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Hurricane Protection System in New Orleans 'A System in Name Only'

17.12.2008
The Army Corps of Engineers is mandated to provide New Orleans with an improved hurricane protection system by 2011. Virginia Tech geotechnical engineers are among the researchers analyzing the floodwall and levee systems, working with engineers from the U. S. Army Engineering Research and Development Center and from other universities. Advanced testing in Virginia Tech's geotechnical laboratory will determine the tests' cost effectiveness when applied to levee projects that entail hundreds of miles.

The failure of the New Orleans' levees after Hurricane Katrina struck the coastal city in 2005 is now labeled "the worst engineering disaster of the United States" by a professional organization that knows –– the American Society of Civil Engineers (ASCE).

The U.S. Army Corps of Engineers had complete authority for the design and construction of flood protection in the area around New Orleans, following the Flood Control Act of 1965. Today, it has until 2011 to provide New Orleans with an improved hurricane protection system.

This time, the corps is starting from a position that acknowledges the previous work was a “system in name only.”

Some 10 months after Hurricane Katrina’s devastation, the corps issued its June 1, 2006, follow-up study of the hurricane protection system for New Orleans and Southeast Louisiana. Among its findings, it said: “The System did not perform as a system: the hurricane protection in New Orleans and Southeast Louisiana was a system in name only ... The system’s performance was compromised by the incompleteness of the system, the inconsistency in levels of protection, and the lack of redundancy. Incomplete sections of the system resulted in sections with lower protective elevations or transitions between types and levels of protection that were weak spots.”

The report went on to criticize the inconsistent levels in the quality of materials used in levees, differences in the conservativeness of floodwall designs, and variations in structure protective elevations due to subsidence and construction below the design intent due to error in interpretation of information.

A number of outside private and government consultants and experts had already been called upon, and now the corps needed more help. Among the consultants were members of the Virginia Tech Geotechnical Program area of the Via Department of Civil and Environmental Engineering in Virginia Tech’s College of Engineering. The geotechnical faculty includes two National Academy of Engineering members, James Mitchell and J. Michael Duncan, known for their life-long contributions to this field.

Adding to the program area’s capabilities is the group’s W. C. English Geotechnical Research Laboratory. “This lab rivals those found at other top geotechnical educational programs such as University of California at Berkeley, the University of Illinois and the University of Texas,” said Ray Martin, civil and environmental engineering alumnus and geotechnical engineer. In fact, during the last Accreditation Board for Engineering and Technology (ABET) visit to Virginia Tech, evaluator Steven Wright of the University of Texas at Austin stated it was the best geotechnical university laboratory in the country, according to Martin. He adds, “There is probably not a better private lab either.”

Tom Brandon, associate professor of civil and environmental engineering at Virginia Tech, directs this laboratory, dedicated in 2003, and facilitated much of the Virginia Tech research associated with the failures of the New Orleans levees.

Martin, the former CEO of Schnabel Engineering, an international geotechnical engineering company, says his former company “frequently employed the services of Dr. Brandon and the English Lab when it had concerns about procedures or had questions about analyzing material. We were always very pleased. Dr. Brandon and Mike Duncan are two of the most knowledgeable researchers with respect to shear strength (investigations).”

Brandon’s work on the failure of the levees after Katrina garnered him the 2007 Commanders Award for Public Service. This award was specific to a project he completed for the Interagency Performance Evaluation Task (IPET) Force. Brandon and Duncan were on the IPET Floodwall and Levee Performance Evaluation Team to investigate the reasons for the failures that caused the breaches in the flood protection system in New Orleans.

Brandon and Duncan analyzed seven breaches in the floodwall and levee system, working with engineers from the U. S. Army Engineering Research and Development Center in Vicksburg, Miss., and engineers from other universities. Their work continues to provide design guidance to the New Orleans District of the Corps of Engineers concerning methods of evaluating the stability of remaining floodwalls and levees in the area.

They had two papers related to their IPET work in a special issue on Hurricane Katrina published by the ASCE Journal of Geotechnical and Geoenvironmental Engineering.

Brandon was also a member of the technical team that conducted the London Avenue Canal Load test last summer. At this canal, just down from the 17th Street Canal, in New Orleans, two breaches occurred on the morning of Aug. 29, 2005. The breaches resulted in the formation of a gap between the wall and the levee on the canal side of the wall. Water then flowed down through the gaps into the underlying sand. High water pressures in the sand uplifted the marsh layer on the landside of the levee, resulting in concentrated flow and erosion, removing material, and reducing support for the floodwall, which failed catastrophically, according to the Army Corps of Engineers’ evaluation.

Brandon and Duncan have submitted a proposal to analyze the data collected from the London test with the intent of integrating the findings into current design methods.

Brandon is also the only non-corps member of the Mississippi Valley Division Geotechnical Quality Assurance Team. This team oversees the quality assurance efforts on New Orleans area flood protection construction and reconstruction efforts. It reviews site exploration plans, inspects drilling efforts to obtain samples, tracks the samples through the laboratory testing efforts, and reviews the final data. It also investigates the use of the laboratory and field data in obtaining design strength parameters.

The team has written a manual, revised seven times to date, called Guidelines for Geotechnical Exploration and Testing, which is being used in present and future projects.

Brandon’s knowledge of the New Orleans area has secured him a number of independent technical reviews (ITRs) on different projects related to levee and floodwall design. “I mainly review the technical design reports submitted by contractors for correctness and provide comments,” Brandon says. He is currently looking at the data produced by a complex geotechnical computer model that questioned the viability of lake levees in the East Jefferson and St. Charles parish of New Orleans.

Since the Army Corps of Engineers is mandated to provide New Orleans with an improved hurricane protection system in three years, it cannot afford to ignore new findings. However, as it enters into contracts that include overly conservative designs, it may rely on future research performed by engineers such as Brandon to modify the needs, possibly reducing costs.

For example, Brandon and some graduate students are reviewing the current specifications of organic content of fill materials, a joint project between Virginia Tech and the Savannah District of the corps of engineers.

“The Corps needs about 100 million cubic yards of soil for new levee construction. Currently, they have located about 30 million cubic yards of local soil that meets their current specification of nine percent or less organic content. If they could modify their specification to allow soils with a greater organic content, then more local fill material would be available for construction. If they have to import soils from afar, then the cost increases dramatically,” Brandon explains.

His research project is to assess the engineering consequences of allowing a higher organic content. To do so, two Virginia Tech geotechnical engineering students went to New Orleans and obtained about 2,000 pounds of different soil samples that have organic contents greater than nine percent.

These soils will be tested, and the effects of using these soils in levee construction will be examined. “If we can justify the use of higher organic contents, then more local soils can be used for levee construction, and the cost of construction will be greatly reduced,” Brandon says.

The cost factor is driving another research project headed by Brandon. “After Katrina, many geopundits criticized the corps’ design and testing methods. They felt the corps should have been using more advanced types of geotechnical tests. While the advanced testing methods may be good for relatively small projects, the cost effectiveness of these tests may be questioned when applied to levee projects that entail hundreds of miles, and soil borings are located only every 500 to 1,000 feet,” Brandon adds.

Consequently, he will direct very advanced tests in the English Geotechnical Lab, and the results of his complicated tests will be compared to the simpler tests conducted in area labs to determine if the additional expenses do actually result in safer structures.

Lynn Nystrom | Newswise Science News
Further information:
http://www.vt.edu

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