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MARYSVILLE, Calif. (July 24, 2020) – Yuba Water Agency’s Board of Directors Thursday authorized staff to move forward with a new design of an estimated $225 million secondary spillway at New Bullards Bar Dam, marking an important step forward for the agency’s largest project to reduce flood risk since the dam was built.
The board had previously approved a tunnel design for the secondary spillway, however, during the detailed design work, it became clear that an alternative, open-channel design would be more effective in terms of public safety, cost and overall environmental impact.
The secondary spillway is one piece of a three-part initiative that will significantly reduce flood risk and improve public safety in Yuba County and nearby communities. The effort includes the development of 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, which guides flood operations for the dam. Together, the trio of projects will allow Yuba Water to better predict large, threatening storms and release water from New Bullards Bar before dangerous weather hits, while there is still plenty of capacity downstream.
“Each high water event stresses our levees,” said Yuba Water General Manager Willie Whittlesey. “But by evacuating water sooner, we can reduce the time that the water is high on the levees, which makes the entire levee system more resilient long term.”
The improved control of water releases is expected to reduce water levels around levees near Marysville by up to two feet during a storm like the 1997 New Year’s Flood, the largest on record. This will decrease pressure on levees throughout the region, thereby reducing risk to thousands of lives and billions of dollars of property and assets in Yuba and Sutter counties.
The new plan approved by the board changes the concept from a tunnel design to an open spillway design. The gates will still be 31.5 feet lower than the existing spillway gates, which will allow for the early release of up to 35,000 cubic feet of water per second, before storms arrive, while the river channel can handle the flows. The current spillway is too high in the dam to release water until after a storm has arrived and begun filling up channels downstream.
The proposed secondary spillway would also be able to handle a storm like the 1997 flood on its own, providing an alternative release option for enhanced dam safety.
The board’s decision followed a review and discussion of several alternative designs and a detailed cost-benefit analysis of the work, which found the $225 million cost of the secondary spillway to be far less than the calculated $353 to $406 million in economic benefits the project is projected to provide.
Yuba Water will finalize 60 percent of the secondary spillway design and develop a coordinated cost-share funding strategy before returning to the board with an update in 2021.
Also during Thursday’s special meeting, the board heard an update on the county-wide economic development initiative, which was developed with extensive stakeholder input. The agency’s Economic Development Strategic Plan includes four focus areas: infrastructure expansion; education and workforce development; tourism and visitor services; and technology clusters.
“All of our efforts to improve economic development in the region would be stopped in their tracks if we had another devastating flood,” said Yuba Water Director Doug Lofton. “So, we absolutely need to make this investment in the secondary spillway to protect our future.”