NBC: “Damning Evidence” - New Orleans Levees

NBC: “Damning Evidence”
September 29th, 2005

NBC Nightly News is reporting “Damning Evidence,” New Orleans levee was reported weak in 1990s and record show, “construction firm alerted engineers, but no action was taken.”

NBC News has obtained what may be a key clue, hidden in long forgotten legal documents. They reveal that when the floodwall on the 17th Street Canal was built a decade ago, there were major construction problems — problems brought to the attention of the U.S. Army Corps of Engineers.

http://blog.thedemocraticdaily.com/?p=721

http://www.stormingmedia.us/34/3418/A341804.html


Performance of Levee Underseepage Controls: A Critical Review
Authors: Thomas F. Wolff; ENGINEER RESEARCH AND DEVELOPMENT CENTER VICKSBURG MS GEOTECHNICAL AND STRUCTURES LAB

Abstract: The Federal Government through the U.S. Army Corps of Engineers (USACE) has a large investment in flood-control levees. Where such levees are built on pervious foundations, seepage beneath the levee (underseepage) during floods can produce pressure and flow conditions capable of initiating subsurface erosion leading to levee failure. Two adverse phenomena may occur; one is sand boils which involves the movement of subsurface sand to the surface by flowing water, and the other is heaving which involves the upward movement of a relatively impervious surface layer resulting from subsurface water pressures in excess of its weight. To prevent such occurrences, the USACE has developed a set of procedures to analyze underseepage conditions on a site-specific basis and a set of procedures to design underseepage control measures. For the most part, these procedures were developed in the 194Os and 1950s. Intensive construction of control measures was accomplished in the 195Os and l96Os. Several moderately large and major floods have provided data from which the validity of the procedures and the security of the constructed system can be inferred. Also, since the 195Os many technical advancements have been made in engineering analysis techniques and construction methods that may merit application to underseepage problems.The Federal Government through the U.S. Army Corps of Engineers (USACE) has a large investment in flood-control levees.

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