State regulators released reports from PG&E this week that document at least 20 cases of toppled trees and downed power lines across Northern California the night of Oct. 8 as strong winds buffeted the region and drought-parched vegetation ignited in quick succession from Sonoma to Butte counties, resulting in a series of deadly and destructive wildfires.
The reports show damage to the power lines and other PG&E equipment in areas close to the origins of the fires that burned 142 square miles of Sonoma County, killing at least 23 people and destroying about 7,000 structures, mostly homes.
Cal Fire investigators are looking into what caused the blazes. They have collected as evidence damaged power poles, wires and other pieces of utility equipment from at least 8 of 10 sites where PG&E reported “electrical safety incidents” in Sonoma and Napa counties, according to the new documents made public Tuesday by the California Public Utilities Commission.
“These are incident reports relating to the time the fires started,” commission spokesman Christopher Chow said. “There may be more reports coming in, so they’re not definitive.”
Spare and partially redacted, the 20 reports disclose sites where PG&E personnel have examined equipment failures, mostly caused by partial or whole trees falling into wires late Oct. 8 and early Oct. 9, when wind-whipped fires raced across the region.
PG&E is required to report all documented instances of tree branches and other vegetation and debris impacting electric lines to the utilities commission, which has launched its own investigation into the fires.
Pacific Gas and Electric Co. spokesman Donald Cutler said the incident reports published by the commission are preliminary and there may be more coming.
“There may be more incidences that need to be reported that we don’t have access to right now,” Cutler said.
Cal Fire investigators have closely guarded some of the areas to preserve evidence of how the fires may have been ignited.
Just north of Calistoga, private security guards were working 12-hour shifts last month at an area near Bennett Lane where the Tubbs fire started. The fire began shortly before 10 p.m. Oct. 8 and burned 36,807 acres on a westward path into northern Santa Rosa, killing at least 21 people and destroying 4,658 homes inside and outside the city.
Cal Fire investigators have seized power equipment as evidence from a house damaged by fire at an undisclosed location outside Calistoga, PG&E revealed in one of its reports. The main wires between power poles had detached from the burned home, the report said. Cal Fire took into evidence both PG&E and customer-owned power lines and other equipment from the site. The address is blacked out in the report published on the CPUC website.
In Mendocino County, PG&E reported, investigators found a broken tree near a downed wire in Potter Valley, an area where a firestorm there ignited, eventually burning 36,523 acres, destroying 545 structures and claiming at least nine lives. A nearby automated weather station recorded wind gusts of 40 to 50 mph that night, according to the documents.
In Kenwood, a 60-foot eucalyptus tree took down three overhead power lines, the utility said. The Nuns fire that broke out in the area would eventually burn 56,556 acres, destroy 639 homes and claim two lives in Sonoma County and one in Napa County.