PG&E Working Around the Clock to Restore Powerhouse so Flows to Water Agencies Can Resume

By Paul Moreno

During a storm in February, a rockslide damaged more than 200 feet of PG&E’s South Yuba Pipe, which connects to Nevada Irrigation District’s (NID) South Yuba Canal. The pipe is one of two avenues PG&E has to deliver water from the Spaulding Reservoir to NID and the Placer County Water Agency (PCWA). 

Snow and the potential for more slides on the wet hillside had prevented PG&E from fully accessing the hillside until mid-April so PG&E’s geosciences team and specialists could further evaluate the slide. Crews are now stabilizing the rockslide by removing loose and potentially unstable material, with debris removal to follow. Afterward pipe foundations can be repaired, and new pipe installed.

In early March during an inspection, PG&E discovered a leak inside its Spaulding 1 powerhouse, which discharges water into the Drum Canal. Flows from Drum Canal can be diverted to the South Yuba Canal. The powerhouse had to be shut down so PG&E could dewater a tunnel and inspect the leak, which came from the discharge horns (which are discharge pipes with a 90-degree bend). With the powerhouse off-line for repair work and the South Yuba Pipe currently inoperable due to the rockslide, water is not being released into the South Yuba Canal or Drum Canal.

“We well understand the water needs of NID and PCWA, which is why we made the repair work a top priority and are doing everything we can to restore flows as quickly and safely as possible,” said Joe Wilson, vice president of PG&E’s North Valley & Sierra Region. “Crews and contractors are working around the clock, with as many people working inside the powerhouse who can safely and efficiently work there at the same time.”

PG&E dewatered the tunnel and began removing cladding from the discharge horns embedded in concrete. While PG&E initially estimated the powerhouse could be returned to service as of April 30, further analysis of the extent of repairs needed indicates that the restoration date most likely will be sometime in mid-June.  As more material was removed, PG&E determined that replacing both discharge horns required additional time because there is only room inside the powerhouse to work on one discharge horn at a time.

PG&E coordinated with NID and PCWA on pursuing an option to resume flows after the first discharge horn was replaced so partial flows could start about mid-June. The second discharge horn could be replaced at a time of the year when the agencies’ need for water is far less and the powerhouse could again be taken offline to finish the work. Both agencies support this option and, once the first horn is repaired, flows of about 400 cubic feet per second (cfs) can be delivered. 

This would allow for about half of the deliveries to resume in the Drum Canal with a portion of that able to be diverted over to the South Yuba Canal around the landslide. The South Yuba Pipe is expected to be repaired in late summer or early fall.

After the second horn is replaced, normal flow operations from the Spaulding 1 powerhouse resume.