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Posted on: September 25, 2018

Exploratory drilling at New Bullards Bar Dam set to begin

Water being released down New Bullards Bar Dam's spillway.

Beginning Monday, Sept. 24, people traveling across New Bullards Bar Dam and recreating on the reservoir will see heavy machinery mobilizing in the parking lot on the east side of the dam, in preparation for exploratory work related to Yuba Water Agency’s plans to design and build a $160 million secondary spillway at the dam.

Large drills will be positioned on both the water and downstream sides of the reservoir to obtain samples to determine the strength of the underlying rock, ultimately influencing how the planned spillway tunnel and foundation will be designed.

Traffic is not expected to be impacted, but caution is advised when traveling across the dam as large trucks and machinery may occasionally be entering the roadway. No major impacts are expected for those recreating on the reservoir.

“New Bullards Bar Dam is in great shape and this exploratory drilling is not to address any safety concerns,” said Yuba Water Agency General Manager Curt Aikens. “Obtaining core rock samples is one of the first steps in designing the secondary spillway, a project that will significantly reduce flood risk in the region and enhance the dam’s safety, as well.”

This phase of the project is estimated to take up to a few months.

The planned secondary spillway will reduce flood risk by having gates lower on the dam, making it possible for Yuba Water Agency to release more water from the reservoir before large, threatening storms, when there is enough downstream channel capacity to handle the flows. That will free up space in the reservoir to hold back the peak of the flows when the storm arrives. Additionally, having an alternative spillway enhances dam safety by ensuring the ability to release water in case of a problem with the primary spillway.

The permitting and design phase is estimated to wrap up in 2021, with construction beginning in 2022.