Testing underway for new Folsom Dam Auxiliary Spillway Prior to Final Commissioning

Testing began recently by the U.S. Bureau of Reclamation and the U.S. Army Corps of Engineers at the new Folsom Dam Auxiliary Spillway as part of the official commissioning of the newly constructed structure. The tests began this past week and will extend through next week as well. They operating and releasing water from all six new auxiliary spillway radial gates.

Reclamation, the Corps, the Sacramento Area Flood Control Agency, the California Department of Water Resources, and the Central Valley Flood Protection Board formed an unprecedented partnership more than ten years ago to provide enhanced flood protection for the Sacramento area. The area is one of the most at-risk communities in the nation and the unprecedented partnership is known as the Joint Federal Project (JFP). The JFP’s new auxiliary spillway was constructed adjacent to the main concrete dam and it is the key feature to improving Folsom facility’s flood risk management.

According to Reclamation, the new auxiliary spillway includes a 1,000-foot-long approach channel beginning in Folsom Reservoir, a concrete control structure with six bulkhead and six radial gates, a 2,100-foot-long auxiliary spillway chute, and a stilling basin that will act as an energy dissipation structure as water discharges and enters the American River. The Corps, in cooperation with Reclamation, are testing all of the major systems in the structure, ensuring that the facility operates as intended in the design.

Reclamation has been able to safely operate Folsom Dam and its Reservoir for water supply, power generation, fish and wildlife mitigation and enhancement and other required purposes during the JFP construction.

Once fully commissioned later this year, the new facility will be better able to manage large floods by safely releasing more water from Folsom Reservoir earlier during a storm through both the spillway gates on Folsom Dam. The dam sits at an elevation of 418 feet while the new control structure’s radial gates sit 50 feet lower in the reservoir at elevation 368 feet. This will reduce hydrologic risk and leave more storage capacity in the reservoir.

Folsom Dam and Reservoir is a component of Reclamation’s Central Valley Project, and is operated by its Mid-Pacific Region’s Central California Area Office. Reclamation and the Corps have multiple authorized projects at Folsom Dam and its related structures.