Perris Dam Remediation Project

In April 2018, DWR completed a major retrofit to Perris Dam in Riverside County as part of a statewide effort to reduce seismic risks to dams.

Upgrades to the 130-foot tall, earthen dam included strengthening roughly 800,000 cubic yards of foundation material by mixing cement with soil and reinforcing it with a 1.4 million-cubic-yard earthen stability berm placed on the downstream side of the dam. The dam upgrades were designed to withstand a major earthquake.

 

Perris Dam, constructed from 1970 to 1974, was identified as a high priority state-owned dam due to its proximity to nearby faults and large downstream communities.

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.

The dam remediation is one of three major projects to improve seismic stability and enhance public safety in the Perris Dam Remediation Program. Other projects include:

 

• Outlet Tower Improvements, with completion planned for 2021
• Emergency Release Facility (ERF) Project, with completion planned for 2023
  • 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

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. The Outlet Tower and ERF projects enhance the safety of the dam for other risks in addition to that posed by earthquakes.