By Paul Moreno
Pipe segments for the South Yuba Pipe were placed by heavy-lift helicopter last week as PG&E works to replace a 240-foot section of pipe that was blown away by a winter rockfall in Nevada County. Now that the pipe is in place, crews will spend the next few weeks welding and installing collars to prepare the pipe for water delivery.
(Watch a video of a helicopter delivering a pipeline segment.)
A Type 1 heavy-lift helicopter, capable of lifting over 17,000 pounds, had been reserved for PG&E in mid-July, but was diverted to support critical firefighting needs due to increased national fire activity. Fortunately, PG&E was able to reserve another Type 1 helicopter for early August.
The South Yuba Pipe is one of two routes PG&E uses to move water from Lake Spaulding to the Nevada Irrigation District’s South Yuba Canal. The other route is via a diversion at Drum Canal to the South Yuba Canal. Since PG&E repaired the Spaulding 1 Powerhouse in July, about 60 cubic feet per second (cfs) of water have been flowing from a diversion at Drum Canal into the South Yuba Canal.
PG&E expects the South Yuba Pipe to be repaired by mid-September. In the meantime, the water company continues to ask its customers and the public to conserve water while repairs are ongoing.
During start-up testing at PG&E’s Spaulding 2 power plant, the generator sustained mechanical damage, requiring additional repairs, extending the return to service date beyond the South Yuba Pipe return to service. PG&E is currently working on a repair plan and schedule and will continue to coordinate with NID and PCWA.
Fortunately, the repair of the first of two water diversion pipes from the Spaulding 1 Power Plant in July means that a total of about 450 cubic feet per second of water is flowing into the Drum Canal. A portion of those flows, about 60 cubic feet per second, has been diverted into the South Yuba Canal below the pipe repair, which supplies the NID’s Scotts Flat Reservoir. Once the Spaulding 2 Power Plant is back online, flows of up to 100 cubic feet per second or more could flow into the South Yuba Canal, restoring full operating flow. The additional water in the South Yuba Pipe ensures that all flows from the Spaulding 1 Power Plant remain in the Drum Canal.
PG&E has informed PCWA and NID of the initial Spaulding 2 event and findings and is coordinating repair plans and schedules to minimize impacts to water deliveries.
PG&E is working with water utilities to develop a schedule for repairing the second water diversion line at the Spaulding 1 power plant, as it would require a shutdown of the Spaulding 1 power plant and limit outflow from Lake Spaulding. Once the work is completed, up to 750 cubic feet per second could flow through the power plant.
The Spaulding 2 power plant discharges into the South Yuba Pipe, which connects to the NID’s South Yuba Canal and flows to the NID’s Scotts Flat Reservoir. The Spaulding 1 power plant discharges into the Drum Canal, which flows into the NID’s Rollins Reservoir. PCWA also draws water from the Rollins Reservoir.
