An aerial view shows high water conditions at Oroville Dam at Lake Oroville in Butte County, California. On this date, the water storage was 3,524,311 acre-feet (AF), 100 percent of the total capacity. Photo taken June 12, 2023. Ken James / DWR

DWR NEWS: Maintenance Work on Oroville Main Spillway Set to Begin

From the Department of Water Resources:

Starting this week, Oroville-area residents will notice construction staging equipment and materials at Oroville Dam’s main spillway. The Department of Water Resources (DWR) is performing minor routine concrete and sealant repair work on localized areas of the spillway identified during annual inspections.

While the main spillway continues to perform well and operate as designed, periodic concrete and sealant repairs of the spillway are expected due to seasonal temperature variations, spillway releases, and sun exposure.  In 2023, Oroville Dam’s main spillway has passed over 2,370,000 acre-feet of water – approximately 67 percent of the capacity of Lake Oroville – with flows up to 36,000 cubic feet per second this spring.

Construction work is expected to continue through November 15, but is dependent on weather and Oroville Dam operations. DWR will be monitoring reservoir levels and weather forecasts closely and will complete repair work early if spillway releases are required for flood control. The construction contract period extends through 2025, permitting the contractor to complete repairs in future dry seasons should the 2023 construction window be limited.

Approximately 500 square-feet of total concrete repairs are anticipated, representing less than 0.1 percent of the spillway’s surface. DWR will also be replacing joint sealant at select chute slab and wall joints that wear over time due to the spillway’s environment, and inspecting 51,000 feet of piping that supports the spillway’s improved drainage system.

The spillway was rebuilt to the highest engineering and safety standards with oversight and guidance by the Federal Energy Regulatory Commission (FERC), Division of Safety of Dams (DSOD), and an independent board of consultants. DWR performed a significant amount of inspection and testing throughout construction to verify compliance with project specifications. DWR also provides regular updates to the Oroville Dam Citizens Advisory Commission, a public forum for discussing operations, maintenance, and public safety activities at Oroville Dam and its facilities.

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