Talk:How the Army Corps of Engineers closed one New Orleans breach

Impressed with quality of article
I am very impressed with how well this article is written. It also has a NPOV flavor that this story could have meandered from very easily, which I give you a whole lot of credit, SEWilco. The article could have gone either a slam and critize the feds or a glowing PR piece for the Army Corp of Engineering. Good work. Digging up this sort of information is not easy, and I'm glad that this was given the distinction of being a featured article. I would like to see some more sources as well, but that is not easy for a piece like this, although some related articles might be useful. I'll see what I can add here myself in that regard. --Robert Horning 01:07, 10 September 2005 (UTC)
 * I want to add... more sources besides the Army. Still, they are the best original source you can get, but I'm sure other viewpoints can be found.  --Robert Horning 01:13, 10 September 2005 (UTC)

an update on some inaccuracies in the article
great article but i must point out a few things that are inaccurate about the numbers you present. You say that the storm surge was 20 feet in lake pontchartrain and that the levees are 17 feet so they were breached. in fact, buoys in the middle of the lake measured a maximum storm surge elevation of 8 feet according to scientists at the LSU hurricane center. the water levels along the shoreline of the lake at new orleans were higher due to the sustained north winds that pushed the water up against the levees and amplified the water levels along the n-s trending drainage canals at london ave and the 17th street. The levees along the lake are at (or supposed to be at) 17 ft. However the levee height along the drainage canals is only 11-12 feet. Still the water levels in these canals never reached an elevation high enough to top the levees here, instead what happed was that the levees at both the 17th street canal and the london ave canal were undermined due to inadequate design, engineering and construction. The shallow geology in the subsurface below new orleans is quite complex due to the meandering and channel switching of the mississippi river over the past 5000 years. Also there is an extensive, 30 foot thick barrier island sand deposit underlying the area in the vicinity of the london ave canal. In the area of the 17th street breach the underlying geology consists of a thick peat. Both the clean sand and the peat are pourous sediments that allowed the flow of water to occur underneath the levee. As water began to seep through, a pathway was established and the levees were pushed back horizontally and collapsed. In both canals sheet piling had been driven as part of the original design in order to prevent this type of seepage failure however it was not even driven to depths as deep as the canal bottom (10 feet at london ave and 17 feet at 17th street). But the mytery behind the greatest engineering failures of US history is the fact that the usace had the soil boring data and knew the soil properties before the levees were built, however they did not apply these findings to the design.