Moccasin Reservoir Stabilized Following Threat of Dam Failure
San Francisco, CA—A small dam and reservoir in Tuolumne County is stable tonight after heavy rainfall earlier today sent a major surge of water and debris into the system, threatening the failure of the dam. The Moccasin dam functioned properly under this natural stress and at no time was there any threat to the Bay Area’s water supply.
Early Thursday (March 22) afternoon, the San Francisco Public Utilities Commission (SFPUC) activated its emergency action plan at SFPUC-owned facilities after crews observed water leaking 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.
The water level in the Moccasin reservoir has significantly decreased since the initial incident and the SFPUC has started draining the Moccasin reservoir into the much larger Don Pedro Reservoir. At the same time, crews are actively inspecting the current state of the dam and the extent of any damage to it and its spillways.
Moccasin Reservoir is one of the SFPUC’s smallest reservoirs and is used for regulating the Hetch Hetchy water system.
Media availability Thursday night
Tonight at 8 p.m., SFPUC Assistant General Manager for Water Steve Ritchie will be available for on-camera media interviews at SFPUC Headquarters located at 525 Golden Gate Avenue.