NEVADA CITY, Calif. March 25, 2024 – The outage at PG&E’s Spaulding #1 powerhouse, first reported by us on March 9th, was described by PG&E as follows: “During a routine inspection at PG&E’s Spaulding 1 powerhouse on March 6, a leak was discovered adjacent to a pressure relief valve.” A search of public documents on the Federal Energy Regulatory Commission (FERC) website shows the pressure relief valve being flagged by FERC during a dam safety inspection in July 2023, according to a letter sent to PG&E on August 24, 2023.
The FERC letter reads, in part:
Corrosion was observed on the turbine shutoff valve (TSV) and pressure regulator valves (PRV) at Powerhouse No. 1. PG&E should clean and recoat these valves or describe the maintenance program for doing so.
FERC letter to PG&E dated August 24, 2023
PG&E filed a response to FERC on October 9, 2023 – due to the response containing critical energy/electric infrastructure information (CEII), the details are not available. We requested an update from PG&E about their proposed fix and are waiting for a response to the query. At this time, it is unclear if the issue reported in July is responsible for the current infrastructure failure.
Editor’s note March 26, 2024 at 12:57 PM PG&E spokesperson Paul Moreno got back to us today and stated: “PG&E, FERC, and independent consultants inspected the valve bodies of the turbine shutoff valve (TSV) and pressure regulating valves (PRV) during a routine planned 5-year detailed inspection of the Lake Spaulding Project. Surficial coating issues and minor corrosion were identified on the exterior of the valve bodies by FERC. The external coating issue of the valve bodies is not related to the emergency work on the downstream discharge horns which are embedded in concrete and submerged during normal operation.”
PG&E infrastructure failure ripple effects to last longer
The return to service (RTS) date for Spaulding #1 powerhouse was extended to June 8 from the original April 30 date. PG&E spokesperson Paul Moreno, in response to an email from YubaNet, stated: “after the water tunnel was drained and we were able to better access the PRV [pressure relief valve] discharge pit during the week of March 15. We identified more damage that will take additional time to repair. Initially we believed the discharge horns (bends in pipe) cladding could be repaired but the cladding will need to replaced and grout and concrete around it also replaced.”
The water tunnel Moreno is referring to is a 963-ft-long, 104-inch-diameter rock tunnel that diverts up to 600 cfs of water from Lake Spaulding to the powerhouse.
Spaulding #1 Powerhouse is located downstream of Lake Spaulding and discharges, along with the Spaulding No. 1 Powerhouse bypass, up to 840 cfs into Drum Canal, which is a part of the Drum No. 1 and No. 2 Development. The powerhouse features semi-automatic operation and is scheduled as base-loaded for downstream water demand. Spaulding No. 1 Powerhouse has an installed capacity of 7.0 MW with a synchronous generator and one Francis turbine with a nameplate hydraulic capacity of 600 cfs. All hydropower production is halted during the outage.
The outage will be affecting the Deer Creek and Bear River systems, both dependent on diversions from Spaulding to maintain normal flows. In practical terms, Scotts Flat Lake and Rollins Reservoir won’t receive any additional water except the natural runoff from storms and maybe some snow melt from lower elevations.
Compounding the issue: South Yuba Canal rockslide
During a winter storm, a rockslide occurred on the PG&E-owned portion of the South Yuba Canal.
“PG&E’s usual alternatives to provide water to the South Yuba Canal and Bear River are dependent on the South Yuba Pipe which is currently out of service due to damage from a rockslide during a recent storm. PG&E has initiated an emergency project to return the pipe to service. The location of the damaged section of pipe, snow accumulation and inability to address the stability of the slide area is inhibiting safe access and working conditions. Long lead time material have been ordered and repair plans developed to expedite repairs once safe access is established,” Moreno replied to our question.
This issue is separate from the powerhouse failure.
NID to pass emergency resolution on Wednesday
On Friday, Nevada Irrigation District (NID) provided an update on the impacts this will have on the irrigation season, slated to begin April 15th. The news release included a “call for a voluntary water reduction of 20 percent by all District water customers for the remainder of 2024.”
Jennifer Hanson, NID General Manager, clarified the current situation in response to our question: “Looking to the irrigation season, which begins on April 15, we will have a limited water supply in our foothill storage reservoirs of Rollins and Scotts Flat. We ask that all District customers conserve so that there is water to meet the many demands of our community. NID will continue to post updates about this situation as more information becomes available.”
On Wednesday, March 27th during their regular board meeting, NID Directors will consider “a resolution declaring a water shortage emergency, authorizing extraordinary water conservation rules and regulations, and authorizing emergency activities and projects as related to Pacific Gas and Electric Company’s (PG&E’s) unplanned outages on the South Yuba Canal and Spaulding Reservoir.”
In the staff report for the resolution, staff lays out the issue:
It is anticipated that the demand for water will increase significantly with warming temperatures in the spring and summer months. The inability to move water from the District’s upper reservoirs will require reliance on Scotts Flat and Rollins Reservoir storage to deliver water during the outage period. PG&E has estimated that the repairs should be completed by June 8, 2024. If the Drum and South Yuba Canal is not repaired by the June 8 target date, the District will not be able to fully serve the water needs and demands of irrigation water users.
NID Board meeting agenda for March 27 – item 4.B
The NID Board meeting starts at 9:00 am in the NID boardroom on West Main Street in Grass Valley. You can also participate via Zoom and the meeting will be available later on the district’s YouTube channel.
All of NID customers affected
NID owns and operates over 400 miles of canals and 300 miles of treated water pipelines. This excludes the cities of Nevada City and Grass Valley which have separate contracts with NID.
The water supplied from the South Yuba Canal affects all NID Nevada and Yuba County customers. The water supplied via Drum affects all NID Placer County customers. Essentially, all NID customers are affected.
Grass Valley and Nevada City, while technically not within the NID district, will continue to receive treated water. “The rescinding of the surplus declaration would have detrimental effects to the water supply contract with the City of Grass Valley and Nevada City. Leaving the surplus declaration in place allows continued supply to the cities,” NID responded to our question about the existing surplus declaration – a necessary step to sell water ‘outside’ the district i.e. to Nevada City and Grass Valley.
NID is also in the process of informing boaters with slips on Rollins and Scotts Flat of the expected drawdown and very low reservoir conditions.
Impacts on local farmers and ranchers, recreation opportunities and the local economy will be detailed in a forthcoming story.
