Digging out, taking stock
PG&E looks for failure on Tuolumne Main Canal; TUD has a week’s backup supply
While Pacific Gas and Electric Co. crews were trying to locate a disruption on the Tuolumne Main Canal on Tuesday, the Tuolumne Utilities District general manager said TUD has about one week’s worth of stored water to get through the canal outage that was announced Tuesday morning.
“We don’t have any information on the problem on the canal, which is under PG&E control,” Don Perkins, TUD’S general manager, said Tuesday afternoon. “We’ve had to deal with this a number of times in the past. Generally speaking, we have about seven days of stored water.”
Outages on the 15-mile-long Main Canal are easier to deal with in the spring and summer than winter, though water demand at this time of year is less than during drier, warmer months, Perkins said.
When it’s working, the Tuolumne Main Canal conveys 95% of the water used by more than 40,000 TUD customers in Tuolumne County. TUD learned from PG&E on Tuesday morning that “the Tuolumne Main Canal has had a failure due to the storm,” a TUD spokeswoman said in an announcement.
“What we know right now is there is no water in our ditch system,” Lisa Westbrook with TUD said Tuesday. “PG&E is out there right now on snowcats to determine what happened. They are trying to locate it. We just know there’s no water right now. We’re asking everyone to conserve while we assess what repairs are needed.”
Perkins has been working for water agencies in Tuolumne County since 1991, first with Tuolumne County Water District No. 1, which became Twain Harte Community Services District, and then with TUD, where he’s worked since January 2000.
“Many, many times the canal’s been disrupted,” Perkins said. “A half-dozen times at least. Maybe a dozen times.”
Perkins recalled a Main Canal outage on Christmas Eve 1996, due to a tree that came down in a storm and broke an elevated flume between Lyons Dam and Twain Harte. PG&E estimated it would take a week to fix the busted flume, and completed
the work by Dec. 30 that year. Other outages on the Main Canal have occurred due to rockfall, snow, and slush blocking the ditches and flumes.
PG&E, which owns the Tuolumne Main Canal, had yet to explain what happened to the Gold Rush-era aqueduct system this time. They had yet to find the location as of Tuesday afternoon.
“At this time we don't know what is causing the disruption,” Jeff Smith, a PG&E spokesman, said Tuesday in a sequence of emails. Smith emphasized before noon Tuesday, “At this point, we do not know the cause, which means that it is not necessarily a failure, a break or damage.”
The Tuolumne Main Canal is a series of flumes and ditches between Lyons Dam and the powerhouse and penstock above Phoenix Reservoir. It's part of the Phoenix Hydroelectric Project, which includes Strawberry Dam, Pinecrest Reservoir, Lyons Dam and Reservoir, and
Phoenix Powerhouse. TUD has been negotiating with PG&E to acquire the Phoenix Hydroelectric Project, along with pre-1914 water rights and post-1914 water rights in the South Fork Stanislaus River watershed, since March 2020.
On Tuesday, getting access to the ditches and flumes that comprise the Tuolumne Main Canal was the biggest challenge facing PG&E workers.
About 95% of the water the District distributes originates from the South Fork Stanislaus River and is impounded in PG&E'S Pinecrest and Lyons reservoirs. PG&E owns and operates the canal and flume system to convey water from Lyons Reservoir to the Phoenix Powerhouse. TUD owns and operates a total of 71 miles of ditch, flume, pipe, and tunnel infrastructure that diverts water from the PG&E system at multiple locations.
Contact Guy Mccarthy at gmccarthy@uniondemocrat.net or (209) 770-0405. Follow him on Twitter at @Guymccarthy.