U.S. Issues Warning About Flood Threat From Casitas Dam

Federal officials are pressing ahead to shore up the dam that holds back Lake Casitas before a strong earthquake strikes, a threat that could lead to a flood disaster for people living along the lower Ventura River.

The final environmental report released Monday by the U. S. Bureau of Reclamation describes the hazard posed by the quake-prone dam seven miles north of Ventura.

Under a worst-case scenario--a magnitude-7 quake on the nearby Red Mountain fault--a dam rupture would release a 300-foot wall of water into Coyote Creek, killing about 400 people and causing $430 million in property damage by the time the torrent reached the ocean.

The base of the dam consists of wet, sandy soils that would probably turn Jell-O-like if jiggled violently in a temblor. The dam is one of 40 that the bureau has identified as quake-prone in California, Oregon and Nevada.

“If something did happen, there is a large potential for loss of life,” said William Pennington, Casitas Dam project manager for the bureau. “It would be an ugly situation.”

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Beginning May 14, the agency plans to begin work to strengthen the 334-foot-tall dam, removing spongy soil and replacing it with firm earth. The job will cost $42 million and be completed by December 2000, Pennington said.

Pat Baggerly of the Environmental Coalition of Ventura County said her organization is concerned about dust from the project and where soil will come from to buttress the dam. Further, she said a permanent flood-warning system should be installed, instead of the temporary network of sirens and alarms that the bureau is considering for the Ventura River.

The group has not decided whether to challenge the environmental study, but such a move probably would delay the dam repairs.

Casitas Dam, built between 1956 and 1959, provides water to 40,000 users in Ventura County. The water it stores provides $30.6 million in annual benefits, one-third from recreational boaters and fishermen, and the rest from municipal, industrial and agricultural users.

Short-term remedies in place to reduce the quake risk include dewatering wells to help dry out soils and a reduction in the volume of water kept in a spillway catch basin.

For a copy of the Casitas Dam report, contact the bureau at (209) 487-5133.