Perris Dam Modernization Project

Perris Dam, located in Riverside County about 60 miles east of Los Angeles, provides water supply for recreation, fish and wildlife enhancements, and millions of Californians.  Lake Perris is the terminal storage facility for the State Water Project. It is located at the terminus of the East Branch of the California Aqueduct. The dam was constructed from 1970 to 1974 by the California Department of Water Resources (DWR).

Earthquakes pose some of the highest risks to dams in California. Since the late 1990s, DWR’s Division of Safety of Dams has conducted in-depth investigations and re-evaluations of dams located near seismic faults. Over the past 20 years, dam owners throughout California have spent approximately $1.5 billion on seismic improvements to dams.

Perris Dam was identified as a high priority state-owned dam for seismic improvements due to its proximity to nearby earthquake faults and large downstream communities.

The Perris Dam Modernization Project addresses seismic risks that could impact water deliveries and the safety of surrounding communities. In 2005, DWR began the Perris Dam Modernization Project with the seismic retrofit to the dam embankment. With the completion of the remaining project components in 2026, DWR will achieve its goal of upgrading its infrastructure to protect our water system and enhance public safety.

The Perris Dam Modernization Project includes three projects: the Perris Dam Remediation Project, the Outlet Tower Improvements Project, and the Emergency Release Facility Project.

Perris Dam Remediation Project

The Perris Dam Remediation Project, the first of the three Perris Dam seismic retrofit projects, was completed in April 2018. It included several upgrades, such as strengthening the dam’s foundation with over 320,000 cubic yards of cement deep soil mixing (CDSM) and adding 1.4 million-cubic-yards of embankment material to buttress the downstream of the 130-foot tall, earthen Perris Dam.

Following completion of the work, DWR began a controlled refilling of the reservoir in March 2018. The refilling was completed in July 2019.

Outlet Tower Improvements Project

The Outlet Tower Improvements Project, part of the Perris Dam seismic retrofit projects, includes the tower bridge seismic retrofit project, and the Outlet Works Modification project. This project will ensure safe and reliable release of water during normal and emergency operations. The Outlet Tower Improvements Project is planned for completion by 2026. Completed work to date for the project includes:

The tower gantry crane and fish screens repair were completed in 2018 and included upgrading the mechanical and electrical components for the crane controls and operating systems. The fish screens were removed, cleaned, and repaired for corrosion damage. 

The tower bridge seismic retrofit project, completed in 2020, consisted of modifications to the bridge supports and bridge seats of the tower bridge that provides access to the tower for normal and emergency release operations.

The tower penstock liner repair, finished in 2021, included penstock improvements after an inspection for leaks, cracks, and coating and corrosion damages.

Future work planned for the outlet tower and the downstream release and delivery facilities includes the installation of a new automated flow control gate, hydraulic controls equipment, seismic and security monitoring equipment, and the construction of a control building and an energy dissipation structure.

Emergency Release Facility Project

Perris Dam and the surrounding area map shows the project overview for the Emergency Release Facility.

The Emergency Release Facility (ERF) Project, with construction planned from 2023 to 2026, will safely route the flow of water in an emergency that requires the rapid lowering of Lake Perris. The project will provide protection from a 100-year flood and a major earthquake failure to the community and more than 6,000 residents. Flows would be directed by levees into a channel that would ultimately flow into the Perris Valley Storm Drain.  

The project’s improvements will protect a local school, Interstate 215, and a water treatment plant. The project includes community infrastructure improvements like new levees, bridges, a local drainage system, and improved roadside landscaping and relocation of utilities. Over 100 meetings have been held with the community, county, city, utility companies, and fairgrounds since 2013 to discuss this project and the impacts of its construction.

What to Expect

The Perris ERF project is expected to include:

• Temporary impacts to traffic during the construction. The stage construction and traffic handling plans were designed to minimize impact to vehicular, pedestrian, and bicyclist travel through the project site.
• Temporary traffic modifications will be made at Evans Road, Lake Perris Drive, and Fair Way during construction. All existing through lanes on Ramona Expressway will be maintained during construction.
• DWR will make sure that there is access in and out of the fairgrounds during the construction. The bridge construction will require traffic adjustments at Evans Road and Lake Perris Drive. While Evans Road bridge is under construction, the project will maintain a minimum of one through lane in each direction on Evans Road. During the construction of a proposed new bridge at Lake Perris Drive, DWR will shift Lake Perris Drive to a new temporary intersection for traffic and access to Lake Perris and the fairgrounds.

• Fair Way will be closed during the construction of the Fair Way culvert, and access to the fairgrounds will be through the gates along Lake Perris Drive. The construction at Fair Way will not impact Avalon Parkway.   
• A new parking area will be available directly across from the Fairgrounds to replace the parking area used for construction. There will be sufficient parking for the fairground events and its tenants.
• When construction activity is in progress, some localized noise, dust, and increased traffic may be expected.
• Access to the southeast side of the Lake Perris State Recreation Area and to the Lake Perris Fairgrounds will be maintained.

For the latest updates about recreational opportunities, contact the California Department of Parks and Recreation at 951-940-5600 or visit the CA Parks website.

Environmental Documents
DWR has prepared the following environmental documents in support of the projects described above.

• NOD for Perris Dam Emergency Release Facility EIR - May 2018
• Final DWR Perris Dam Emergency Release Facility - Environmental Impact Report - February 2018
• Appendix AA - Draft DWR Perris Dam Emergency Release Facility - Environmental Impact Report - September 2016
• Appendix AB - Recirculated Draft DWR Perris Dam Emergency Release Facility - Environmental Impact Report - September 2017
• NOD for Perris Dam Emergency Release Facility EIR Addendum #1 - September 2020
• Final Perris Dam Emergency Release Facility EIR Addendum #1 - September 2020
• NOE for SCE Minor Transmission/Distribution Relocation Project - DWR Perris Emergency Release Facility - May 2020
• NOD for Perris Dam Emergency Release Facility EIR Addendum #2 - December 2022
• Final Perris Dam Emergency Release Facility EIR Addendum #2 - December 2022