Higher-ups raised red flag, then dropped it Friday, December 30, 2005 By Bob MarshallStaff writer
The engineering mistakes that led to the canal levee failures that flooded most of New Orleans during Hurricane Katrina were found and then dismissed in the Army Corps of Engineers' design review process in 1990, an investigative team reviewing the failures says.
Documents, obtained by The Times-Picayune and provided to forensic engineers studying the levee breaches, show project engineers made a critical mistake in assessing soil strengths on the 17th Avenue Canal project, said Robert Bea, a University of California-Berkeley professor who is a member of the National Science Foundation team.
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 (Army Corps of Engineers'?) chief engineer in New Orleans replied that the results were based on "engineering judgment," his superiors dropped the issue.
Bea 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.
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That's interesting but you know what? I am quite skeptical. First of all, they are using the word "levees" at some places when they clearly meant "floodwalls". Secondly, the design was for a category 3 hurricane, at a time when the wetlands and barrier islands surrounding and protecting New Orleans, were far less eroded. Those wetlands absorb any hurricane's power and protect the city. They had been lost by poor management long before the storm hit, a storm that was a category 4 and beyond the design criteria anyway. Thirdly, the floodwalls failed after they had been overtopped. The storm surge in Lake Ponchartrain was above the level of the lowest floodwalls, and no floodwall was ever designed that could withstand the erosion of its foundations that happens per necessity when flood waters pour over the top. Levees are far more tolerant of being overtopped than floodwalls, but they take up much more real estate and are concomitantly far more expensive, so that wasn't an option because nobody would spend the money.
We knew perfectly well, and in plenty of time, what it would have taken to protect New Orleans from a storm like Katrina. It would have cost $14 billion, and nobody was willing to spend the money. That's the end of the story. Trying to blame some engineering firm for this tragedy is just a colossal boondoggle, and heinously unethical, to boot.
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The same thing happened after 9/11, when some people wanted to blame the buildings' designer for the collapse. You know what? It's impossible to design an indestructible building, and nobody would pay for it if you did. It would be far too expensive to build. The buildings were designed beautifully, and held up amazingly well, even when smashed into by airplanes far bigger than they were designed to withstand. Many many buildings would have fallen OVER from the impact alone, taking out everyone inside as well as many people for blocks around. The two World Trade Center towers not only withstood the impact, but also withstood a hotter fire than any building could be expected to have, one from the combustion of all those tons of jet fuel, for half an hour, allowing a whole lot of people to evacuate.
Yet the designer was raked over the coals about it, adding to his private anguish and worry that there was anything he possibly could have done that would have saved one more life. Instead I think he should have been greatly commended.
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See, what customers do, is they come to you and say "design me a building, wall, machine, bridge, that can do x, oh and make sure it can withstand y and z as well". So you go back to them and say, "Okay, for x y and z we will need this much room and it will cost so many dollars". The customer then says "noway! We can't let you have but half that room and 1/3 that much money." So then you go back to them and say, "with 1/2 the room and 1/3 the money you can still do x, but it won't withstand y and z, only v and w."
So then they say "good, build it that way". And you do. Then if they subject it to 2y and 3z and it fails, they want it to be your fault.
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quote:Originally posted by Tatiana: That's interesting but you know what? I am quite skeptical. First of all, they are using the word "levees" at some places when they clearly meant "floodwalls".
Actually that's an incorrect assumption. The floodwalls they are talking about were levees reinforced and topped by metal floodwalls. It's an easy assumption to make - that they were floodwalls only - since the talk has centered on 'floodwalls' failing. BUT the floodwall actually topped/was part of the levee, so it was both. I drove over the 17th Avenue Canal bridge regularly when I lived and worked in that area of New Orleans, so I know what I am talking about.
quote:Secondly, the design was for a category 3 hurricane, at a time when the wetlands and barrier islands surrounding and protecting New Orleans, were far less eroded. Those wetlands absorb any hurricane's power and protect the city. They had been lost by poor management long before the storm hit, a storm that was a category 4 and beyond the design criteria anyway. Thirdly, the floodwalls failed after they had been overtopped. The storm surge in Lake Ponchartrain was above the level of the lowest floodwalls, and no floodwall was ever designed that could withstand the erosion of its foundations that happens per necessity when flood waters pour over the top. Levees are far more tolerant of being overtopped than floodwalls, but they take up much more real estate and are concomitantly far more expensive, so that wasn't an option because nobody would spend the money.
Again, a mistake. You may have missed the announcement this week that the National Hurricane Center has adjusted the strength of Katrina when it hit New Orleans. Katrina was actually a strong Category 3 when it reached New Orleans, not a Category 4 or 5. Friends there have told me that they had gusts of 125 mph, but the sustained winds were a high Category 3. That means that the Category 3 design presumably would have been able to withstand the storm.
