PG&E acknowledged late Tuesday that a worn hook on a transmission tower apparently failed before the massive Camp Fire -- as first reported by NBC Bay Area last week -- and ordered inspections of 5,500 miles of its electrical transmission network in fire-prone areas.
The company also suggested a second, lesser fire may have been the result of someone shooting into the line near the town of Concow. But the utility also said it found downed trees atop power lines in the same area.
In a 20-day supplemental report about both fires sent to state regulators with the Public Utilities Commission, the company identified the problem with a so-called C-hook that had secured a part of the 115,000-volt Caribou Palermo line to one of its transmission towers.
While noting its findings were "preliminary," the company identified what it called a flash mark on the tower where the line freed by the broken hook may have contacted the structure.
Subsequent inspection found unspecified signs of "wear" where the hook was connected to a series of discs that served as an insulator between the line and the tower structure. The company did not elaborate.
At the next-door tower, meanwhile, the company found an anchor for its insulator to the line had come loose.
As for the second, Concow fire nearby, the company said crews checking near where it started discovered a pole and other equipment "on the ground with bullets and bullet holes at the break point of the pole and on the equipment."
That discovery was on Nov. 9, a day after the fire started. Three days later, another patrol of PG&E found downed wires and poles, as well as several snapped trees, including some on top of downed wires. The company did not say whether the apparent gunfire or the downed wires touched off the fire.
"These incidents remain under investigation, and this information is preliminary,” the company stressed. "The causes may not be fully understood until additional information is available, including information that can only be obtained through examination and testing of the equipment retained by Cal Fire. PG&E is cooperating with Cal Fire."
On Monday, the company announced it was expanding inspections to 5,500 miles of its transmission system in fire prone areas, climbing or aerially inspecting some 50,000 poles and towers. The company announced it was bolstering weather monitoring and installing 600 new high-definition cameras to cover about 90 percent of fire threatened service territory.
In a statement, the company said: “The loss of life, homes and businesses in the Camp Fire is truly devastating. Our focus continues to be on assessing our infrastructure to further enhance safety, restoring electric and gas service where possible, and helping customers begin to recover and rebuild. Throughout our service area, we are committed to doing everything we can to further reduce the risk of wildfire.”