How important are these ignored objections to the rebuilding of the levees: using soil is not as good as using clay, and the old design was not good enough to be repeated?
It is my understanding that it was not the design of the levee that caused them to fail, but the poor construction and failure to follow plans that caused the levee breaks. Were the leees built according to specifications, they would have held under a Category 3 hurricane, which was what they were designed to do. However, a very strong Category 4 is what hit New Orleans. Had the levees held, there may have been some topping of the levees, but the big flood, which started the day after Katrina as a result of the levees being breached, would not have happened.
I cannot speak to the clay vs soil discussion. ************************************************* 02-19-06, 07:33 AM tsaeb I think that I meant the implementation of the old design, which is, I think, about what you wrote.
I got the objections from a TV program and may not remember them exactly.
02-19-06, 07:58 AM DorianGreyed The levees probably would have held had shortcuts not been taken in construction. Remember that only parts of a couple of levees failed. This is not to say that there haven't been improvements in design and construction in the last 4 decades, but, had those levees been built according to specs, there would have been a great deal less flooding in New Orleans and it would have come from overtopping the levee, and possibly from pump failure.
02-23-06, 04:32 AM tsaeb Lately, I have heard the objection that due to not enough money, the new levees are being built to withstand a Category 3 hurricane, not a Category 5 hurricane as Katrina.
02-23-06, 08:10 PM aminator2002 That is right they are rebuilding the levees to withstand Cat 3 again.
The soil in New Orleans is horrible to build on. The levees sink every year and therefore have to be constantly maintained. It has nothing to do with poor original construction. It does have to do with budget shortfalls and perhaps a lack of honesty in dealing with public safety.
DG... can you provide some back up for your comments?
02-23-06, 08:38 PM DorianGreyed It was on most major news reports that the levees were breached because the concrete suppoprting walls/rods/panels/whatever were not sunk to the level specified by the plans. As far as budget shortfalls, it was also shown that money earmarked for levee repair and maintenance was spent on other things, some totally unrelated to not only levees, but any official business. This was mentioned in several threads in AP about Katrina.
Levees, like buildings, always need maintenance and sometimes repair. The ones less than a mile from my house are always being worked on. They held during the 500 year flood in 93. But they were close to being overtopped, which is what the damage would have been limited to had the levees not failed in New Orleans. Overtopping from Katrina wouldn't have resulted in putting 80% of New Orleans underwater. Overtopping is like splashing water out of your bathtub - messy, but not a big deal. A breached levee is like a hole in your bathtub, except the breached area keeps gets bigger. Remember that the serious flooding started after Katrina had passed by. That is why Bush et al. thought that New Orleans was spared the bullet.
tsaeb, you are right that the latest information says that the levees are only being built to withstand a Category 3. If they are built and maintained proerly, they will prevent the kind of damage that Katrina from flooding wrought on New Orleans. If the flooding doesn't overwhelm the pumps (and if the pump operator doesn't skip town, like he did last time), there will be minimal flooding, according to the experts in New Orleans, the Army Corps of Engineers, and the hurricane experts in nearby universities. Most of the damage done in New Orleans by Katrina was preventable.
02-24-06, 09:40 AM aminator2002 Here is a good article that is prepared by engineers. Article about levee failures
quote: If the flooding doesn't overwhelm the pumps (and if the pump operator doesn't skip town, like he did last time), there will be minimal flooding, according to the experts in New Orleans, the Army Corps of Engineers, and the hurricane experts in nearby universities. Most of the damage done in New Orleans by Katrina was preventable.
I would like you to find a source that backs this up in print (and not just numerous major news sources)... I can't believe that the Army corp, experts in New Orleans or hurricane experts are saying this. Today I mean. Perhaps they may have said this before they had all the information they now have. Certainly none of the experts I've seen would back it.
02-24-06, 11:46 AM DorianGreyed "According to the Times-Picayune on June 18, 2004, Naomi said, "The system is in great shape, but the levees are sinking. Everything is sinking, and if we don't get the money fast enough to raise them, then we can't stay ahead of the settlement... The problem that we have isn't that the levee is low, but that the federal funds have dried up so that we can't raise them. " - Posted by, 9.8.05 (Bold mine - DG)
"Another note - it seems to me that the construction project that was in process at the time of the Hurricane, the one at the bridge where the major breach occurred, was not properly shored during construction. It seems to be an underfunded project and when working on systems like this "safety first". This should be part of the investigation so that construction standards can be set a bit higher if needed." - Same Post, (Bold mine - DG) -------- SHORT SHEETED Sonar shows 17th Street Canal leve sheetmetal pilings are seven feet shallower than the Corps claimed Thursday, November 10, 2005 By Bob Marshall Staff writer
Sheet piling supporting the failed floodwall on the 17th Street Canal extends just 10 feet below sea level, 7 feet shorter than the Corps of Engineers has maintained, a team of investigators said Wednesday, strengthening earlier findings that faulty design and construction played a role in the canal breaches that flooded much of New Orleans during Hurricane Katrina.
An LSU forensic engineering team, working in conjunction with the state attorney general's office, began examining the levee foundation with ground sonar Wednesday. The first reading was taken about 150 yards south of the break that allowed water from Lake Pontchartrain to inundate the city.
