Oroville Dam Transmission Line Reroute
Owner: California Dept. of Water Resources
Lead Design/Civil/Structural Firm: Stantec Inc.
General Contractor: Barnard Construction Co.
Following the February 2017 spillway failure at Oroville Dam, the California Dept. of Water Resources needed immediate assistance to perform critical emergency work on the Oroville-Table Mountain 230-kV transmission lines that spanned the spillway. Emergency contractor Stantec brought in Barnard Construction, whose main goal was to construct shoofly circuits to allow power generation at the base of the dam.
“We sat down on a Friday afternoon, looked at some news stories about the failure and had a quick call with the engineer,” says Alex Raby, project manager at Barnard Construction. “It went from an idea on Friday to crews ready to work on Monday.”
Barnard initially removed conductor for two circuits and towers on the lower line that the eroding spillway was close to undermining. With the conductor removed, crews quickly strung in new conductor on upper existing lattice towers to allow the Oroville Dam Hyatt Power Plant to resume operations.
Installation of the circuit gave Stantec time to design an emergency shoofly while Barnard procured shoofly poles, conductor and hardware. With a design in place, Barnard crews installed tandem single-circuit shoofly lines, composed of eight H-structures per circuit, spanning 7,500 linear ft. The shoofly moved the lines away from the potential hazards of the failing spillway and allowed DWR’s other contractors to complete the emergency spillway repairs.
For a permanent solution, Barnard installed two double-circuit lattice lines that rerouted the alignment to the opposite side of the river, away from hazards associated with the spillway and recovery work. Line construction required installation of 22 double-circuit lattice towers and 28,000 circuit ft of conductor. The team finished all work in less than six months.
The project site was on a steep, heavily vegetated canyon divided by the Feather River.
The high number of contractors working in a limited space required an increased focus on safety. The safety manager and other management attended daily meetings hosted by CalFire to receive updates. Each morning Barnard updated crews and subcontractors about the day’s activities including regular helicopter operations.