.comment-link {margin-left:.6em;}

The Joys of Art

Tuesday, March 21, 2006

Coastal Recovery


Coastal Recovery---Senator Mary Landrieu



This is for all my peoples who are still hurting and crying and this is also for the people are talking much shidt about Louisiana and New Orleans....Yeah I know who you are.....Ooooooohhhhhh.... A play on words....See news article below....

Levees not built to dam standards

By Bob Marshall
Staff writer

As they near the end of their investigations into the deadly failures of New Orleans' hurricane protection system during Katrina, some of the nation's top engineering minds have come to one unshakable conclusion: If the Army Corps Engineers had built the region's levees to same standards it uses for dams, the city may well have survived Katrina without catastrophic flooding.

Representatives of the American Society of Civil Engineers and the National Science Foundation said Monday that some of the problems they believe played key roles in the disaster - low engineering safety standards, lack of rigorous peer review and shoddy maintenance - are simply not tolerated by the corps when building dams, but are common place in levee projects.

"If you looked at a major earthen dam being designed during the same time frame as the 17th Street canal (floodwall) was being designed, there would have been boards of consultants and rigorous outside peer review that probably would have detected and caught many problems that are coming to light with the 17th Street project," said Larry Roth, deputy executive director of the society.

"There is a National Dam Safety Act that sets out specific requirements to make sure dams won't have these problems, that they are safe for the people who live around them. There is no similar legislation for levees.

"We're hoping one of the good things that comes out of Katrina is that the country finally recognizes the fact that levees protect as much human life and property as dams."

Roth made his comments during a meeting of the National Research Council, an arm of the National Academy of Sciences, which is providing scientific peer review of work being done by the Interagency Performance Evaluation Task Force, the corps-sponsored panel investigating the failures. The council was meeting in New Orleans to hear task force team leaders provoked an update of its work to date, which will be part of a comprehensive report scheduled to be completed June 1.

But the council also asked for updates from the society of engineers, which was designated to provide ongoing review of the task force, and the National Science Foundation, which is conducting an independent investigation of the failures. While spokesmen for both organizations had high praise for the task force effort overall, they urged the council and the corps to address what they considered an major underlying cause for the disaster - the nation's low priority for levee safety.

Ray Seed, a University California-Berkeley professor who is a leader of the science foundation investigation, said this was "a very huge issue."

"The corps actually has a very elegant set of policies set up for dam review and they do a very good job of it," Seed said. "They bring in an outside panel of experts with great knowledge and experience in specific areas of science and engineering critical to building dams.

"They are independent of the corps and they do rigorous review of everything. Dams also have outside review panels meet every few years to review the safety of the dam and the maintenance efforts.

"We would like to see the same thing in place for levees, because they protect just as many - maybe more - human life and property as dams."

National Science Foundation and American Society of Civil Engineers team members, as well as the state's Team Louisiana investigators, have pointed to information uncovered by investigators which they said is evidence of sloppy engineering and weak peer review. Seed and Roth said those have included floodwall sheet piling supports that were not driven below the bottom of the 17th Street canal; soil investigations that were not thorough enough for the complicated soils resulting in overly optimistic estimates of soil strengths; lack of soil borings at the levee toes that caused the design teams to miss a weak layer of soils that contributed to the breach on the 17th Street canal; poor communications between outside engineering firms and the corps; poor levee maintenance that allowed encroachment by trees and swimming pools onto the rights of way.

Even the basic engineering safety standards applied to levees is less than that allowed for dams, they said.

"Why have a factor of safety less rigorous for levees?" Roth asked.

The "factor of safety" is the standard technique engineers must use to account for unforeseen variables that might impact their designs, such as defects in materials or uncertain soil conditions. That results in "over-engineering" or overbuilding - using components stronger than the physics of the project call for, or including redundant systems, just to be safe. The higher the factor of safety, the less likely a design is to fail. For example, a levee that uses a T-wall normally has a higher factor of safety than an I-wall, which was the design used in many of the areas that were breached.

But because costs increase as the factor of safety rises, the profession has established a scale of appropriate factors of safety for different types of structures, with the prime consideration being the cost of failure - in terms of dollars, and lives. But while dams have a stringent factor of safety, levees have had lower demands. Traditionally, the factor of safety is 1.3 - whether the levee is protecting a dairy farm or a major city, such as New Orleans.

That difference, Seed and Roth agreed, points to a systemic problem in the way the levees have been built and maintained.

"It's very much like what was discovered in the investigation of the space shuttle disasters," Seed said. "The system has to be changed to prevent this from happening again.

"The problems the system created for New Orleans can probably be found in every levee system in the country," he said.

Bob Marshall can be reached at rmarshall@timespicayune.com or (504) 826-3539.


Print | Send To A Friend | Permalink (Learn More)

0 Comments:

Post a Comment

<< Home