DWR Completes Major Rehabilitation of Oroville Dam's River Valve Outlet System

Infrastructure Upgrades Ensure Ongoing Reliability and Access to Cold Water

The California Department of Water Resources (DWR) announced today the completion of a $235 million project to rehabilitate Oroville Dam's river valve outlet system (RVOS), ensuring the continued operation of a critical feature of the dam for decades to come. This upgrade improves operational reliability, protects fish populations, and strengthens the State Water Project's resilience to climate-driven extreme heat and drought.

Oroville Dam, the tallest dam in the United States at 770 feet, is a cornerstone of the State Water Project, providing flood protection to downstream communities, water supply, clean energy generation, and recreation while supporting Feather River habitat for endangered and threatened fish species. Constructed between 1961 and 1967, the earthen dam towers over the northern Sacramento Valley.

The RVOS is located deep within one of the dam's early diversion tunnels and allows DWR to release cold water from the deeper portions of Lake Oroville into the Feather River. That capability is especially important during periods of extreme heat and drought, when colder releases can help reduce downstream water temperatures and support fish populations.

"This investment in Oroville Dam's infrastructure ensures the reliable and safe operation of the State Water Project's largest flood protection and water supply facility," said John Yarbrough, Deputy Director of DWR's State Water Project. "DWR will continue to prioritize modernization projects to improve aging infrastructure in an ever-changing climate."

California summers are becoming hotter as climate patterns shift and prolonged droughts can significantly reduce available water supplies. During extended dry periods, when Lake Oroville's water storage drops, frigid water released from the bottom of the reservoir helps support fish populations in the Feather River and at the Feather River Fish Hatchery. DWR carefully monitors water temperatures to maintain suitable conditions for fish and meet environmental regulations.

"Part of DWR's mission is to operate State Water Project facilities to protect, restore, and enhance the natural environment," Yarbrough said. "This includes operating the Oroville-Thermalito Complex facilities in a way that supports Central Valley fish populations including Chinook salmon and steelhead trout, which spawn each year in the Feather River below the dam."

Construction on the RVOS project started in October 2022, with a large multidisciplinary team overseeing several construction contracts. The project's location deep at the base of Oroville Dam also required creative construction management.

"Rehabilitating the RVOS was highly complex," said Jason Brabec, DWR principal engineer and project manager. "It required immense coordination with contractors in a small space, all while ensuring that Hyatt Powerplant met its green energy commitments and cold-water release requirements. The years-long project required barges to transport valves, materials, and equipment, the installation of temporary bulkheads to permit work on valve infrastructure, and other creative construction methods. Because this system is critical to Oroville Dam's operations, all phases of the work required high construction standards and safety protocols."

Construction firms Syblon Reid of Folsom and The Dutra Group of San Rafael formed a joint venture to complete this major infrastructure rehabilitation project. Commissioning of the valve system was completed in June.

Completion of the RVOS rehabilitation is part of DWR's ongoing investment in Oroville Dam and other State Water Project facilities to ensure they continue to reliably serve California's people and environment for decades to come. To learn more about the State Water Project, visit DWR's website.

Additional Media Resources:
• Pixel Photo Gallery featuring images throughout construction
• VIDEO: Oroville Dam's River Valve Outlet System Rehabilitation Project

Contact:
Raquel Borrayo, Public Affairs, Department of Water Resources

[email protected]