DWR Begins Construction on Seismic Retrofit Second Phase at Perris Dam

By on October 8, 2019
Department of Water Resources

The Department of Water Resources (DWR) began construction on the Outlet Tower Bridge, a component of the Perris Dam Complex in Riverside County, earlier this week. The bridge work is part of the Outlet Tower Improvements Project, the second of three Perris Dam seismic retrofit projects.

“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 retrofit of the Tower Bridge consists of modifications to the bridge support, bridge seat, end diaphragm, and installation of stiffener plates. The work is part of DWR’s statewide ongoing effort to reduce seismic risk to State Water Project (SWP) dams.

Perris Dam, located in Riverside County, was constructed between 1970 and 1974. It was identified as a high priority state-owned dam for retrofit due to its proximity to nearby earthquake faults and large downstream communities. The first phase of the Perris Dam seismic retrofit began in 2005 to improve seismic stability and enhance public safety at the Perris complex.

The bridge work is part of the Outlet Tower Improvements Project and is 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 Tower Bridge retrofit will include modifications to the bridge support, bridge seat, end diaphragm, and installation of stiffener plates. The work, planned for completion fall of 202,0 will ensure the tower bridge can withstand a major earthquake and ensure access to valve controls for release of water under both normal and emergency operations.

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

The last phase at the Riverside County dam third and final project is planned for completion in 2023. The Perris Dam Emergency Release Facility (ERF) project will provide 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, as well as lined and unlined channels, that would ultimately terminate at the Riverside County Flood Control and Water Conservation District’s Perris Valley Channel.