A daily compilation of significant news articles and comment
March 27, 2008
3. Watersheds
Panel urges river reroute; San Clemente Dam: Multiphase removal estimated at $83 million -
QUAGGA MUSSELS:
Outdoors Column: Cachuma Lake remains open to boaters; The Santa Barbara Board of Supervisors votes to allow trailered boats at the lake, once they've passed inspection for the invasive quagga mussels - Los Angeles Times
Panel urges river reroute; San Clemente Dam: Multiphase removal estimated at $83 million
By Kevin Howe, staff writer
Complete removal of the San Clemente Dam and rerouting of the
Trish Chapman of the state Coastal Conservancy, Monica Hunter of the Planning and Conservation League Foundation, and Joyce Ambrosius of the National Marine Fisheries Service, presented what they believe is the final version of a project to solve the problem of the silted-up dam.
Conservationists say the dam blocks the upriver spawning migrations of steelhead trout and the downward flow of sediment to replenish the river bottom.
The panel presented its proposed solution to a group of
The removal and rerouting project will cost an estimated $83 million, Chapman said, $49 million to be paid by California American Water, owner of the dam, and the rest by state, private and possibly federal funds.
The dam was declared unsafe in 1992 by the state Department of Water Resources' Division of Safety of Dams, which reported that the dam could give way in an earthquake of magnitude 5.5 on the Tularcitos Fault, which it straddles, or from a magnitude 7 quake on the
Alternatives to stabilizing the dam had included doing nothing; shoring up the dam to strengthen it against a future earthquake; "notching," or cutting down the dam partway to relieve the pressure of accumulated water and silt behind it; tearing the dam down entirely and hauling off the sediment; and rerouting the
Chapman said combining dam removal and river rerouting would solve several environmental problems.
Currently, migrating salmon must negotiate a long, high fish ladder to get over the dam to the upper river.
Taking the dam out would open up an easier path for the fish.
But demolishing the dam without rerouting the river poses the prospect of letting 87 years worth of accumulated silt suddenly wash down the river, which would likely cause flooding and raise the riverbed downstream, she said.
San Clemente Creek runs parallel to the Carmel River, separated from it by a ridge of land, and Chapman said the plan is to cut through the ridge upstream to let the river flow into the creek, use the tailings from the channel cut as material to build a diversion berm to force the river water into the creek and, once that's accomplished, begin taking the dam down.
In addition, an 1880s-era smaller dam downstream would also be removed, she said.
The accumulated sediment behind the San Clemente Dam would remain in place, stabilized by piling the broken concrete from the dismantled dam against it.
Once the river is opened, the fist-sized stones — "cobbles" — that form the necessary spawning grounds for steelhead in the riverbed downstream will again be freed to move into the lower river by the water flow, Chapman said.
Dealing with the accumulated sediment behind dams that have outlived their usefulness, she said, is "an issue throughout the West."
San Clemente Dam was built in 1921 to hold back 2,000 acre-feet of water. Now its sediment-filled reservoir holds about 125 acre-feet of water. The rest is rock and mud.
The dam has been subject to overspilling during high flood seasons, according to state engineers, and water running over the top could erode rock on either side, causing the dam to break.
A 1997 analysis by state safety experts indicated a dam failure would send 100 to 150 acre-feet of water and a flood of mud downstream as far as
In 2004, the dam was pierced with pipes to drain off water behind it, but they didn't provide enough of an opening to prevent water from washing over it during floods.
The dam has been fitted with instruments to detect earthquakes that will issue an automatic warning to fire stations downstream so that residents along the river can be notified of flood danger.
The cheapest alternative is to pile earth against the existing dam, buttressing it against failure. That alternative would cost an estimated $49 million, which is how Cal Am's share of the removal project was determined.
Buttressing, Chapman said, would not eliminate the steelhead migration or sediment flow problems caused by the dam.
Cal Am also will deed 5,400 acres behind the dam between
The dam removal project would be done in phases, Hunter said. It would include improvements to access roads and site preparation the first year, cutting the diversion channel with excavation of sediment from San Clemente Creek the second year, and reconstruction of the creek with "step pools" for the fish migration, habitat restoration and removal of the dam during the third year.
There would be no need to truck out sediment, and the sediment left in place would be stabilized by the dam rubble and by tree planting, she said.
The Coastal Conservancy's role in the project would be providing design and engineering services, the National Marine Fisheries Service would assist with permits, and Cal Am would undertake the construction and demolition work.
At the end of the project, "the dam will be gone and it will look like the river canyon before it was built," Ambrosius said. #
QUAGGA MUSSELS:
Outdoors Column: Cachuma Lake remains open to boaters; The Santa Barbara Board of Supervisors votes to allow trailered boats at the lake, once they've passed inspection for the invasive quagga mussels
By Pete Thomas, outdoors columnist
The Santa Barbara County Board of Supervisors today voted to allow trailered boats at
As was the case at Casitas before the Casitas Municipal Water District voted three weeks ago to impose a controversial one-year ban, vessels arriving at Cachuma must be clean and dry upon arrival or face quarantine.
Boats longer than 24 feet, those with out-of-state stickers or registered in close proximity to quagga-infested lakes will be quarantined on site for 14 days before being allowed onto the reservoir.
"Before anybody complains about these new procedures and rules, I caution them to stop and consider the alternative," said Tom Raftican, president of the United Anglers of Southern California, which argued against a ban at both reservoirs. "I bet the folks around
Quagga mussels, which multiply rapidly, clog pipes and alter ecosystems, have infested reservoirs along the Colorado River and appeared in Southland reservoirs fed by the
Casitas became the first to ban launching of private boats as a safeguard against accidental introduction, despite objections from the Department of Fish and Game and pleas from anglers and business owners in Ojai and Oak View.
Some on the Casitas board expected its decision to create a domino effect and force the financially strapped DFG to take a more active role in combating the spread of invasive mussels. #
http://www.latimes.com/sports/la-spw-outshort27mar27,1,2941167.column
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