At 10:45 on Aug 3, 2014 the Twain Harte Dam operator notified Tuolumne County Emergency Services officials regarding a crack reported on one side of the dam. Tuolumne County then issued an emergency alert.
At this time there is no threat which is reported regarding a catastrophic dam failure, however, the onsite water officials have decided to reduce the level of the lake behind the dam by at least ten feet. Ten feet would be equal to roughly half of the deepest section of the lake which is between twenty and twenty-five feet at its deepest point. Twain Harte Lake holds approximately 142 acre feet of water when it's full. The release of an additional 2,000 gallons per minute should attain the ten foot drop in two days time.
Emergency officials were reported on local radio to have stated there is a crack which appeared in the dam, near the top, along with a crack in a granite rock which the dam abuts on the southern portion of the dam.
Flood warnings were initially issued this morning for the areas below Twain Harte Dam, which included the Belleview Creek and Sullivan Creek drainage's. There are multiple subdivisions in both areas and a large number of homes which would have been affected. The Tuolumne County Sheriff's Office has not ordered any evacuations at this time.
“As the water goes down, we’ll get to a point where state inspectors will be able to inspect the complete structure of the dam,” says Tuolumne County Sheriff Jim Mele. “At this point, we don’t see any imminent structure failure, or dam breakage.”
Because the water in the lake is not used as potable water, part of the water being drained will run directly to two area creeks. Both Twain Harte Creek and Sullivan Creek will be able to accept the increased flow without danger of flooding, and the ater from both will wind up in Phoenix Lake Reservoir, which is a potable water storage site. The bulk of the water however, will eventually wind up in Don Pedro Reservoir which is a recreational reservoir site.
All residents in the county are being urged to not visit the site since the lake is closed until further notice.