PYRAMID DAM MODERNIZATION

PYRAMID DAM AND LAKE are located about 60 miles northwest of Los Angeles and provides water storage for the greater LA area. The dam was built between 1969 and 1973 as part CALIFORNIA STATE of the California Department of Water Resources (DWR) State Water Project (SWP). WATER PROJECT DWR is modernizing its SWP portfolio across the state. This includes identifying and proactively addressing any issues that could impact the delivery of water or the safety of surrounding Begun in earnest in the communities. Over the next several years, DWR will conduct assessments of the dam and 1950s, the California State undertake construction activities to ensure the dam continues to function safely. Water Project (SWP) is a water storage and delivery system that supplies water to Status of Pyramid Dam Spillway Condition more than 27 million people and Extreme Weather In its most recent inspection, the California and provides irrigation for Division of Safety of Dams (DSOD) rated n The gated spillway at Pyramid Dam is about 750,000 acres of Pyramid Dam as satisfactory – meaning used approximately once per year to farmland. The SWP spans there are no existing or potential dam safety release natural inflows and whenever two-thirds of the length of deficiencies that will impact the functioning of inflows exceed stream release capacity California and includes 26 dams and reservoirs; 705 the dam; however, there are improvements n The emergency spillway at Pyramid dam miles of canals, tunnels, that could be made to mitigate impacts due has never been used. to an extreme weather event or earthquake. and pipelines; and nine n Climate models show that increased Based on the most recent DSOD findings hydroelectric power plants. temperatures in California will result in as well as other inspection and assessment In addition to water supply, more precipitation falling as rain instead activities conducted by DWR, the initial focus the SWP provides many of snow which will change river flows in of the Pyramid Dam modernization will be to benefits, including flood the state and could impact how DWR assess the impacts of an extreme weather control, power generation, operates the SWP facilities to manage event and to conduct earthquake analyses to recreation, and fish and changing precipitation patterns. identify improvements for the gated spillway wildlife habitat. and the emergency spillway. n DWR wants to ensure that the gated spillway will continue to work and that the The SWP collects rainfall and emergency spillway will work appropriately snowmelt runoff, transports if some future events require its use. the water through facilities like the California Aqueduct, Earthquake Resiliency and stores water in one of the many storage facilities, n  In 2019, DWR complete an analysis of the like Pyramid Lake. The SWP expected performance of the intake towers works as a system to manage (the structures that are used release water supply throughout the water from the reservoir) in the event of SWP, which can vary both an earthquake. Damage to the towers seasonally and from year to during an earthquake would not cause the year, to provide water to the dam to fail, however it would significantly 29 local water agencies that reduce DWR’s ability to release water, in turn deliver the water to slowing/reducing the delivery of water to their customers. customers. If this occurred during peak PYRAMID DAM MODERNIZATION

water inflow to the reservoir (typically late winter and early spring) the reduced ability to release water could raise reservoir levels too much, and DWR would potentially have to use the spillway to release water and lower water to a safe level. n DWR is also conducting seismic evaluations of the gated and emergency spillways to determine if any retrofits are necessary to ensure they will work appropriately in the event of an earthquake. DWR expects the evaluations to be completed in 2022. What to Expect? Top: Pyramid Dam and Lake located near Piru Creek During the modernization process, DWR will in Los Angeles County. (DWR photography) be operating construction equipment which will Middle: Gated spillway and outlet works discharging result in some localized noise and increased water. (2019 DWR Southern Field Division photography) activity may be expected. Bottom: Angeles Tunnel Intake Structure near DWR anticipates that the modernization of the Pyramid Dam during construction. The tunnel conveys water from Pyramid Lake to Castaic Lake. dam will take about 10 years to complete. (DWR photography) For more information, please contact [email protected]