The potential for gate failures at two aging dams has led El Dorado Irrigation District officials to declare emergencies at Caples and Silver lakes.
If the gates fail, people on the waterways below the dam could be endangered. Loss of the water – more than a third of the water agency's storage – could affect power-generating capability and recreation on the lakes.
The water agency serves about 100,000 customers in El Dorado County.
The move, approved at a special meeting last week, is intended to hasten repairs to gates that control water releases from the two dams, built in the 1920s. Uncontrolled releases could cause unseasonably high flows into Caples Creek and the Silver Fork of the American River.
"We do not have(the threat of) dam failure," said Jake Eymann, an engineer and acting co-manager of the district's hydroelectric division. But he said underwater inspections June 10 and 11 disclosed serious deterioration of gates and other devices that control water storage and releases.
Caples Lake in Alpine County and Silver Lake in Amador County are a few miles from each other, off Highway 88. They are part of a system of lakes, canals and a powerhouse the district purchased from Pacific Gas and Electric Co. in 1999.
Although the approximately 22,300-acre-foot Caples Lake and 8,700-acre-foot Silver Lake represent about 38 percent of the district's water storage capacity, the supplies are used primarily for power generation rather than drinking water, said district spokeswoman Deanne Kloepfer. An acre-foot is the amount of water needed to cover an acre to the depth of 1 foot.
At Caples Lake, last month's inspections by camera-equipped divers revealed that brass seats for a lower slide gate were missing, causing excessive leakage and vibration, a staff report said.
A video of the inspections presented during the board meeting showed corroded metal and a dislodged and bent trash rack, designed to catch debris.
At Silver Lake, an inspection found that steel bracing for the outlet tower had failed due to corrosion and gate stems were severely corroded, Eymann said.
At Caples Lake, he said, staff members will avoid operating the lower of two gates because they are on the verge of failure.
The emergency declaration, under state law, allows the district to contract for services and equipment without competitive bids. It also exempts the project from California Environmental Quality Act review.
Staff members said they will have to obtain approvals for the work from the Federal Energy Regulatory Commission and the state Division of Safety of Dams.
Because many of the replacement parts may have to be custom-made, Eymann said, the repairs likely won't happen for at least a year.
"Even expedited," he said, "this will not meet normal expectations for a quick project."
Call The Bee's Cathy Locke, (916) 608-7451.
