By rosebell
In order to upgrading key components of its hydropower generation infrastructure in the Yuba County foothills, Yuba County-based public entity Yuba Water Agency has granted a $76.8m contract.
Being delivered to a joint venture of Obayashi and Drill Tech Drilling & Shoring, this contract’s project focuses on the Colgate tunnel outage and is slated to start in fall 2025.
The intention of this tunnel outage will be a four-mile-long rock tunnel and a one-mile-long penstock pipe.
The responsibility of carrying water from New Bullards Bar Reservoir to New Colgate Powerhouse, located at the base of Lake Francis Road in Dobbins, is up to these components.
Removing rocks and debris, repairing and reinforcing worn parts, as well as installing a new protective valve system at the top of the penstock pipe, will be done by Yuba Water during the outage.
According to Yuba Water Agency, the upgraded valve will improve downstream infrastructure protection and allow easier maintenance without needing to dewater the entire tunnel.
According to Yuba Water hydro engineer Casey Peterson: “Even though recent inspections show the tunnel is in good condition, this project will reinforce key areas to help prevent future unplanned outages and ensure reliable operations for decades to come.”
The date of planning for the tunnel outage by Yuba Water was since 2017, while conducting remote inspections of the tunnel system and working with contractors and manufacturers to design and fabricate specialised parts.
With the aim of securing three 14ft diameter, 11 tonnes connectors, called flanges, which will be installed as part of the new protective valve, the public agency worked for more than one year.
The scheduled date for commencing staging of the project is September 2025, whereas the major work will start from October to January 2026. During this period, Colgate’s hydropower generation units is due to be offline.
Yuba Water is funding these essential improvements through hydropower revenue and state grant funds.
In December last year, Yuba Water committed over $2.9m to improve water delivery reliability for Yuba County farmers by lining several miles of canals in the Hallwood Irrigation Company’s service area.