Also, the 17th St. Levee failure (Metairie and the Lakefront) was not because of being overtopped. The soil of the water soaked levees actually shifted laterally, moving the floodwalls and causing the breach. It was a failure of the levee, because the weak soil was not properly factored into the design. I posted a link to that information in another New Orleans thread here last month. The other article mentioned that a proposed design for a floodwall depth of 35 feet for the metal floodwall was overruled and the floodwall was instead done at 17.5 feet. Some of that is also mentioned in the complete article, linked above.
The Levees which failed in the Ninth Ward, St. Bernard Parish and Plaquemines Parish were overtopped by the storm surge. They were actual levees without a reinforcing metal floodwall. The reason they probably failed was "Mr. Go" a straight deep water canal that the Corps dug to facilitate deep draft cargo ships entering the Port of New Orleans. The storm surge traveled up that straight deep channel, and was undiminished because of the straight deep design.
All of those levees along that canal were overtopped. In theory the flooding MIGHT have stopped there, had the 17th Street levees not shifted, since the water in that canal did not overtop the levee/floodwall.
quote:We knew perfectly well, and in plenty of time, what it would have taken to protect New Orleans from a storm like Katrina. It would have cost $14 billion, and nobody was willing to spend the money. That's the end of the story. Trying to blame some engineering firm for this tragedy is just a colossal boondoggle, and heinously unethical, to boot.
The Corps is being blamed, not an engineering firm. The subcontractors followed the Corps' design to the letter, and actually exceeded the depth required by them.
I agree that the Wetland restoration would have saved the city. It was certainly a much cheaper alternative - both emotionally and materially - to what happened. Hindsight.
I think that, like so many other environment programs, the Wetlands Project got scrapped because of the subtle and not so subtle anti-environmentalist thinking of the current Administration. IMHO our government and business leaders have to stop thinking of short term profits and start planning for our long term future, or there won't be much left to save.
quote: The Corps is being blamed, not an engineering firm. The subcontractors followed the Corps' design to the letter, and actually exceeded the depth required by them.
As I understand it, it wasn't the Corps design. Eustis Engineering designed it and the design was checked by the Corps. Bridges in Florida are designed the same way. Florida DOT rarely does the engineering design, but hires private engineering firms to do the work. FDOT then checks the work to make sure it meets there standards.
Geotechnical engineering involves a lot of unknowns which is why you always use conservative numbers in your strength estimates. Soil is not like steel or even concrete. I know the unit weight of steel is about 492 pcf and concrete is about 150 pcf. If I know the mix design of the concrete and know it was mixed properly, I can tell you with fair accuracy what it's strength will be. With soil, you can only make an educated guess about what the unit weight, friction angle, cohesion, modulus of elasticity, etc. is. Even running expensive tests only gets you so far because that in no way guarantees that the soil 5 feet away is the same.
I'm not sure why they would have used average values, though. It's easy enough to run analyses for sheet piles modeling both the strong layers and the weak layers. The same goes for slope stability. It could be a case where the reporter just didn't understand what they were saying and didn't quite get the right message across.
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From what I've read... The levee-building and the addition of the floodwalls were separate projects. The company which laid in the floodwall on the section that failed had fired off formal letters telling the Corps of Engineers that the company's tests indicated that the levee had not been sufficiently compacted. The Corps of Engineers sent back a reply insisting that the Corps' own testing confirmed that the levee compaction exceeded specs and that the company fulfill its contractual obligations on that basis. At which point, the company complied, but on its own initiative and at its own cost drove in pilings to depths which exceeded their contract.
quote:Originally posted by aspectre: From what I've read... The levee-building and the addition of the floodwalls were separate projects. The company which laid in the floodwall on the section that failed had fired off formal letters telling the Corps of Engineers that the company's tests indicated that the levee had not been sufficiently compacted. The Corps of Engineers sent back a reply insisting that the Corps' own testing confirmed that the levee compaction exceeded specs and that the company fulfill its contractual obligations on that basis. At which point, the company complied, but on its own initiative and at its own cost drove in pilings to depths which exceeded their contract.
Yes you are right. As I said I lived there during that time period and I remember the construction. Adding muscle to the existing Levees was typical and usual. I'd like to add that I agree that it was a poor choice. The company who did the work kept the records showing that they exceeded the specifications, and when the pilings were dug up those records were corroborated. They make their misgivings known, and when they were told to do it to only 17.5 feet they covered their derrieres by keeping a record of what they were told and what they did.
quote:Originally posted by zgator: As I understand it, it wasn't the Corps design. Eustis Engineering designed it and the design was checked by the Corps. Bridges in Florida are designed the same way. Florida DOT rarely does the engineering design, but hires private engineering firms to do the work. FDOT then checks the work to make sure it meets there standards.
