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[whitespace] Dam Problems

Los Gatos--The dam at Lexington Reservoir isn't failing. That was the first thing Santa Clara Valley Water District engineers determined about the most recent problems inside the dam. But the rest remains a mystery.

After checking out a 1,500 foot long pipe that runs through the middle of Lenihan Dam at Lexington Reservoir, inspectors found that sections of the pipe were starting to buckle under outside pressure. A team of divers has been crawling up inside the 52-inch wide pipe this week to conduct a series of hourly pressure tests around the clock and to install pressure gauges.

"This isn't something we expected to find," says Mike DiMarco of the water district. He says the investigation should be wrapped up in a month or two.

Engineers aren't sure what caused the problem, which is the third instance of buckling in the pipe since the 1989 Loma Prieta earthquake. Ron Delparte, chief of field engineering for the state Division of Safety of Dams, says what's happening is "kind of unexplained."

The situation is further complicated, he says, by the complex alignment and grade of the pipe, which is encased in a foot-thick concrete sleeve that follows the contours of rock formations through horizontal and vertical bends.

The water district has theories about the cause, but hasn't found anything conclusive yet. One theory is that the steel used to build the pipe in 1952 may have been of inferior quality because the Korean War was on at the time. Engineers are investigating another theory--that an air vent connected to the main pipe may not be big enough; and also looking into the possibility that the problem may linked to recent seismic activity or changes in the soil in the earthen dam.

For the sake of the fish in Los Gatos Creek--especially the salmon that are starting to spawn in Guadalupe River, which collects water from Los Gatos Creek--about 26,000 gallons of reservoir water per minute is being pumped over the spillway to keep the creek flowing while the outlet pipe is closed.

DiMarco says the reservoir will not be drained, however, so that the engineers and divers can keep testing the pipe. "There's no chance of draining it at this point, but we may in the future to get the fix done," he says.

Once the water district figures out what the problem is, the next step will be to figure out how to operate the dam if the pipe is still closed when the winter rains begin. "If we get so much rain that we can't release it, the reservoir will spill sooner than anticipated," DiMarco said.

Local police, fire and other emergency agencies were alerted to the troubles at the dam, and the water district has partially activated its Emergency Operations Center, DiMarco said. Officials are holding conference calls each morning and afternoon to keep other agencies and cities informed.

DiMarco said he put out the alert so that government and law enforcement officials would know that there was no threat to public safety after he heard a conversation on his police scanner between a park ranger and a sheriff's deputy who thought that the increased activity at the dam might mean it was getting ready to fail.
Jeff Kearns

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