Work Behind Schedule to Strengthen Casitas Dam

Work to strengthen the dam holding Lake Casitas has slipped behind schedule, and a federal official Thursday said construction must commence soon if crews hope to complete critical tasks before winter storms arrive.

Reinforcement work on the dam, which is vulnerable to a moderate earthquake, was set to begin in June.

However, environmental concerns and delays in gaining approval for a flood early warning system, in the event the dam collapses, mean that work will not start until late this month, said Bill Pennington, project manager for the U. S. Bureau of Reclamation.

The dam was built near Oak View in 1959, but recent seismic tests show that soil beneath it is unstable. The bureau ranks it as one of the most quake-prone dams in the western United States.

If it topples, the dam would send a wall of water up to 85 feet high down the Ventura River to the Pacific Ocean, threatening 14,000 residents in downtown and west Ventura, according to government estimates.

“The ground under the dam is too soft. It’s like quicksand, and you put that dam on top of quicksand and it’s going to fail,” Pennington said.

Residents and local officials have asked that a network of eight sirens be installed to warn them in case of a flood.

Part of the dam will be removed during construction, making the structure temporarily weaker than it now is, officials say.

Ventura officials gave final approval for the sirens Wednesday. They will be installed along the river in the next three weeks at a cost of $300,000 and should be ready for testing by the end of the month, Pennington said.

In June, the Environmental Defense Center in Ventura threatened to sue the bureau for allegedly failing to conduct an adequate environmental review of the project. The group contended that dirt removed from a 130-acre portion on the west side of Lake Casitas to be used as fill material for the dam would have resulted in destruction of oak trees and native animal species.

Negotiations between the bureau and group led to a compromise in which the Interior Department agreed to minimize impacts to wildlife and plants and to restore the area once the project is finished, said John Buse of the Environmental Defense Center.

Now that those obstacles have been resolved, Pennington said, critical parts of the work can begin by the end of this month.

Work crews already at the dam have begun preliminary earth moving, clearing away rock and debris from the base of the dam, grading pads for equipment storage and installing wells to suck out water that had seeped beneath the dam, Pennington said.

Montana-based Barnard Construction Co. was awarded a $21-million contract in June to strengthen the dam. Adding design, engineering and other costs, the entire Casitas Dam improvement project will cost $42 million, according to the Interior Department.

By the end of the month, crews expect to begin excavating soggy soil from beneath the dam. It must be removed, compacted and put back in place to reduce the risk of collapse, Pennington said. The work will slightly weaken the dam and it must be completed before rains come, he added.

“We want to make sure that dam is at least as safe or safer than it is now by mid-December,” Pennington said.

Next year, crews plan to use the dirt removed from the lakeside to bulk up Casitas Dam, making it more quake-resistant. A giant berm will also be installed at the base of the dam like a big doorstop to keep it in place, Pennington said.

Meanwhile, at nearby Matilija Dam, progress continues on exploring ways to remove the structure, located in a canyon above Ojai. Ventura County lawmakers met Wednesday with the Interior Department to discuss how to proceed with a multi-agency study.

Matilija Dam was built in the 1940s to control floods and store water in the Ventura River watershed. It has come under increasing scrutiny because it is full of mud, cracking and of little use any more.

The dam does not pose a flood risk, but does block access to spawning grounds for migratory steelhead trout, an endangered species, and prevents sand from reaching beaches. Consequently, environmentalists, surfers, fishermen, politicians and some business leaders want it removed.

Local, state and federal officials met last week in Ventura to launch a study on whether it is cost-effective and environmentally beneficial to remove the dam.

This week, Rep. Elton Gallegly (R-Simi Valley), Supervisor Kathy Long and county Public Works Director Art Goulet met with Patricia Beneke, assistant Interior secretary, to discuss how to coordinate the various agencies interested in the project.