By Katherine Blunt

Evidence is emerging that an inactive power line owned by Southern California Edison ignited the Eaton fire, which killed 17 people and destroyed part of the Los Angeles area last month.

The utility said it is investigating the possibility that active high-voltage transmission lines near the suspected ignition point could have sent electricity into a nearby inactive line, giving it enough power to spark the fire. The company had said it hasn't found indications that the fire resulted from any of the active lines, all of which remained energized when the fire started on Jan. 7.

SCE, a unit of Edison International, said Thursday that it discovered damage on the idle line, which runs parallel to the four active lines in the Eaton Canyon, where investigators said the fire started before spreading to destroy much of nearby Altadena. The company said it plans to examine parts of the idle line in a laboratory, and that it plans to strengthen its safety practices involving other lines that are no longer in service.

The inactive line, which has been out of service since 1971, was supposed to be outfitted with equipment to send errant electricity directly into the ground, reducing the risk of sparks. SCE said it discovered damage to the grounding equipment on part of the line, though it doesn't know when it occurred or what role, if any, it might have played in the fire.

"While SCE's investigation remains ongoing, SCE has taken immediate steps to further strengthen and standardize its grounding practices with respect to idle lines," the company said in a regulatory filing.

It might take months for fire investigators to determine the cause of the Eaton fire, which burned more than 14,000 acres and destroyed thousands of homes and businesses. If SCE's equipment is found to have ignited it, the utility will likely face billions of dollars in liability costs. Plaintiffs' attorneys have already filed several lawsuits against the company, alleging that its power lines played a role.

Mikal Watts, a Texas-based attorney suing SCE on behalf of some fire victims, said he is mounting a case to try to prove the idle transmission line ignited the fire. He said he plans to argue that the grounding equipment was faulty, resulting in sparks as the current traveled from the overhead wire to the flammable vegetation beneath the transmission tower.

"If it's not tied off appropriately, you have grounding problems," he said. "That electricity doesn't dissipate into the ground like it should, and that leads to arcing."

In the hours before the start of the Eaton fire, SCE shut down part of its network of low-voltage distribution lines in and around Altadena to reduce the risk of their sparking on contact with tree branches or other objects. Utility employees debated whether to cut power in the Eaton Canyon to the four transmission lines, which are higher-voltage and typically pose less risk than distribution lines, but ultimately decided that anticipated wind speeds didn't warrant doing so.

In the evening, as wind speeds picked up, surveillance footage from a nearby gas station showed what appear to be flashes on the active lines in the canyon, a possible indication of electricity's jumping from one line to another. Flames ignited moments later.

Altadena residents recorded video footage of the fire blazing beneath a transmission tower supporting the idle line.

Michael Wara, a lawyer who directs the Climate and Energy Policy Program at Stanford University and studies wildfire-mitigation strategies, said SCE's disclosure should prompt examination of how SCE maintained and inspected the idle line before the fire, and whether the company should have removed it entirely upon taking it out of service.

"How would they know what the condition of the grounding wire is?" he asked. "That, to me, raises so many questions."

SCE said its investigation of its equipment is complex because the potential cause -- the jumping of electricity from an active line to an inactive one -- is relatively uncommon in wildfire ignitions. Power lines have caused a number of major wildfires in the U.S. within the past decade, most often after coming into contact with trees or other objects during severe windstorms.

Idle transmission lines have been shown to pose fire risk. In 2019, part of a transmission line owned by PG&E broke and ignited the Kincade fire, which burned nearly 78,000 acres in Northern California.

The transmission line, which wasn't in use at the time of the ignition, had been partially decommissioned. California regulators determined that PG&E should have removed the line after taking it out of service and fined it $40 million for failing to do so, among other violations.

As part of a regulatory settlement, PG&E agreed to spend $85 million to remove 72 abandoned transmission lines in its service territory. The company said it would give priority to the removal of idle lines at the highest risk of becoming energized as a result of their proximity to active lines.

"Failing idle facilities can pose significant wildfire and safety risks, " the company said at the time of the agreement.

--Dean Seal contributed to this article.

Write to Katherine Blunt at katherine.blunt@wsj.com

(END) Dow Jones Newswires

February 06, 2025 19:36 ET (00:36 GMT)

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