Dam Demolition Is Put at $130 Million

The 190-foot-high Matilija Dam in Ventura County can be removed over three years at an estimated cost of $130 million, according to a new study that examines the environmental benefits and challenges involved in demolishing the aging structure.

To minimize the possibility of downstream flooding, levees would have to be built or made taller in Meiners Oaks, Live Oak Acres and Casitas Springs; bridges would have to be altered; and in a few areas, structures and land purchased, according to the environmental report.

To maintain water quality at nearby Lake Casitas, a complex silt diversion and filtering system would have to be constructed.

Fish and animals along the 17-mile-long Ventura River watershed would be temporarily stressed by the demolition, the report found. But the dam’s removal would improve the Ventura River’s ecosystem in the long run, said the study, prepared by the U.S. Army Corps of Engineers and the Ventura County Watershed Protection District.

The Matilija project is the largest and most ambitious of a fledgling movement by environmentalists to remove federal dams that are no longer needed for power, water storage or flood control.

“On a national level, no past or planned dam removal project matches the Matilija project,” said Steve Rothert, associate director of the environmental group American Rivers.

Chief among the benefits from the dam’s removal would be restoration of endangered steelhead trout runs and replenishment of Ventura’s sand-starved beaches, the study says. Federal, state and local officials have been working on the plan for three years, with support from several environmental groups that have long advocated removal of the structure, which is clogged with 6 million cubic yards of sediment.

“This is the next big step and it’s an important one,” said David Pritchett, spokesman for the Southern California Steelhead Coalition. “We especially like that the dam removal will only take two years so that we can get fish passage reestablished promptly.”

The entire process -- demolishing the dam and restoring Matilija Creek and the Ventura River to their original course -- would take about three years, the report’s engineers estimated.

Heavy rains could cause delays, they said.

The report’s release kicks off a 45-day public review period that includes a hearing July 28. Proponents are eager to wrap up the review process by year’s end to qualify for $79 million in federal funds that would cover much of the demolition cost.

The remainder would be picked up by state and local sources, officials said.

Federal funding has been approved by the House and by the Senate’s Environment and Public Works Committee, but must still be approved by the full Senate and signed by the president. Project advocates say the earliest that work could begin would be 2007.

Built in 1948, the dam has trapped so much sediment that its capacity to hold water is diminished.

Getting rid of the millions of cubic yards of fine silt, sand and rock behind its concrete wall is a technical challenge that will have to be carried out carefully, the report says.

After considering several alternatives, officials settled on a two-pronged plan that would drain about one-third of the silt through a slurry pipe.

Sludge would be deposited along the banks of the river downstream, while precautions would be taken to filter murky water before it enters Lake Casitas, which provides water to 75,000 residents in Ventura and Ojai.

A 100-foot-wide channel would be carved into the reservoir’s remaining sediment and rock to form the new creek bed. Engineers say excess sediment would gradually be washed away during rainstorms and swept out to the ocean, restoring beaches that have eroded.

Though downstream flooding is not likely during normal winter rains, the reconfigured channel could pose a risk during a rare heavy storm, the report found.

To protect downstream communities, a new levee would be constructed in Meiners Oaks and existing floodwalls at Live Oak Acres and Casitas Springs would be raised.

Matilija Hot Springs, a former county park, and six residential tracts in the Camino Cielo neighborhood just below the dam would have to be purchased and razed because of the high risk of flooding during a heavy storm, the report’s authors recommend.

Supervisor Steve Bennett, whose district includes the project area, said the reconfigured levees would provide a higher level of protection than now exists.

“The county is simply not going to move forward with projects that increase the county’s liability with flooding,” he said. “From a public safety standing, people will benefit from this.”