Yuba County Water Agency moves forward on secondary spillway at New Bullards Bar Dam

By on June 9, 2018

A major flood in 1997 became the impetus for Yuba County Water Agency (YCWA) to identify future projects to reduce the region’s flood risk. The early January 1997 flood resulted in levee failure on the east bank of the Feather River some six miles south of Olivehurst. The affected communities of Arboga, Linda and Olivehurst saw 16,000 homes inundated in a matter of days.

Worse yet, 840 homes were flooded and three people perished. The total damage was estimated at $150 million in settlement amounts.

A series of studies, completed in 2002, resulted in a number of flood risk prevention initiatives. One project was to increase the release capacity of New Bullards Bar Reservoir by constructing a secondary spillway. A feasibility study, conducted in 2016 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 YCWA’s goals at the lowest cost with the least negative environmental impact.

The Yuba County Water Agency announced earlier this week their intention to move forward with the environmental documentation, permitting and design of a secondary spillway at New Bullards Bar Dam.

The construction of secondary spillway will increase water release capabilities in preparation for major storm events, ultimately creating additional room for inflows in the reservoir. The estimated $160 million spillway 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.”

The remaining portions of the 2016 feasibility study is slated for completion in 2021 with construction beginning in 2022. Completion of the second spillway is estimated for 2025. Completion of the new spillway and the $160 million price tag are rough estimates at this time. Both estimates will be more clearly defined as the project moves forward.

“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.

A secondary spillway at New Bullards Bar Dam would provide multiple benefits. It would provide the redundancy of an alternate for water releases in case of a problem with the primary spillway and, on its own, the secondary spillway would be able to manage releases from the reservoir in a one in 260-year storm event without exceeding the maximum pool elevation. Also, a second spillway would include a reduction in ecosystem damages from flooding as well as 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 YCWA.

Other flood risk reduction strategy by YCWA have included partnering with other local agencies on the Feather River Setback Levee and the Marysville Ring Levee. As a result of these efforts, south Yuba County and Marysville 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.

Although the costs for the field investigation, environmental documentation, permitting and design of the secondary spillway are estimated at $11 million, YCWA has been preparing financially for the costs of major infrastructure improvements, including the secondary spillway.