Power shutoffs kept downed trees and limbs from creating fire risk 190 times, PG&E says

If PG&E hadn’t shut off power in Northern California in late October, downed trees and limbs likely would have caused sparking on power lines 190 times, according to a Friday court filing from the utility.

The filing provides a new data point as the utility defends its decisions to enact the wide-ranging, disruptive shutoffs on windy and dry days last month against harsh criticism from Gov. Gavin Newsom and lawmakers.

In response to questions from a federal judge, PG&E reviewed damage to its lines after the shutoffs of Oct. 23, 26 and 29. The shutoffs each affected from 178,000 to 970,000 customers and thousands of miles of power lines from the Sierra foothills to the North Bay.

The filing identified instances of “arcing,” or sustained sparking that occurs when electricity moves through the air to another conducting surface. Cal Fire has said most of the destructive wine country fires of 2017 were caused by trees and vegetation falling on PG&E power lines.

During the Oct. 23 shutoff, which affected about 178,000 customers, vegetation damaged power lines 19 times, according to PG&E’s review. Of those incidents, 15 likely would have caused arcing if the lines had been electrified, according to the filing.

The utility grouped together the Oct. 26 and Oct. 29 shutoffs, since it reviewed the damage after the second shutoff. The shutoffs affected about 365,000 and about 970,000 customers, respectively.

During those shutoffs, trees and limbs damaged lines 241 times. The filing says lines likely would have arced in 175 of the instances if the power had been on. In the rest of the instances, conductors weren’t exposed or other circumstances prevented arcing, according to the filing.

In addition to the lines, PG&E reported on damage to its infrastructure. The utility found that four instances of damage to infrastructure during the Oct. 23 outage likely would have caused arcing, and that similar damage during the Oct. 26 and 29 outages likely would have caused arcing.

“PG&E welcomes the opportunity to continue our ongoing dialogue with the court about the extensive work we’re doing to further strengthen our infrastructure and reduce wildfire risk,” PG&E spokeswoman Karly Hernandez said in an emailed statement. “We share the court’s focus on safety and recognize that we must take a leading role in reducing the risk of wildfire throughout Northern and Central California. This reduction of risk is the sole focus of PG&E’s Public Safety Power Shutoff program.”

The utility provided the estimates in response to questions from federal judge William Alsup, who has been overseeing the company’s criminal probation from the 2010 San Bruno gas main explosion.

Some of the criticism directed at PG&E and its regulator, the California Public Utilities Commission, has been over the utility’s failure to adequately trim the vegetation around its lines that can cause the type of damage identified in the filing.