While the designs and construction were done locally - you are right btw - the Corps has taken responsibility. They approved the designs and they have said that fact makes them responsible. I find that refreshing in a government organization. I wish there was more of that!
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quote:Originally posted by zgator: It's the same with FDOT. If something fails, they still have ownership and take responsibility.
aspectre, do you have a link to that? I haven't seen that one.
Thanks for that info, zgator. I learned a lot about civil engineering procedure in the discussion on the previous New Orleans thread here.
I'd be interested in reading that too aspectre, if you have it. I have been following this closely, since I really care about my old home town's problems and reconstruction.
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I've done more searching of New Orleans news sources to find out more about the Levee failures. I didn't find the exact source for aspectre's info, but here are some interesting exerpts:
quote:Louisiana State University computer models have indicated that the levee and flood wall, even if built as designed, would fail if the water in the canal rose to nearly 12 feet above sea level, as water marks on the flood wall indicated it had during Katrina. That was in part because the bottom of the canal was a foot lower than the bottom of the sheet piling, meaning water would be able to seep from the canal to the dry side of the levee, loosening the soil enough to cause the levee to slide and undermine the flood wall. http://www.wwltv.com/local/stories/wwl121305floodwall.64b852b.html
quote:weak soils beneath levee walls along the 17th Street and London Avenue canals likely contributed to wall failures there, while the levee wall along the Industrial Canal may have been topped by storm surge in several locations, leading to its failure. Levees in St. Bernard Parish may have been rapidly eroded by surge in part by the use of sand in their construction, that report said, and levees elsewhere were simply overwhelmed by storm surge. The report also was critical of the design of connections between various hurricane protection structures, including levees, walls and gates. Final report due in fall A preliminary report from the Interagency Performance Evaluation Task Force agreed with most of the findings of the joint ASCE-NSF report. The task force is expected to issue additional reports as the corps and contractors rebuild the area's levee system. Its report on the structural performance of the hurricane protection system is due on May 1, with a final report due on June 1. Final report due in fall In approving construction of existing hurricane protection projects, Congress authorized specific levels of protection that the corps has said is the equivalent of protecting the area from a fast-moving Category 3 hurricane. Congress recently approved spending $8 million to study ways of protecting south Louisiana from hurricanes as strong as Category 5. The committee review of the task force's work will include a look at the modeling of the area's interior drainage system, which includes the New Orleans canals; modeling of Katrina's surge and waves and an analysis of floodwall and levee performance. http://www.nola.com/search/index.ssf?/base/library-92/113535174694511.xml?nola
quote:What's in the (new) levee plan
03:21 PM CST on Thursday, December 15, 2005 WWLTV.com Congressional Plan for levee repair and improvement
Phase 1
To be completed by June 1, 2006 – cost $1.6 billion - repair breaches - correct design and construction flaws - bring heights back to Pre-Katrina levels
Phase 2
To take up to two years – cost $1.5 billion - armor levees (cover them and support them) with concrete and stone - Close the 17th Street, London Avenue and Orleans Avenue canals - Place gates at Lake Pontchartrain - Provide state-of-the-art pumping stations at those gates.
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This article on MSNBC reports on the content of a lawsuit by Pittman Construction regarding the weak soil. Pittman Construction is no longer in business.
quote:...the 1998 documents — filed as part of a legal dispute over costs — indicate the contractor complained about “weakness” of the soil and “the lack of structural integrity of the existing sheet pile around which the concrete was poured.” The ruling also referenced the “flimsiness” of the sheet piling.
The construction company said as a result of these problems the walls were shifting and “out of tolerance,” meaning they did not meet some design specifications. Nevertheless, the Army Corps of Engineers accepted the work. “It seems to me that the authorities really should have questioned whether these walls were safe,” says van Heerden.
So the implication is that soil tests were part of this lawsuit, and that once Pittman construction got into the job, they realized the potential disaster they were dealing with. The corps refused to address the problems the construction company had discovered, and insisted on the contractor following the plans as specified.
quote:Army engineers: Levee warnings unreported NEW ORLEANS (AP) — Engineers responsible for monitoring the levees that failed following Hurricane Katrina were never told that canal water had been pooling in yards beside a flood wall months before the storm, an Army Corps of Engineers manager said Friday. Residents living along the 17th Street Canal told The Times-Picayune newspaper in an article published Friday that they had complained to the city Sewerage and Water Board nearly a year ago about water pooling in their yards. City workers came out and concluded environmental testing was needed to determine if water was seeping through the levee, said Beth LeBlanc, whose home is about 100 yards from where the levee later failed. But no one, including the Sewerage and Water Board, informed the Corps of Engineers or the Orleans Levee District, said Jerry Colletti, the Corps' operations manager for completed works in the New Orleans District.
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