Shawn Raley and Aaron Burrough, Global Air Operations Group, reveal why ground application should become a standard complement to aerial firefighting.
The iconic image of retardant falling from an airtanker has shaped wildfire suppression for decades. But as fires become more unpredictable and resources more constrained, applying the same technology from the ground could unlock a powerful new layer of protection.
Long-term fire retardant has been an aerial tool for more than 60 years, tested through the USDA Forest Service Wildland Fire Chemical Systems program and listed on the agency’s Qualified Products List. What has not changed is where we apply it. While fires burn hotter, move faster and grow larger, ground application should become a standard complement to aerial firefighting rather than an afterthought called in once the aircraft are grounded.
Long-term retardant does not suppress fire the way water does. Water absorbs heat and foam creates a temporary oxygen barrier; retardant changes the combustion pathway of the fuel itself. When the water carrier evaporates, the phosphate residue remains active in the fuel bed, promoting char formation rather than flaming combustion. It stays effective through wind, heat and smoke until rainfall or mechanical action removes it.
That persistence makes ground application strategically valuable. A retardant line strategically placed ahead of a fire greatly slows or stops spread without crews holding position. It can be placed accurately on critical infrastructure, around structures and subdivisions, and on other values at risk hours or days before a fire arrives.
Ground application does not replace aerial retardant. It works when aerial retardant cannot and before the fire forces the decision. Aerial windows often close because of low visibility, high wind, darkness, smoke or terrain, meanwhile the fire does not stop burning.
Aircraft availability on significant fire weather days is also finite. When multiple fires are running, air resources are triaged and airtankers are committed before the next ignition occurs. Ground application does not compete with that system, it complements it. A crew that pretreated a subdivision or a contingency line the night before has already accomplished what would otherwise require multiple airtanker loads, freeing aircraft for the active perimeter where their speed and reach cannot be matched from the ground. Ground retardant does not replace air. It multiplies what air can do by covering the ground it cannot.
The platforms are already available: standard water tenders, Type 3 and Type 6 engines, retardant application trailers, brush trucks, UTVs with tank kits and backpack sprayers. There is no specialized equipment requirement. The product simply needs to be prepositioned, and crews trained to use it.
The timing math is decisive. Research published in the Proceedings of the National Academy of Sciences by Stanford researchers found that proactive treatment of a high-risk area required roughly 20,000 gallons of retardant, compared to an estimated one million gallons once a fire was actively spreading. Getting the right product on the ground before the fire arrives is an order of magnitude better.
The clearest recent example of ground application done right is Sierra Madre Fire Department in California’s San Gabriel Valley. Rich Snyder spent 36 years there, building one of the country’s most sophisticated ground retardant programs, including a standing pretreatment program around Pasadena’s Rose Bowl before each Fourth of July.
When the Bobcat Fire threatened Sierra Madre, Arcadia, and Monrovia in 2020, Snyder coordinated the deployment of PHOS-CHEK from ground-based apparatus ahead of the fire, pretreating structure perimeters and fuel transitions while aerial assets were limited by smoke and darkness.
One protected target was the historic Trask Boy Scout Camp above Monrovia. The camp had gone unmaintained during COVID and was considered vulnerable. Sierra Madre Fire mixed roughly 1,800 gallons of retardant and applied it around the buildings.
Days later the fire reached the canyon but did not get past the retardant lines. No structures were lost. The success came not from better equipment but from a doctrine built over decades. When the aerial window closed Sierra Madre was still working.
Ground-based units can be prepositioned ahead of a moving fire to protect critical infrastructure, keep evacuation corridors open, treat planned firing operations and identify Safety Zones and Temporary Refuge Areas before conditions make that work impossible from the air. Keeping ingress and egress routes open is not a luxury; it allows crews to work and communities to leave.
The Dragon Bravo Fire at the Grand Canyon’s North Rim in July 2025 shows the cost of missing that opportunity. The fire ignited on July 4 from a lightning strike, giving managers nine days before it reached the developed area on July 12. In that Industrial Firefighting time, no ground-applied retardant was used. The fire destroyed the historic Grand Canyon Lodge, along with 106 surrounding structures, at a suppression cost of $124 million.
When the lodge was threatened, aerial retardant was blocked on two fronts. A chlorine gas leak at the water treatment facility made drops chemically dangerous, and interagency retardant avoidance areas prohibited drops in the lodge’s vicinity. The aerial window was closed. The ground window had been open for over a week. The cost of pretreating that structure complex would have been measured in the low thousands of dollars. The loss was measured in the hundreds of millions.
Contingency groups deserve particular attention. On Type 1 and Type 2 incidents, they work ahead of the main perimeter, building line, prepping infrastructure and establishing fallback positions. That is exactly where ground-applied retardant belongs. A contingency group treating structure clusters, road corridors and fuel transitions creates protection that remains active when the crew moves on, works through the night and holds when the fire tests the position the next afternoon.
The same logic applies to planned firing operations. Incident management teams often limit direct attack because of firefighter safety, terrain or fire intensity, then follow with a firing operation.
Retardant works. The aerial delivery system that has defined it for six decades works too and it remains irreplaceable. But today’s fire environment produces rates of spread, flame lengths and spotting distances that regularly outpace reactive suppression. Retardant chemistry reaches its full potential when ground crews treat the right fuels at the right time, in the hours and locations where aircraft cannot operate.
Departments that make ground application standard are protecting structures and infrastructure that would otherwise be lost. The rest of the profession is one paradigm shift away from the same outcome. The retardant has been there all along. The question is whether we are willing to apply it from the ground.
