California fire investigators say that the Camp Fire was caused by electrical transmission lines owned and operated by Pacific Gas and Electricity (PG&E) and located in the Pulga, California, area.

Cal Fire, which investigated the wildfire, said the blaze began in the early morning hours of Nov. 8, 2018, near the town of Pulga in Butte County. Dry vegetation and "red flag" fire warning conditions consisting of strong winds, low humidity and warm temperatures fed the fire and caused extreme rates of spread. The fire rapidly burned into Pulga to the east and west into Concow, Paradise, Magalia and to the outskirts of Chico.

The investigation also identified a second ignition site. The cause of that fire was determined to be vegetation that came into contact with electrical distribution lines owned and operated by PG&E. This second fire was consumed by the original fire.

The Camp Fire investigative report was forwarded by Cal Fire to the Butte County District Attorney Mike Ramsey.

In a statement, the utility said that it had not yet been able to review Cal Fire's report. However, it said that the agency's determination that PG&E transmission lines near the Pulga area ignited the Camp Fire "is consistent with the company's previous statements." The utility said it had not been able to conclude whether or not the second fire ignited as a result of vegetation contact with PG&E electrical distribution lines. It said that it "is fully cooperating with all ongoing investigations concerning the Camp Fire."

In late February, PG&E said that its equipment likely was the ignition point. It said it based its statement on information previously reported to state utility regulators. (Read "Equipment was 'probable' cause of deadly California fire, utility says.")

Timeline of events

According to the utility's timeline, at approximately 6:15 a.m. on November 8, the Caribou-Palermo 115 kV Transmission Line relayed and deenergized. At around 6:30 a.m. that day, a PG&E employee observed fire in the vicinity of what was identified as Tower:27/222. The employee called 911 to report the fire.

Later that day, PG&E observed damage on the line at Tower:27/222. Specifically, an aerial patrol identified that a suspension insulator supporting a transposition jumper had separated from an arm on the tower.

On November 14, according to the company, workers observed a broken C-hook attached to the separated suspension insulator that had connected the suspension insulator to a tower arm, along with wear at the connection point. In addition, a flash mark was observed on Tower:27/222 near where the transposition jumper was suspended. Damage to the transposition jumper and suspension insulator was identified, the utility said.

In addition, at around 6:45 a.m. on November 8, PG&E’s Big Bend 1101 12 kV Circuit experienced an outage. Company employees who patrolled the location saw damage to the pole and equipment and downed wires. Although Cal Fire has identified this location as a potential ignition point, based on the condition of the site PG&E said it has not been able to determine whether the Big Bend 1101 12 kV Circuit may be a probable ignition point.

The Camp Fire burned a total of 153,336 acres, destroying 18,804 structures and resulting in 85 civilian fatalities and several firefighter injuries. The Camp Fire is the deadliest and most destructive fire in California history. Cal Fire said that during 2018 there were more than 7,571 wildfires that burned over 1.8 million acres within the state of California.

To contact the author of this article, email david.wagman@ieeeglobalspec.com