Crews from the San Francisco Public Utilities Commission (SFPUC) are working to repair 230-kV transmission lines from the Hetch Hetchy power system that were damaged by an out-of-control wildfire burning in wooded land east of the San Francisco Bay area.
The Rim Fire, which started Aug. 17, damaged the Kirkwood powerhouse and the roof of the Holm powerhouse and knocked out of service a 12-mile stretch of 230-kV transmission that carries the power generated by the power system to the utility and its customers. Both the Kirkwood and Holm powerhouses were damaged and remain offline, though repairs have been completed to a damaged turbine at the Kirkwood plant. A third facility, the Moccasin powerhouse, escaped undamaged and continues to generate electricity.
Earlier reports that the transmission line had been completely destroyed proved to be inaccurate, an SFPUC spokesperson told TransmisssionHub Aug. 29. Crews from Pacific Gas & Electric (PG&E) plan to use a helicopter to fly SFPUC personnel over the transmission lines to assess the damage from the air. Once the necessary repairs are identified and completed, the lines must be hot washed to rid the insulators of dirt and other debris prior to returning the lines to service.
For its part, the Rim Fire forced PG&E to deenergize one 12-kV distribution line for the safety of firefighters and others in the area. It has also damaged some components of PG&E’s infrastructure, but the utility is still assessing the damage because it hasn’t been able to get to all of the areas where equipment has been damaged. Approximately 120 PG&E customers are without power as a result.
“We have crews out there and we have started repairing what we can,” a PG&E spokesperson told TransmissionHub. “We have reconstructed seven circuit miles of line, and we’re using helicopters to both assess the damage and do the repairs.”
Approximately 50 crew members are working to repair the damage to the powerhouses and equipment. In the meantime, the utility is replacing the power from those facilities by accessing power in an existing power bank and purchasing power on the open market. All of San Francisco’s municipal electric customers continue to be fully supplied with no service interruption, SFPUC said in a statement.
On a related note, SFPUC reported that some ash has fallen onto the surface of the Hetch Hetchy reservoir but has not resulted in any deterioration of the quality of the water, which is withdrawn at a depth of 260 feet below the surface.
“The Hetch Hetchy Regional Water System continues to deliver high-quality water to 2.6 million water customers in San Francisco and throughout the Bay Area,” the agency said in a statement issued midday Aug. 30. In addition to electricity, the organization provides retail drinking water and wastewater services to San Francisco, and wholesale water to three Bay Area counties.
The fire itself had blackened almost 202,000 acres of brush, oak, and pine by midday Aug. 30 and was slightly more than 30% contained. Officials estimate the fire will not be fully contained until Friday, Sept. 20.
Meanwhile, firefighters have fully contained a wildfire that blackened almost 11,500 acres in northern California and at one point caused concern among officials at the California ISO (Cal-ISO) for the Pacific AC Intertie (PACI), which runs parallel to the fire’s path. That fire started Aug. 23 about 12 miles east of Los Molinos, Calif. The cause of both fires is still under investigation.
The PACI is part of the larger Pacific Intertie that consists of three AC lines and one 800-kV DC line. The AC lines begin at the Bonneville Power Administration’s (BPA) John Day substation near The Dalles, Ore. Two of the AC lines terminate at Southern California Edison’s (SCE) Lugo substation near Los Angeles, and the third line ends at PG&E’s Tesla substation east of San Francisco. The DC line runs from BPA’s Celilo Converter Station near The Dalles Dam on the Columbia River through Oregon and Nevada, and terminates at the Los Angeles Department of Water and Power’s Sylmar Converter Station north of Los Angeles.
SCE is a subsidiary of Edison International (NYSE:EIX), while PG&E is a subsidiary of PG&E Corporation (NYSE:PCG).