Major flood risk reduction and dam safety enhancements planned for New Bullards Bar

Major flood risk reduction and dam safety enhancements planned for New Bullards Bar

A significant reduction in flood risk and enhancements to dam safety are in the works for Yuba County.

Yuba County Water Agency today approved moving forward with the environmental documentation, permitting and design of a secondary spillway at New Bullards Bar Dam.

The construction of an estimated $160 million secondary spillway will increase water release capabilities in preparation for major storm events, ultimately creating additional room for inflows in the reservoir.  This will decrease flood risk downstream, including the areas of Marysville, Linda, Olivehurst, Plumas Lake and Yuba City.

“New Bullards Bar Dam is already in great shape,” said Yuba County Water Agency General Manager Curt Aikens. “This enhancement will help even more. Especially after Oroville, we know more than ever how important it is to have redundancy with a secondary option for releases in case of an emergency.”

As a result of the major flood in 1997, Yuba County Water Agency initiated a series of studies, completed in 2002, to identify future projects to reduce the region’s flood risk. One such project was a plan to increase the release capability of New Bullards Bar Reservoir by constructing a secondary spillway.

The feasibility study, conducted in 2016, considered various alternatives and determined a secondary spillway, with the lowest water release point 31.5 feet lower than the existing spillway, to be the best option to accomplish the agency’s goals at the lowest cost with the least negative environmental impact.

This phase of the project is estimated to wrap up in 2021, with construction beginning in 2022. It is estimated to take approximately three years to build. Both the cost and schedule are rough estimates at this time, expected to be much more clearly defined as the project is further designed.

An additional benefit of the secondary spillway is the redundancy of an alternate for water releases in case of a problem with the primary spillway. The secondary spillway would, on its own, be able to manage releases from the reservoir in a 1 in 260 year storm event without exceeding the maximum pool elevation.

“With the combination of a secondary spillway and planned alterations to the way water is managed at the dam, the flood stage reduction in Marysville could be reduced by about 2 feet during a 1997-type storm,” said Naser Bateni, senior vice president of GEI Consultants.

Additional benefits of the secondary spillway include a reduction in ecosystem damages from flooding, enhanced overall flood system flexibility and resiliency.

“This great reduction in our flood risk also benefits the entire region – reducing risk all the way to the Delta,” said Brent Hastey, chairman of the Yuba County Water Agency.

These enhancements are just one part of the agency’s overall strategy to significantly reduce flood risk in the region. Other efforts have included partnering with other local agencies on the Feather River Setback Levee and the Marysville Ring Levee, among others. As a result of these efforts, the south Yuba County and Marysville areas are slated to become one of the first regions in California to reach the state’s requirement for 200-year levee certification in urban areas.

The agency has been preparing financially, saving to help pay for the costs of major infrastructure improvements, including the secondary spillway.

Costs for the field investigation, environmental documentation, permitting and design of the secondary spillway are estimated at $11 million.