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Posted on: October 22, 2019

New flood risk reduction and dam safety enhancements underway at New Bullards Bar

Secondary Spillway at New Bullards Bar Dam photo rendering

Yuba Water Agency is embarking on the largest project its undertaken to reduce flood risk since the building of New Bullards Bar Dam in the 1960s. 

The agency expects to fully implement three major programs and projects in the next six years, which, when fully operational, will significantly reduce this region’s flood risk and improve its climate change resilience. 

The completion of a new, approximately $160 million secondary spillway at New Bullards Bar Dam, when combined with Forecast-Informed Reservoir Operations for the Yuba and Feather rivers, and an update to the U.S. Army Corps of Engineers’ Water Control Manual for New Bullards Bar will improve the safety and operational capabilities of Yuba Water’s facilities, with a range of promising benefits. 

The documentation, permitting and design phase of the secondary spillway project is underway, with construction expected to begin at the dam in 2022. 

The new spillway gates will be 31.5 feet lower than the existing gates. When combined with improved forecasting and changes to the way water is managed at the dam with the updated Corps manual, Yuba Water will have greater flexibility and control over water releases in preparation for major storm events, ultimately creating additional room in the reservoir for the storm flows. 

Other benefits of these flood risk initiatives include: 

  • An ability to release an additional 45,000 cubic feet per second in advance of and during storm events, creating additional space in the reservoir to contain storm water runoff and snowmelt from the watershed. 

  • An ability to more accurately track, monitor and predict precipitation, snowfall and water inflow to the reservoir by several days, with special emphasis on more precise and longer-term forecasts of atmospheric rivers. This will give dam operators extra time to manage water during storm events. 

  • Enhanced dam safety with a redundant option for water releases, one that could handle the 1997 storm of record on its own.

  • Reducing the flood stage in the lower Yuba River, near the City of Marysville, by up to 3 feet during storm events as large as the 1997 flood.

  • The potential to improve water supply storage and management at the reservoir and increase carbon free hydropower generation, both critical assets in light of the impacts of climate change. 

Yuba Water Agency coordinates releases during significant storm events with the Department of Water Resources Flood Operations Center as well as its Oroville Dam Operations, the National Weather Service and the U.S. Army Corps of Engineers for public safety and in an effort to minimize impacts downstream. These new efforts will take that coordination to a much higher level.

Construction of the secondary spillway at New Bullards Bar Dam is expected to be complete in 2025. The research related to Forecast-Informed Reservoir Operations, which will result in the new operations guidelines, is underway now, with the goal to have all three initiatives complete when the secondary spillway construction wraps up.

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