An inside look at a prescribed burn on Thomas Mountain

Twigs and brush crackled in bright orange flames, ash rained from the sky and a plume of gray smoke rose into the air on Thomas Mountain earlier this week as dozens of firefighters worked methodically to contain a swath of flames.

The scene, seemingly chaotic at first glance, was actually part of a prescribed burn by U.S. Forest Service firefighters that had been planned out long in advance in an effort to reduce grasses and twigs that could help a fire spread. The operation was being done primarily to help protect the nearby Garner Valley and Anza Valley areas, according to firefighter Matt Ahearn.

Thomas Mountain is between Highway 371 and Highway 74 in the San Jacinto Mountains. Firefighters, Monday, April 2, were working on a 769-acre area known as the Thomas Mountain Unit 1, one of five different areas on the mountain that need to have prescribed burns.

Ahearn said the objective was to burn between 30 and 70 percent of one-hour and 10-hour fuels within the Unit 1 area. He explained that one-hour fuels are things such as light grasses that will be completely burnt within a one-hour time frame whereas 10 hour fuels are twigs and sticks up to a quarter of an inch in diameter.

U.S. Forest Service officials advised members of the public that a plume of smoke could be visible from the surrounding area for as long as a week as firefighters do the burn.

"We start active firing today, and from this point on the project will be staffed for 24 hours a day until we're done firing," Ahearn said of the work on Unit 1. "Once we're done firing we'll go into a holding pattern and it'll still be staffed 24 hours a day until we deem it comfortable that we can start downstaffing it."

He said Unit 1 would be staffed for more than a month to make sure that every hot spot was completely out.

Monday's operation began with a briefing where firefighters gathered together and went over such things as weather, safety tips and the boundaries of the controlled burn before dispersing for a test fire – basically a test-run where a small patch of brush is burned to make sure that a fire will behave as expected and that it won't grow out of control.

From there the firefighters got out their igniter-topped drip torches filled with a mixture of gasoline and diesel fuel and began lighting the dense grassy growth ablaze.

Firefighter Pedro Barba did the burn in small sections, lighting one area ablaze and letting it get to a smolder before moving to the next area.

Supervising the prescribed blaze was Forest Service Hotshot Squad Boss James Blair, who said it was his job to monitor firefighters to make sure they were burning brush at the right pace and intensity and also to make sure the fire stayed within an established containment line.

"If we do get something that gets out of the line or gets into something that we don't want it to, we'll take aggressive action to extinguish the fire, see where we're at from there and re-engage," Blair said.

Though the objective of the controlled burn was to burn grasses and twigs, occasionally the flames would consume one of the towering Ponderosa Pines. A loud wooshing noise could be heard. Intense heat radiated from the trees as they burned within a matter of minutes.

By midday, a large swath of brush had been burned through and firefighters had made their way down the dirt path they had also used as a line to keep the fire boxed in.

Ahearn said that the Forest Service must sometimes prepare a community and ease their concerns about a prescribed burn. He said that's especially the case in the San Jacinto Mountains. Firefighters haven't been able to do as many burns there because their attentions have been diverted to actual wildfires and people aren't accustomed to them.

"The biggest misconception is the word fire in California is immediately related to the last catastrophic wildfire," Ahearn said. "We're trying our hardest to get the community involved, get the message out to let them understand that there's different types of fire for different purposes."

Some of the efforts the Forest Service has used to inform the public include community meetings, flyers, message boards and radio announcements.

"Not all fire is necessarily bad fire," Ahearn said. "Planned under the right conditions prescribed fire can actually can actually do a lot of good to prevent those massive California wildfires that everyone is accustomed to."

Alex Groves can be reached at [email protected].