- Location: Oroville, California
- Owner: California Department of Water Resources (DWR)
- Engineer(s): Stantec Engineering
- Contract Type: Not to Exceed
- Status: Completed
Photo 1 credit: Ryan McKinney / California Department of Water Resources
Photo 2 credit: Florence Low / California Department of Water Resources
Photo 3 credit: Kelly M. Grow/ California Department of Water Resources
Barnard’s Electric Transmission Group assisted the California DWR as DWR addressed several key issues that arose when failure of the main spillway and erosion at the head of Oroville Dam’s auxiliary spillway raised concerns that spillway failure could cause uncontrolled releases of water from Lake Oroville. DWR contracted with our Barnard team to address two existing double-circuit 230kV lines that traversed the Oroville Dam. The erosion of the spillway put the lower line in jeopardy.
In response to the critical nature of the work, Barnard had a team onsite one day after initial contact with DWR and its Design Engineer Stantec. Our equipment arrived within three days and many key materials arrived within one week. Our team’s first step was to isolate a compromised structure threatened with collapse. Crews began by removing the conductor from the circuits on the lower line of this tower. This isolated the structure closest to the erosion so that if the spillway failed and the tower was knocked out, the other towers would remain standing. Dropping the circuit forced the hydroelectric power generation to be shut down, stopping the water flow from the base of the dam. This increased the strain on the failing spillway, which made completing the next steps expeditiously all the more important.
The team then installed a second circuit on an upper line that had only one circuit in place to allow hydropower generation to resume. Barnard subcontracted Siller Helicopters to use a Skycrane for removal of the threatened tower. Barnard, working with Stantec, installed a Temporary Shoofly arrangement until a new permanent line and alignment could be designed and approved. The design for the two Temporary Shoofly single-circuit lines places the critical lines higher on the dam and further from erosion. Each of the two Temporary Shoofly lines included 8 pole structures, 1.5 circuit miles of 1113kcmil, 5 tangent structures, 3 deadends, 2 static lines, 15 wood poles, and 4 steel poles. This project also included construction of roads and crane pads, auger holes for shoofly pole placement, right-of-way clearing, and guy anchor installation.
Subcontractor Outback was able to begin excavation of the auger holes while Barnard procured wood and steel poles, crossarms, conductor and line hardware. Line work continues. Teamwork onsite included daily coordination with myriad other key activities occurring on the dam and constant coordination with Stantec to solve problems and complete the work on an expedited schedule.