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Tom Sawyer/ENR
London Avenue Canal floodwalls showed significant distress from Katrina, even in areas that did not fail.

The storm in Southeast Louisiana over the quality of its engineered flood defenses when Hurricane Katrina swept ashore on Aug. 29, 2005, is about to turn from a technical analysis of the structures and their construction, to a dissection of the political, financial and design decisions that lay behind it having been built the way it was in the first place.

A task force convened at the direction of Lt. Gen. Carl A. Strock, commander of the U.S. Army Corps of Engineers, to sort out the decision chronology behind the development of the system, has completed its work. The task force’s report is almost ready to turn over to the Dept. of Justice for final review, a Corps source reports.

“The most significant comprehensive reviews have already taken place,” says Corps spokesman Gene Pawlik. He says the report is just being double-checked to ensure “no significant documents of record” have been missed before the expected public release, although he adds that he could not yet say when that release date will be.

The Hurricane Protection Decision Chronology Report—which some have nicknamed “The Blame Report”—promises to be a valuable, if cautionary tale for current and future generations of Corps planners and decision makers, elected officials, as well as for the newly consolidated levee boards in New Orleans. All are fighting to raise the caliber of oversight of proposals for new work put forth by the Corps.

An April 19 New Orleans presentation to the Southeast Louisiana Flood Protection Authority-East included references to a good example of how a decision path taken, and others not taken, had enormous ramifications 20 years down the road.

The Corps was seeking right-of-access permission so it could conduct a load-test on a section of levee I-wall in Orleans Parish. Lt. Colonel Murray Starkel, deputy commander of the New Orleans District, made a point of calling attention to a load-test the Corps did on a floodwall mockup in the Atchafalaya Basin in 1985.

Related Links:

The Interagency Performance Evaluation Taskforce website has hundreds of pertinent documents related to the design and construction of the Southeast Louisiana Flood Protection System.

Two papers that built upon the E-99 study can be found at The Electronic Journal of Geotechnical Engineering:

Soil-Structure Interaction Effects in Floodwalls,” by Mete Oner, William P. Dawkins, professors, School of Civil Engineering, Oklahoma State University, Stillwater, Okla.; Reed Mosher, research civil engineer, U.S. Army Corps of Engineers, Waterways Experiment Station, Vicksburg, Miss., and Issam Hallal, structural engineer, Ralph M. Parsons Co., Pasadena, Calif.

Shear Ring Method for Soil-Structure Interaction Analysis in Floodwalls,” by Mete Oner and William P. Dawkins, School of Civil Engineering, Oklahoma State University, Stillwater, Okla. and Reed Mosher, research civil engineer, U.S. Army Corps of Engineers, Information Technology Laboratory, Waterways Experiment Station, Vicksburg, Miss

Levee Board Gives Corps Conditional Permission for Levee Load Test

The report on that test, the E-99 Report, (2.35 MB) has been discussed in Congressional hearings and noted in the report produced by the Interagency Performance Evaluation Taskforce that analyzed the behavior of the New Orleans flood defenses during Hurricane Katrina. It has been cited as an example of a Corps of Engineers failure to perceive the significance of a phenomenon observed in that test, which turned out to be the trigger to the failure of some of the floodwalls during Hurricane Katrina 20 years later.

The E-99 Report has also been posted, with hundreds of other technical documents relating to the design and construction of the Southeast Louisiana flood defenses, on the IPET website since late 2005. Two subsequent studies that built upon E-99 Report observations are also linked here.

The 1985 test was designed to determine whether the calculated safe water elevation of a sheet-pile-supported concrete floodwall was valid. Within the limits of the design of the inquiry, the calculation was validated.

What the test did not do, however, was make the connection between a phenomenon observed, which was the opening of a tension crack down the wet side of the sheet pile wall, and a potential failure mode that has since been identified as the cause of some of the catastrophic levee blowouts during Hurricane Katrina. One of the limitations of the 1985 load test was that it was not an accurate model of the canal levees and I-walls of New Orleans. Rather than build the sheet-pile test wall into the top center of the earthen levee, the Corps built the wall on the landside toe. That may have demonstrated that the sheet pile and concrete wall could withstand the design water load, but it did not represent the soil interaction. This proved to be a fatal flaw.

“Those tests did indicate rotation of sheets but, because that wasn’t the focus of the study, the Corps failed to bring those measurements to their design standards,” says Tom Jackson, president of the SLFPA-E. Prior to the intensive, post-Katrina study of flood wall performance, the behavior observed in the test was “not normal failure a designer creating I-walls would have looked at,” Jackson adds, “but when you go back to E-99, you have to wonder why they didn’t look at that.”