PG&E helicopter trims trees along power lines in rural Sonoma County forest

Flying about 220 feet above ground in Sonoma County’s northwest corner, a PG&E-chartered helicopter gave a loud buzz cut to towering trees that threaten to drop branches on 46 miles of rural power transmission lines.

Moving slowly above the redwoods and Douglas firs of the coastal mountains, the helicopter guided a 30-foot vertical saw — with eight whirling steel blades — over rugged terrain where tree limbs pose a threat to high-voltage power lines from Fort Ross to Fort Bragg.

Trimming 3 miles a day, the Heli-Saw is making its Sonoma County debut as PG&E’s ultimate vegetation management tool.

“We can do in one day what would take a crew of climbers three to four weeks,” said Brian Mulhollen, division manager/safety officer with Heli-Dunn, the Medford, Oregon-based company that works for PG&E throughout its 70,000-square-mile territory.

Approaching a clearing along Tin Barn Road in the Annapolis area Tuesday, the Astar 350 helicopter blasted observers with roaring engine noise and rotor wash as the clattering saw severed protruding tree limbs.

In the cockpit, pilot Casey Blacker peered through a large bubble in his side window to watch the tops of the trees ahead and keep the saw suspended on a pole below in his peripheral vision.

The biggest challenge, Blacker said during a refueling stop in a nearby field, is trimming trees through a canyon when the helicopter descends as the power lines ahead begin rising.

“It’s no fun,” said Blacker, who has thousands of hours of Heli-Saw flight time. “Things like that make more of a mental barrier. You get tense.”

At times the saw stops when it encounters a tree growing within another tree, sending a shudder up the pole and into the helicopter.

The job, in other words, is not for the faint of heart. “I’d never get in that thing if I wasn’t flying it,” Blacker said.

It is the newest piece of modern machinery mobilized for an urgent and closely watched job: Improving brush and tree clearance along nearly 100,000 miles of PG&E power lines in its vast Northern and Central California service area, where an estimated 120 million trees have the potential to grow or fall into lines, according to the utility.

Some of those lines and connected equipment have been blamed for starting Northern California’s deadliest and most destructive wildfires in recent years, and state officials have repeatedly urged the PG&E to bolster its efforts at vegetation management.

Deployment of the saw-equipped helicopter is poised to help treat hard-to-reach areas at a quicker clip than hand crews.

“The Heli-Saw is a fast, efficient way to obtain necessary clearances and reduce storm-caused outages, especially in areas of dense coniferous forests,” said Mark Stewart, a PG&E vegetation management supervisor.

The state’s largest utility, serving nearly 16 million people, says it trims or removes about 1.4 million trees a year to protect its equipment and customers.

The utility selected 46 miles of high-voltage transmission lines along the Sonoma and Mendocino coasts for the aerial pruning program.

The designated power lines have sustained a “high number of tree-related outages,” said Deanna Contreras, a PG&E representative. The trimming is intended to enhance the “safety and reliability” of the lines, she said.

Tuesday’s work was at the southernmost section of the project on a transmission line from Fort Ross to Sea Ranch. It marked the Heli-Saw’s first deployment in Sonoma County, but the helicopter has been used frequently in Mendocino and Humboldt counties, Contreras said.

Heli-Dunn operates a fleet of four sleek Astar 350 copters, nearly 36 feet long and painted silver and black with blue highlights.

“We call it a Lamborghini with a pickup bed,” Mulhollen said, because it is a high-performance machine like the famed Italian luxury sports car with “utilitarian features” that make it “a great aircraft for working in the woods.”

The Heli-Saw can operate in rain and snow and winds up to 15 mph, with fog the only limitation because it reduces visibility, he said. It can fly much faster, but typically moves at 15 mph or less and from 200 to 500 feet above ground.

The eight saw blades, suspending vertically from the helicopter at the end of a 100-foot pole, can rotate 360 degrees, controlled by the pilot and driven by a two-cycle gasoline engine that powers a hydraulic system that also spins the blades.

Heli-Dunn, which does tree trimming for utilities from coast to coast and also transports firefighters during wildfires, spent six months planning the Sonoma-Mendocino project, including aerial reconnaissance and selection of landing zones.

PG&E has been using the company to trim trees near transmission and distribution lines since 2017, including in remote areas across the North Coast and northern Sacramento Valley.

Blacker, the pilot on Tuesday, flies for five hours a day, making four to five passes over the same stretch of tall trees to trim all the branches above the power lines.

The Heli-Saw works in gaps of at least 15 feet between the power lines and the trees, and Mulhollen said in a decade of operation the company hasn’t once hit a line. Most of the time, the lines are shut off during tree-trimming operations, as they were Tuesday.

You can reach Staff Writer Guy Kovner at 707-521-5457 or On Twitter @guykovner.

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