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Study backs Corps' review of failure risk

BY JAMES BURGER, Californian staff writer
e-mail: jburger@bakersfield.com | Friday, Nov 9 2007 9:15 PM

Last Updated: Friday, Nov 9 2007 9:17 PM

Isabella Dam deserves its place on the list of the country's six most at-risk dams, according to an independent review of conditions at the dam at Isabella Lake released Friday.

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Photo by Casey Christie

Seepage and leaks have been detected around Isabella Lake's auxiliary dam, officials say.

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• Read the external review panel report on the stability of Isabella Dam

The review supports the U.S. Army Corps of Engineers' decision to put the Isabella Dam on a short list of dams with the highest risk of failure in the nation.

The panel, made up of six dam experts, has been reviewing the work of the Corps on high-risk dams across the United States -- and visited the Isabella Dam in April and May.

Their report supports the Corps' decision to reduce the amount of water stored at the dam on the Kern River above Bakersfield and the community of Lake Isabella. It also encourages the Corps to continue its detailed investigation into the possibility of dam failure and the damage a collapse could cause.

John Vrymoed, chief of the design branch of the California Division of Safety of Dams, was one of the panel members.

"I think that the Corps is to be complimented on their pro-active handling of this problem," Vrymoed said.

The biggest problem at Isabella Dam, according to the independent report, is the auxiliary dam -- one of the two compacted earthen structures that make up the Isabella Dam.

Studies being conducted, and readings from monitoring equipment, seem to show seepage and leaking along the conduit that carries water through the auxiliary dam, the report states.

Those leaks could lead to "piping" -- a condition where water eats a channel through a dam, leading to a collapse.

In addition, the auxiliary dam has "poor foundation conditions, which exist over the entire foot print of the dam."

The upper 20 feet of the auxiliary dam's foundation is loose and could be weakened in an earthquake, the report states.

The auxiliary dam sits only a few thousand feet above homes in the community of Lake Isabella.