Over the years, utilities around the nation have had to deal with wildfire-related damage to their transmission and distribution lines, especially those that traverse wilderness areas. Now, there is growing evidence that, in some instances, the power lines themselves are triggering the wildfires.

In some instances, high winds can blow nearby trees and their branches into power lines, sparking fires. In other cases, wind can snap wooden distribution line poles, causing live wires to fall onto nearby dry grass, setting it on fire.

While such problems exist in a number of states, the most serious problems have occurred in California, especially over the last two years. Record-breaking wildfires have erupted as a result of the unprecedented drought the state has experienced, which has turned millions of acres of forest into tinder boxes.

In late 2017, for example, power lines owned by Pacific Gas & Electric (PG&E) were blamed for a dozen Northern California wildfires and 18 related deaths. A report, issued by the California Department of Forestry and Fire Protection, noted that these fires started when trees and branches came into contact with power lines. One such fire, the Redwood Fire, burned over 36,000 acres, destroyed 543 structures, and resulted in nine civilian deaths. Another, the Atlas Fire, burned 52,000 acres, destroyed 783 structures, and resulted in six civilian deaths.

During the summer of 2018, the Department reported at least 17 more major wildfires that were triggered by power lines. One of these, the Thomas Fire in the southern part of the state, was triggered by Southern California Edison lines. That fire destroyed 1,000 buildings and led to a landslide that killed 22 people.

By far the worst fire in the state's history, the Camp Fire has killed at least 85 people and destroyed 14,000 homes. While the exact cause has yet to be determined, the fire did start near some PG&E transmission lines that experienced an outage just 15 minutes prior to the start of the fire.

According to a Cal Fire incident report, the Camp Fire is now officially contained.

While the California Public Utilities Commission (CPUC) estimates only about 10 percent of the state's wildfires are triggered by power lines, the frequency and severity of these wildfires has caused the CPUC to expand its probe into PG&E power line safety practices and even consider breaking the utility up into smaller utilities to facilitate more management accountability for power line safety.

In addition, there is a growing outcry from among many in the state for utilities to become more aggressive in burying power lines, especially transmission lines that traverse heavily forested areas. Such an effort is not cheap, of course. An article in the San Francisco Chronicle reported undergrounding of that type can cost up to $5 million a mile and that it would cost PG&E over $100 billion to underground all of its high-power lines. Besides the cost, there is concern about digging in environmentally sensitive areas.

Still, such work is being done in parts of the state. San Diego Gas & Electric reports that 60 percent of its lines are now underground, including rural lines running through areas that are prone to wildfires. And, the utility just announced plans to begin converting another 20 miles of overhead lines to underground in a rural area with a high fire risk in its service territory.

While undergrounding is often prohibitively expensive, there is also a growing interest in having utilities insulate their power lines, making them less likely to trigger sparks and resulting fires.

In the meantime, the main focus, of course, is more aggressive right-of-way work to keep trees and branches as far away from power lines as possible.