The Briones Reservoir inlet/outlet tower is located in Briones Reservoir, an approximately 60,000 acre-foot raw water storage facility operated by the East Bay Municipal Utility District (EBMUD) in unincorporated Contra Costa County to the north and east of the City of Orinda. The tower is located about two hundred and fifty yards upstream of the dam crest. This tower conveys raw water from Lafayette Aqueduct No. 2 to Briones Reservoir, and from Briones Reservoir to Orinda Water Treatment Plant for treatment and distribution to EBMUD customers. Constructed in 1964, the tower is a concrete structure that is about 230 feet high, with an inside diameter that ranges from 20 feet at the base to 10 feet at the top.
The tower is located approximately 3.5 miles from the Hayward-Rogers Creek Fault, which is capable of generating a magnitude 7.25 earthquake. Seismic analyses show that the tower would suffer significant damage when subject to a major seismic event, which could affect the ability of the Orinda Water Treatment Plant to obtain water from Briones Reservoir. In addition, the lower tower outlets could become blocked, preventing the reservoir from being drained. Therefore, EBMUD is working with the State Department of Water Resources (DWR) Division of Safety of Dams (DSOD) to retrofit the tower to ensure continued safe operation. The retrofit is in the design phase, with construction to follow. The California Environmental Quality Act (CEQA) process resulted in the filing of a Notice of Exemption with the Contra Costa County Clerk in January of 2019.
For after-hours, call EBMUD at 866-403-2683