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SFPUC Monitoring Potential Moccasin Dam Failure
Posted Date: 3/22/2018 4:30 PM


satellite image of area surrounding Moccasin
San Francisco, CA—The San Francisco Public Utilities Commission (SFPUC) is monitoring an active situation this afternoon at the Moccasin Reservoir, which is a small reservoir for regulating water system flow in Tuolumne County.

There is no threat to the Bay Area’s water supply at this time, and all people potentially in harm's way have been evacuated out of an abundance of caution. The dam has not overtopped and is still intact.

Here is the latest information available right now:

Just before 1 p.m., heavy rainfall caused a major surge of water to flow into Moccasin Reservoir causing the reservoir elevation to rise and a large amount of debris entered the reservoir. The excess water was spilling over both the primary and emergency spillways as designed.

SFPUC immediately dispatched a team to monitor how the Moccasin dam was performing and observed leaking on the downstream face of the dam.

At 1:15 p.m., the SFPUC activated its prepared emergency action plan and is following those procedures.

At 1:30 p.m., evacuation ordered for all people in potentially in harm’s way, including at the Moccasin Fish Hatchery and Moccasin Marina.

The SFPUC is closely monitoring the water level and the reservoir is currently receding as of 4:05 p.m.

If there is an actual dam failure, which is considered unlikely as of 4:05 p.m., all of the water would be safely captured by the Don Pedro Reservoir and would not affect any additional people.

SFPUC is actively coordinating with Turlock Irrigation District, Tuolumne County Sheriff’s Office and other authorities in the area.

SFPUC to provide update at 5:45 p.m. today

The SFPUC will provide an update to media via a conference call at 5:45 p.m. today.