The California Department of Water Resources (DWR) has completed a $235 million rehabilitation of the river valve outlet system (RVOS) at Oroville Dam, strengthening the facility’s operational reliability and its ability to support downstream flood protection and aquatic habitat.

The RVOS is located within one of the dam’s original diversion tunnels and allows DWR to release cold water from deeper portions of Lake Oroville into the Feather River. During periods of extreme heat and drought, these releases can help maintain suitable water temperatures for fish populations, including Chinook salmon and steelhead trout.

The project also supports Oroville Dam’s role within California’s State Water Project. The 770-foot-tall dam provides flood protection, water supply and hydropower while supporting habitat in the Feather River.

Construction began in October 2022 and required work in the confined space at the base of the dam while maintaining the facility’s water management and power generation functions. Construction activities included transporting valves and equipment by barge and installing temporary bulkheads to allow work on the valve infrastructure.

DWR completed commissioning of the rehabilitated valve system in June. The agency said the project is part of its broader investment in aging State Water Project infrastructure to maintain reliable operations under changing climate conditions.