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Facing flood threats from Isabella Dam
Downtown could be submerged by 10 to 20 feet, engineers say
| Tuesday, Oct 30 2007 10:55 PM
Last Updated: Tuesday, Oct 30 2007 10:59 PM
If the auxiliary dam at Isabella Lake collapsed when it's filled to its allowed limit, downtown Bakersfield would face floodwaters 10 to 20 feet deep.
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Those are the findings in a preliminary inundation report delivered to county supervisors Tuesday by officials with the U.S. Army Corps of Engineers.
The rest of Bakersfield, and most of the San Joaquin Valley floor out to west of Interstate 5 would be five to six feet deep, corps officials said.
It would take six to 12 hours for water in Bakersfield to rise to one foot deep, the depth at which escaping by car would become problematic.
After that the water would continue to rise.
It isn't certain how long it would take for the water to dissipate if the lake were filled to the maximum 360,000 acre feet allowed by the corps.
A final copy of the report released Tuesday, with other scenarios, is due in January said corps geologist Ronn Rose.
"This information is preliminary and it is draft. This is one scenario we have for you today," Rose said.
He said the scenario shown Tuesday is the "most likely" of the extremely unlikely scenarios that lead to a dam failure and massive flooding of communities in the Kern River Valley and Bakersfield metropolitan area.
Isabella Lake dam sits on an active earthquake fault and seepage at the dam has been discovered.
Rose said the dam is one of the top six at-risk dams in the nation.
In addition to the inundation study, the corps is doing detailed seismic and seepage studies of the dam and looking to determine if the structure needs to be repaired or replaced to be made safe.
Supervisors said they want the public informed about what could happen as soon as possible.
Supervisor Jon McQuiston wanted to know why, even though the data isn't finalized yet, the county can't begin pulling together a plan to evacuate residents ahead of the floodwaters.
Fire Chief Dennis Thompson said there are already evacuation plans and work has begun to "tweak" those plans with the new flood data developed by the corps.
Then public meetings will be held and the plan publicized so people understand how to get to safety.
Supervisor Ray Watson said it is time to develop best-guess evacuation plans and get flooding information to the pubic while the corps works to refine its numbers.
Plans can be updated, he said, as new information comes in.
Other supervisors called for the public release of the preliminary draft of the flood study to the public.
Officials with the corps refused to release the information, but county officials did later in the day.
"Once it goes to the county I can't say what the (release) procedures are," Rose said.
"The corps will not release directly to the public. We don't want terrorists to know the best places to blow up."
But Kern County Counsel Bernard Barmann said the information is now public since it was publicized at a public meeting of a government body.