Oroville Dam Safety Comprehensive Needs Assessment Summary

Oroville Dam, located on the Feather River in Butte County, is a key facility of the California State Water Project (SWP). Completed in 1967, it is owned and operated by the California Department of Water Resources (DWR). In February 2017, both the gated main spillway and the ungated emergency spillway suffered significant erosion scour damage while releasing flood waters that had flowed into Lake Oroville. Concerns for the stability of the spillway crest structures resulted in the temporary evacuation of 188,000 residents downstream of the dam. Over the next few months, flood waters were successfully managed by making controlled reservoir releases down the damaged gated main spillway through May 2017 when the gates were closed for the year and DWR began repairs to the two spillways. By the fall of 2018, the entire 3,000-foot-long chute for the gated main spillway had been completely reconstructed, and major erosion-resistant armoring had been added to the emergency spillway. The repairs resulted in making these two spillways robust structures meeting modern engineering standards.