Authorities have for years envisioned a scenario in which power lines would cause the next devastating California wildfire. Now Cal Fire is investigating whether the deadly Butte Fire was caused by a Pacific Gas and Electric Co. electric service line.
"A live tree may have contacted a PG&E line in the vicinity of the ignition point," PG&E's Barry Anderson wrote in a statement.
The utility said it is fully cooperating with Cal Fire's investigation.
State law requires utilities to maintain clearances between power lines and trees, which requires trimming. Also, if a utility is notified of dead or rotten trees leaning toward power lines, the companies are responsible for removing them.
Mohler said Cal Fire investigators will examine PG&E service and inspection records for the area around the fire’s suspected origin.
PG&E spokesman Joe Molica said that the tree in question was given six separate inspections in 2014 and 2015 and was not identified as a risk.
The California Public Utilities Commission is also investigating the cause of the blaze.
"The conductors can actually sag quite a lot, just depending on the temperatures," California Public Utilities Commission Safety Enforcement Director Elizaveta Malashenko told KQED. "You look at a power line, and it seems like it’s pretty high and far away from the ground -- it’s more or less a straight line between the poles. You can come back to the same area on a different day when you have higher load, higher temperatures, and have that sagging quite a bit."
She said that wind and rainstorms can also cause trees and power lines to move in unpredictable ways.
"You know you can have a great vegetation management program, but it only takes a one-time issue to start a major fire," Malashenko said. "I think the utilities have been doing a lot."
The CPUC could fine PG&E if the utility failed to adhere to state laws.
Not including the Butte Fire, electrical power problems have caused five large fires throughout California since 2010, according to Cal Fire data.
Fire Prevention Ramped Up During Drought
Utilities have spent millions on preventive measures since the drought began, forging public-private partnerships to prevent just such a scenario.
And in response to Gov. Jerry Brown's declaration in early 2014 that the drought constituted an ongoing state of emergency, the California Public Utilities Commission’s acting Safety and Enforcement Division director issued a letter to all of California’s utilities directing them to “take all practicable measures necessary to reduce the likelihood of fires.”
That meant increasing inspections in fire-threatened areas, among other things.
PG&E announced last month that the company supports a Cal Fire campaign pushing property owners to remove dying or dead trees infected with bark beetles, which have wiped out 85 percent of the trees in some communities.
"These dead trees are just waiting to go up in flames," said Dennis Mathisen, Cal Fire chief of public education.
The utility is also removing more trees. It has removed about 107,000 hazardous trees this year, PG&E told KQED, more than double the 50,000 trees cut down in 2010. It plans to trim or remove about 1.1 million trees by the end of 2015.
PG&E operates 134,000 miles of power lines, employs 350 foresters, and contracts with more than 650 private tree crews to patrol its lines.
Previous Blazes Caused by Power Lines
Two years ago, PG&E and its contractors agreed to pay a $50.5 million settlement in litigation over the Power Fire and the Whiskey Fire. The blazes burned more than 18,000 acres of national forest in October 2004 and June 2008, respectively.
PG&E paid a $14.75 million settlement to the U.S. Forest Service in 2009 after being blamed for the 1999 Pendola Fire. It burned for 11 days and scorched 11,725 acres, mainly in the Tahoe and Plumas national forests. The fire's cause: A rotten pine, which the government said PG&E should have removed, fell on a power line.
The utility also reached a $22.7 million settlement with the CPUC in 1999 after regulators found PG&E hadn't spent money earmarked for tree trimming and removal toward those purposes. Shareholders paid the settlement amount for future projects, and PG&E paid a $6 million penalty to the state.