Perris Dam Seismic Retrofit Enters Second Phase: Construction Begins on Outlet Tower Structure


Perris Dam Outlet Tower

The Perris Dam Tower Bridge. DWR/2019

SACRAMENTO, Calif.Today, the California Department of Water Resources (DWR) started construction on the Outlet Tower Bridge, a component of the Perris Dam Complex in Riverside County. The work is part of DWR’s statewide effort to reduce seismic risk to State Water Project (SWP) dams.

“This project is an example of DWR’s ongoing commitment to modernize California's water infrastructure to better protect California’s water supplies and enhance public safety,” said Ted Craddock, Acting SWP Deputy Director. “Earthquakes are a constant threat to our infrastructure, and we need to make our facilities as resilient as possible.”

The bridge work is part of the Outlet Tower Improvements Project, the second of three Perris Dam seismic retrofit projects. Located just upstream of the Perris Dam south abutment and connecting the Outlet Tower to the shoreline, the bridge provides access to the Outlet Tower for operation of the control valves and fish screens.

The retrofit of the Tower Bridge consists of modifications to the bridge support, bridge seat, end diaphragm, and installation of stiffener plates. The work that is planned for completion fall of 2020 will ensure the tower bridge can withstand a major earthquake and ensure access to valve controls for release of water under normal and emergency operations.

Future work on the Outlet Tower and the downstream water release and delivery facilities include the construction of a new control building, installation of a new gate, installation of seismic and security monitoring equipment, repair of penstock liner and refurbishment of slide gate and cylinder, and installation of new hydraulic power units.

The third and final project at Perris Dam will focus on the Emergency Release Facility (ERF) and is planned for completion in 2023. The ERF project provides improvements downstream of the reservoir that would direct the flow of water in an emergency requiring the dewatering of the reservoir. Flows would be directed through a series of berms and lined and unlined channels that would ultimately terminate at the Riverside County Flood Control and Water Conservation District’s Perris Valley Channel.


Constructed from 1970 to 1974, Perris Dam was identified as a high priority state-owned dam due to its proximity to nearby earthquake faults and large downstream communities. The seismic retrofit to Perris Dam began in 2005 to improve seismic stability and enhance public safety at the Perris complex. Completed in 2018, the first project included several upgrades, such as strengthening the foundation and adding 1.4 million-cubic-yards of embankment material at the 130-foot tall, earthen Perris Dam. Following completion of that work, DWR began a controlled refilling of the reservoir in March 2018. 


Lake Perris is the State Water Project’s southernmost facility and the terminal storage facility on the East Branch.


For information about the remediation projects, visit our Lake Perris and Perris Dam Projects website.

Additional Resources: Photos  





Maggie Macias, Information Officer, Public Affairs, Department of Water Resources

(916) 653-8743 |