unbalanced like that, and I can't account for why it was done that way," said Bob Bea, a University of California-Berkeley professor and member of the Science Foundation team...
Monday 8/29, early morning: hurricane strikes
Monday 8/29, later that morning: Fox might have broadcast news of the break(s)
Monday 8/29, early afternoon: breaches reported to NO authorities 
Monday 8/29, 6pm : confirmed in a summary distributed by the Louisiana Office of Homeland Security and Emergency Preparedness 
Monday 8/29, "later in the day" : Blanco finds out 
Tuesday 8/30, midnight to 1am: CNN broadcasts a live report on the breach(s) 
Tuesday 8/30, late morning: DHS head Michael Chertoff finds out about the issue 
: two blog reports: here and here
: "News of levee breach hit D.C. late":
Federal and state emergency officials knew by early evening on the day that Hurricane Katrina made landfall that New Orleans' levees had ruptured and that much of the city was inundated with water, documents turned over to congressional investigators by Gov. Kathleen Blanco's administration show.
But that critical information did not make it up the chain of command to the U.S. Department of Homeland Security until more than 15 hours later, a delay that some Louisiana officials believe compromised the effort to rescue people stranded by floodwaters.
The breach of the 17th Street Canal levee, which was reported to New Orleans authorities early on the afternoon of Aug. 29, was confirmed by the Louisiana Office of Homeland Security and Emergency Preparedness in a 6 p.m. summary distributed to state and federal emergency officials in Baton Rouge.
"No power, 911 system down, EOC (emergency operations center) on emergency power and cell phones," the summary said. "Entire city flooded, except French Quarter/West Bank/Business district."
Farther down, in bold type, the summary report notes three breaches in the New Orleans area, including the 17th Street Canal...
FEMA Director Michael Brown, who was in Baton Rouge that day, would have had access to the summary, as did other state and federal officials.
Mark Smith, a spokesman for the state Office of Homeland Security and Emergency Preparedness, said it would have been clear to anyone who had read the summary what was happening in New Orleans. "Her (Blanco's) staff and our staff and the FEMA staff on site . . . all know the implications of any levee in Louisiana going down," Smith said.
But Homeland Security Secretary Michael Chertoff did not find out about the flooding until late Tuesday morning. Russ Knocke, a spokesman for Chertoff, said he doesn't know why the information wasn't conveyed sooner.
"I can't speak for Michael Brown. I can't tell you what happened with that information when . . . it was presented to Mike," Knocke said. "I can just tell you that from our part in Washington, D.C. . . . it was an extraordinarily frustrating period because we simply lacked visibility. That was a result of inadequate information from the field."
Knocke declined to speculate on whether the federal response would have been quicker had Chertoff understood the gravity of the situation sooner. "That's like asking someone to go back and play armchair quarterback," he said...
"Team Louisiana", the state-sponsored "forensic levee investigation team" with "six LSU professors and three independent engineers" says the floodwall on the 17th street canal was bound to fail due to improper design that didn't take into account weak soils below the levee.
And, they say that bad design should have been obvious to those responsible: the Army Corps of Engineers, Eustis Engineering (a local company) and Modjeski and Masters (national company).
That miscalculation was so obvious and fundamental, investigators said, they "could not fathom" how the design team of engineers from the corps, could have missed what is being termed the costliest engineering mistake in American history.
..."It's simply beyond me," said Billy Prochaska, a consulting engineer in the forensic group known as . "This wasn't a complicated problem. This is something the corps, Eustis, and Modjeski and Masters do all the time. Yet everyone missed it -- everyone from the local offices all the way up to Washington."
Reaction here and here.
Previously: "Floodwalls in Swampy New Orleans 'Like Putting Bricks on Jell-O'"
...the U.S. Army Corps of Engineers, said yesterday that its official timeline had discounted eyewitness reports by its top official in New Orleans, Col. Richard Wagenaar, confirming a levee breach Monday night. Instead, the Corps said the break was confirmed at 8 a.m. Tuesday.
"We probably had some calls over the period of the night, 'Hey, this might be going on,' " said Lauren Solis, spokeswoman for the Corps task force working in New Orleans, "but with the storm and everything else, we [the Corps's district engineers] went out the first we possibly could, which was daybreak Aug. 30 . . . and confirmed with our own eyes."
According to Bush Adviser Acknowledges Lack of Preparation for Katrina, on the night of Monday August 29, Marty Bahamonde reported to Michael Brown that "he had observed a massive break on the Lake Pontchartrain levee [the 17th Avenue Canal levee] and flooding over 80 percent of the city". Brown told Bahamonde that he would call the White House, but Chertoff denies that Brown told him that.
"The tenor of his discussions on Monday . . . was, this was bad, but it could have been worse," Chertoff said in an interview, adding that he learned of Bahamonde's report only after meeting him personally days later. "There was not a report to me until the following morning that there was a significant breach of the 17th Street levee."