San Francisco, CA—The situation affecting the Moccasin Dam and Reservoir in Tuolumne County over the past 24 hours is stable today as crews continue to monitor the condition of the dam and water levels in the Moccasin Reservoir. There continues to be no impacts to the Bay Area’s water supply.
“I was closely monitoring the developments at the Moccasin Reservoir on Thursday,” said Mayor Mark Farrell. “The SFPUC responded in a swift and effective manner. I commend all our employees for their work to control this potentially dangerous situation.”
Early yesterday afternoon, the San Francisco Public Utilities Commission (SFPUC) activated its Emergency Action Plan at the SFPUC-owned facilities after crews observed water seepage on the downstream face of the Moccasin Dam. In coordination with local officials, the SFPUC ordered an evacuation for all people who were potentially in harm’s way, including at the Moccasin Fish Hatchery and Moccasin Marina. The dam itself never overtopped and remains intact.
Last night, representatives from the California Department of Water Resources (DWR) Division of Safety of Dams (DSOD) arrived on site for dam evaluation and inspection of potential damage. Those inspections are continuing throughout the day.
The evacuation notice for Moccasin staff was lifted as of 7 a.m. today and SFPUC staff is working at Moccasin today. The evacuation order for Moccasin Marina and the residences associated with the Fish Hatchery, downstream of the dam, are still in effect until further notice.
The National Weather Service is calling for possible rainfall this evening and SFPUC staff is preparing for any additional rain-related stress on the Moccasin Dam or Reservoir. Should that occur, any excess water that could not be handled by the dam or its spillways, would be safely captured by the Don Pedro Reservoir.
SFPUC’s immediate priorities are to continue to reduce the water level in Moccasin Reservoir, closely monitor and inspect the dam’s condition, the Moccasin Reservoir and its spillways, and the dispatching of teams of repair crews to remove debris and perform temporary repairs.
Moccasin Reservoir is one of the SFPUC’s smallest reservoirs and is used for regulating the Hetch Hetchy water system.
SFPUC staff continues to actively coordinate with local authorities, including Turlock Irrigation District, and the Tuolumne County Sheriff’s Office.