SAN RAMON, Calif. — Pacific Gas & Electric plans to bury 10,000 miles of its power lines in an effort to prevent its fraying grid from sparking wildfires when electrical equipment collides with millions of trees and other vegetation.

The daunting project announced Wednesday aims to bury roughly 10% of PG&E’s power lines at a projected cost of $15 billion to $30 billion.

Most of that expense will likely be shouldered by PG&E customers, whose electricity rates are already among the highest in the U.S.

PG&E stepped up its safety commitment just days after informing regulators a 70-foot pine tree that toppled on one of its power lines ignited a major fire in Butte County, the same rural area about 145 miles northeast of San Francisco where another fire sparked by its equipment in 2018 killed more than 80 people and destroyed thousands of homes.

Previous PG&E regimes have staunchly resisted plans to bury long stretches of power lines because of the massive expense involved.

But recently hired CEO, Patricia “Patti” Poppe, told reporters on Wednesday that she quickly realized after she joined PG&E in January that moving lines underground is the best way to protect both the utility and the 16 million people who rely on it for power.

“It’s too expensive not to do it. Lives are on the line,” Poppe told reporters.

However, getting the job done within the next decade will require a quantum leap. In the few areas where PG&E has already been burying power lines, it has been completing about 70 miles annually.