Useless Dam Presents Dilemma for California

A pile of sediment has built up so high behind The Matilija Dam that even if an inch of rain falls, water spills over in glistening cascades, according to a report in the Associated Press.
Moreover, the dam's aging concrete also chokes off sediment and nutrients that could nurture the riverbanks and restore Ventura County beaches downstream.
However, tearing down the Southern California structure presents a costly challenge. The removal, according to the report, is one of the most complicated in the country, and the project will carry an expected price tag of $130 million.
Steve Evans, conservation director of the Friends of the River, which monitors dam removals across California said, "It's not just something that you can go in there and remove in a day."
Environmentalists and engineers agree the Matilija Dam has outlived its intended purpose, according to the Associated Press. Officials said that demolishing the 198-foot-high dam would ultimately improve the area's ecosystem–helping restore endangered steelhead trout by allowing them to swim upstream and spawn, and allowing sand to flow downstream and restore eroded beaches.
Jeff Pratt, director of the Ventura County Watershed Protection District, said the sediment makes the reservoir all but useless. The protection district is leading the removal effort. Plans to remove the Matilija meet state coastal protection requirements.
The dam was built in 1947 as a means of providing flood control to a handful of small downstream communities and recharging groundwater supplies used by farmers in the sparsely populated Ojai Valley. Today, the dam cradles mostly rocks and pebbles, and is clogged with 6 million cubic yards of sediment.
Part of the Matilija is already gone. Workers took out slabs built with substandard materials, reducing the dam's height to 165 feet in the middle. As the rest is removed, the watershed district will take steps to avoid flooding along the 16 miles of the Ventura River that leads to the Pacific Ocean, according to the report.
Nationally, at least 145 aging dams have been torn down in the last five years for a host of reasons, including safety.
The Matilija's removal won't begin until at least 2007. A proposed plan has been presented for public comment, and funding will need to come mostly from Congress. To help what fish remain, engineers designed a series of small pools leading to a holding pond where the trout would be picked up and driven upstream by truck. But rocks carried over the dam by water broke the fish ladder, said the report.
According to Pam Lindsey, a watershed district ecologist, the leading proposal for removing the dam calls for gradually pumping 2 million cubic yards of mud to the flood plain downstream. After temporarily stabilizing the rest of the sediment, crews would break the dam down a section at a time.

Associated Press

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