Assistant Chief Drew Smith, LA County Fire Dept., and Assistant Chief Brad Weisshaupt, Forestry, LA County Fire Dept., explained the process of Prescribed Burns.
Prescribed Pile Burn in Santa Monica Mountains
I, like most people, have legitimate concerns about Prescribed Burns. On Monday, April 13th, I was fortunate to be invited to attend an event that the LA County Fire Department (LACoFD) has not held for 25 years: a Prescribed Pile Burn in the Santa Monica Mountains.
LACoFD has many items in its toolbox to reduce fuels. Prescribed Pile Burns are just one of their tools, but have not been available for use in the Santa Monica Mountains for decades. LACoFD has been advocating for the use of this tool because, when used under the correct conditions, Pile Burns are the right tool for the right job.
Pile Burns fall under the general category of Prescribed Burns, sometimes called Rx Burns. They are only conducted under optimal weather conditions that comply with local regulations, and only in calm, wet, or damp conditions. They require constant supervision, a burn permit, and strict safety measures—like keeping piles under 4 feet in diameter and height, creating a 10-foot cleared radius, and having hoses and fire trucks ready. Failure to take precautions can lead to escaped wildfires.
Why do Pile Burns?
The Pile Burn Tool is used when there is a buildup of dangerous, dried, and dead fuels in an area that cannot be reached by trucks for evacuation. The thinning of these fuels helps create fuel breaks to reduce and slow down fires.
Pile Burning can be divided into 4 stages:
Evaluation
The fire fuel build-up is evaluated by the fire department—when was the last fire in the area, what is the potential flame height and speed of the fire, etc. Topanga has not seen fires in many years, and the fuels have built up. This was a concern for LACoFD. The fire department always tries to find a balance, and this buildup of fuel was determined to be out of balance. The Fire Department worked with MRCA to determine the type and extent of fuel break they were seeking to create.
Thinning
The thinning is done by firefighters, ensuring only what needs to be removed is removed. The dead vegetation is then taken to the ridge line, where small piles are made. The firefighters only cut above the surface, leaving everything below, so the root mass is still there. Not only do they monitor the burn, but they also conduct immediate post-burn surveys, and 6-month and 12-month follow-ups to assess regeneration.
The thinning takes the dead out and surgically removes tons of fuel per acre. They don’t eradicate anything; they modify and maintain the potential fuel for wildfires.
Cultural monitors were on site during the thinning project. Indigenous communities have done cultural burning for generations to manage landscapes, promote biodiversity, and reduce wildfire risk. These practices are rooted in traditional ecological knowledge to restore ecosystems and support cultural resources. Beyond fuel reduction, these burns revitalize native plants, enhance wildlife habitats, and manage specific resources. Pile Burns are conducted in the spring and fall when conditions are cooler and more humid.
Burning
Test burns are done to monitor winds and smoke dispersal. The science behind all of this, from the vegetation management to the Pile Burn settings, is governed by methods of treatment and best practices. There were approximately 180-200 piles on both sides of Topanga Canyon to be burned. The dead vegetation, which had been brought up to the ridge line, was burned when all the “Mother Nature Conditions” were in balance—meaning, the fuels were in a certain state of moisture and dryness to get the intensity they wanted. The engine companies managed and monitored the intensity of each burn.
Monitoring
During the burn, they monitored hourly weather conditions using smoke trajectories and assessed the receptiveness of surrounding fuels in case an ember escaped. Weather temperatures should be below 80 degrees with a relative humidity level above 30 percent, and a relative humidity of 60-80 percent at night, to help cool down the burn areas. The conditions were perfect for this Pile Burn. Wind and smoke dispersal were also continuously monitored. The science behind all of this, from the vegetation management to the Pile Burns setting, is governed by methods of treatment and best practices.
LACoFD considered all these factors in evaluating the “Escape Fire Potential,” which they take very seriously.
How long did they stay after the burn to monitor it?
Resources monitored the burn all day, on the line and mobile, and then they put it into “patrol status.” Drones, with high-resolution infrared thermal detection technology, were used throughout the day and into the night. Crews remained on-site until there were no heat signatures.
Conclusions
I was very impressed with the professionalism and the process in which LACoFD conducted these Pile Burns. From the evaluation to the thinning to the burns, and finally to the level of monitoring, everything left me with a sense of trust that erased any fears or concerns.
CLICK HERE to view more information on Wildland Fuels Management Methods of Prescribed Burns.
Provided by LA County Fire Department.
Pile burn project map
Close to 200 firefighters managed the burns
Drone Pilots constant monitoring of the burn
Heat cameras on the drones can detect hot areas
LA County Fire Department crews
CAL FIRE crews
Lidar heat map cameras surveying the burn
Test burns are done before the burns
Dead vegetation, accessible only by foot, is taken to the ridge line and burned
10-foot cleared radius is established around each pile
180-200 piles burned on both sides of Topanga Canyon
Escape fire potential is taken very seriously with constant monitoring
