A helicopter with a suspended saw trims trees along EWEB’s Carmen Smith tap line to mitigate impacts that can lead to outages and wildfires.

Keeping trees and brush from tripping transmission lines out of service, possibly sparking wildfires and compromising public safety, is a year-round job for the Bonneville Power Administration.

With lines traversing 8,500 miles of right-of-way corridors, many in rugged and forested Northwest terrain, sometimes it’s safer to take an aerial approach to vegetation management. A helicopter equipped with a saw can quickly and safely trim tree tops and overreaching limbs.

On Oct. 20, BPA partnered with the Eugene Water & Electric Board to host a media observation, demonstrating how helicopters help power utilities effectively and safely trim vegetation that could disrupt power lines.

The trimming and observation took place an hour east of Eugene, Oregon, along EWEB’s Carmen-Smith transmission line, which runs through the Willamette National Forest. This line is a vital connection for EWEB’s electric distribution system and links to BPA’s transmission system. It allows generation from EWEB’s Carmen-Smith Hydropower Project to serve EWEB customers in Eugene and the McKenzie River Valley or to move onto BPA’s transmission network, allowing EWEB to market the power to electric utilities across the West.

The helicopter, hired by EWEB and operated by Medford-based Heli-Dunn, used a suspended saw device to top trees and trim off branches growing too close to the power lines. You can view a video below. Earlier in October, BPA used Heli-Dunn’s services to trim along one of its power lines near Detroit, Oregon.

BPA’s rigorous vegetation management program has been in operation for over 30 years.

 The program covers routine scheduled maintenance of the transmission lines, access roads and other facilities, as well as emergency or imminent threat vegetation removal. By using helicopters, BPA reduces environmental disturbance on the ground while also safely gaining access to remote, mountainous areas that are treacherous for tree-trimming crews to reach by foot.

“Helicopters are especially handy on steep terrain after wildfires have left the ground bare or unstable, and this instability can worsen during the winter months,” said Jennifer Strombom, one of 10 natural resource specialists responsible for identifying vegetation that could damage BPA towers and structures. “If we had ground crews falling trees and hiking in that kind of terrain, it would take significantly longer to do the same work and pose safety risks. It also would have required a line outage given the difficult-to-control behavior of the fire-damaged trees and ground terrain.”

EWEB estimated that without the use of the helicopter to trim along the Carmen-Smith line, the job would take three years and cost eight times more due to factors such as wildlife protection measures, fire season restrictions and inaccessibility of the rugged landscape. With the helicopter, the job was completed in one week.

As an added benefit to efficiency and safety, the helicopter crew can complete the aerial work while the line remains energized, though EWEB did decide to de-energize its line to complete the work.

The area surrounding the Carmen-Smith line is also vulnerable to fire during the warmer months, increasing the need for efficient vegetation management. Helicopters trim trees quickly and proactively reduce the risk of igniting fires caused by power lines, which can occur when tree branches touch energized lines.

“Electricity wants to get out of the line and move to the ground, so it looks for anything that it can use as a path to do that,” said BPA spokesperson Doug Johnson during the trimming observation. “The last thing we want is for a tree limb to blow into a power line or grow close enough to spark a fire.”

This was the first time in several years that EWEB used a helicopter for vegetation management. However, with climate change bringing hotter, drier summers and longer, more intense wildfire seasons, the utility is likely to use helicopters more frequently in the future.

Read more about the importance of BPA’s vegetation management program at Trees and power lines: A growing concern. Learn about the team behind BPA’s vegetation management program in this article. You can also read about vegetation management and the role it plays in BPA’s Wildfire Mitigation Plan.