Independent engineers have questioned whether the pilings, even at the corps' stated depth, went down far enough to support the floodwalls and prevent storm surge from penetrating beneath the earthen levees and causing structural failure. - Times-Picayune -------- Apparently, I am not the only one who saw problems in the construction of the levees. Aminator's own post agrees with what I have said. Further in the Times-Picayune article, it states that, while the Corps of Engineers said the pilings were at one depth, their plans showed another, shorter depth. It is important to note that these shorter depths were at the point of failures of the levee. No doubt that soil conditions were also to blame. There was also a layer of peat found for quite a distance around the failures, and the pilings didn't go past that. There is also no doubt that the construction plans called for depths that are simply not deep enough. The current recommended depth for the pilings is 40-50', a figure arrived at in the early 1990s.
Also in the article - "Because the corps has refused to release final design drawings and other documents, researchers have been trying to solve what they call "the mystery of the sheet piles." But even with the sonar measurements, it still is unclear which government entity is responsible for the pilings."
This article is not one of the ones I saw that stated that the pilings were not up to specs, but it serves the purpose. Possibly the articles I saw were after this, after the Corps released the plans. What this article does make clear, however, is that both the design and the construction of the levees, especially at the failure points, were flawed. Remember that the levees held at almost all the other points, where the pilings have not been shown to be short. There is no one factor that caused the failure.
02-24-06, 11:50 AM DorianGreyed from Wikipedia - A report of statements made by the head of a team from the American Society of Civil Engineers, says that, when the geological borings were made in 1981 prior to the construction of the 17th St Canal, they revealed to both the Army Corps of Engineers officials and the contractors who designed and built the wall the nature of the weak layer of soft soil that would lie under the base of flood walls' foundation of steel piling.
"According to the analysis, they've got the soil strength test. It doesn't show exactly the input for the analysis, but assuming they used it and came out with factors of safety, it's showing the numbers are safe. So it leaves an open-ended question as to why the flood wall failed."
The original design for the steel sheet foundations for the flood walls showed a proposed depth of 10 feet, and the design documents show calculations were made with the wall base at 12.8 feet. According to a New Orleans engineer, the depth was apparently increased later, to 17-foot depth, and this is what was built. However, on November 10 an article in the Times Picayunne reported that investigations using sonar by a forensic engineering team from the Louisiana State University show that at one point near the 17th Street Canal breach the piling extends just 10 feet below sea level, 7 feet shorter than the Corps of Engineers had maintained.
"The corps keeps saying the piles were 17 feet, but their own drawings show them to be 10," van Heerden said. "This is the first time anyone has been able to get a firm fix on what's really down there. And, so far, it's just 10 feet. Not nearly deep enough."
According to Professor Robert Bea, a geotechnical engineer from the University of California, Berkeley, it is likely that the Katrina storm surge created unusual subterranean pressures under the walls. Those pressures appear to have made soil under the sheet pile weaker so that it gave way, moving the steel sheet-pile-and-concrete walls along with it. But engineers studying the levees also say that other, unknown factors, including structural problems in the walls, could also have contributed to the breaches.
Prof. Bea has said that the design firm, New Orleans-based Modjeski and Masters, could have followed correct procedures in calculating the safety factors for the flood walls. But he added that design procedures of the Army Corps may not account for changes in soil strength caused by the changes in water flow and pressure during a hurricane flood.
The size of the design safety margins has also been questioned by Prof. Bea. He said the Corps had applied a 30% margin over the maximum design load. A more typical margin used for highway bridges, dams, off-shore oil platforms and other public structures would be a doubling of strength. There were also indications that sub standard concrete may have been used at the 17th Street Canal.
02-24-06, 12:18 PM aminator2002 One of the articles I posted supports that the design of the 17th street levee was a mistake. The depth was designed to be too low for what engineers know of soil bearing capacities. This was really clearly pinned on a design calculation problem.
There also is a detailed report of the construction going on at the bridge project. Improperly shored (against a hurricane LMAO)is not exactly what the study found but good enough, let's agree on that. Construction projects should apparently not be allowed during hurricane season, but it seems all reality goes against that considering how much work the Corps (currently does all the work from what I understand) can accomplish... they are slow.
It seems to me though that almost all agree that overall the system is very very vulnerable and that these instances of serious breaches were something to be expected along the course of the system. Many studies point out that the interconnections, the overlap of responsibility and the inconsistency of height are potential problems. But more than anything I don't hear anyone saying that it's very sustainable for the future as you seem to be saying. It will all get worse as the city sinks and as sea level rises. I think before everyone goes hustling back to their homes that some serious thinking about the real cost needs to be taken into account.
02-26-06, 04:51 AM tsaeb I saw a program about how the tsunami managed to cause the damage which it caused. I heard that the waves did not enter the coasts as one might imagine; instead, the waves became high and in the shape of a "C" due to the great amount of debris which they picked up along the way.
Perhaps, to a smaller degree, some characteristic of the waves, which could not ever have been foreseen, caused in part the levees to breach. I do not know how far along or how deep down go hurricane waves while traveling, but maybe the wind was yet another factor.
I think that the exponentially increasing strength of hurricanes, unforeseen by most, also hinders trying to prepare technologically for them.
This message has been edited. Last edited by: DorianGreyed,
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