By Laila Kearney
SAN FRANCISCO, June 21 (Reuters) - Demolition crews on Friday began work on the biggest dam removal in California, a project aimed at protecting homes threatened by the aging, obsolete structure and restoring spawning grounds for native trout.
Plans call for the 94-year-old San Clemente Dam, built on the Carmel River about 120 miles (190 km) south of San Francisco, to be torn down in stages over three years, followed by rerouting of the river around the dam site and wildlife restoration.
"In 10 years, when you come to the site, you won't be able to tell there was a dam there," said Jeff Szytel, founder of contractor Water Systems Consulting, who is overseeing the project.
The demolition is part of a larger safety and restoration effort that will include removal of a smaller dam downstream from San Clemente and recycling of sediment that has built up in the reservoir behind the dam.
The dam was designed to divert Carmel River water to the Monterey Peninsula, but with the reservoir nearly filled with silt that purpose is now carried out through groundwater pumping.
The 106-foot-tall (32-metre-tall) concrete arch dam was deemed seismically unsafe in the early 1990s by the California Department of Water Resources, which concluded that roughly 1,500 homes and public buildings downstream were vulnerable in the event of a major flood or earthquake.
The San Clemente is roughly twice as high as the 55-foot-tall (17-metre-tall) dam dismantled in the early 1970s near the northern California coastal town of Eureka, the largest previously removed in the state, Szytel said.
Tearing down the San Clemente Dam will enable the reopening of 25 miles (40 km) of creeks and tributaries in the Carmel River watershed, allowing Central California Coast steelhead trout, listed as a threatened species, to return to native spawning areas.
The project's cost, estimated at $84 million including wildlife restoration, will be shared between the dam's current owners, the state and federal government.
Groundbreaking on the San Clemente removal follows federal recommendations to remove four hydroelectric dams on the Klamath River in Oregon and California to resolve water allocation disputes and restore habitats for Coho salmon and other fish. (Editing by Steve Gorman and Mohammad Zargham)