From the stark, deeply incised rock face of Pusch Ridge to the spruce-lined top of Mount Lemmon, one color seems to have dominated the two-week battle of the Bighorn Fire: Flaming, searing red — maybe a cross between the hues of raspberries and some coral reefs.
It’s the color of the aerial fire retardant that firefighters dropped on many a ridgeline in an effort to slow the stubborn blaze, which has burned about 42,000 acres both inside and outside the Pusch Ridge Wilderness.
As of Thursday, 358,000 gallons of retardant — enough to fill more than 30 backyard swimming pools — had been dropped all around the Catalina Mountains. That’s almost 50% more gallons of retardant than were dropped onto all national forest wildfires in Arizona in 2016.
So far, with the fire now 22% contained, it hasn’t destroyed any homes, although at various times residents had to be evacuated from areas west, south and near the top of the Catalinas.
While fire officials say they think the retardant helped them fight the Bighorn blaze, a debate is roiling throughout the West over the chemical mixture’s effectiveness.
And while authorities say the candy-colored streaks and coatings left behind by the retardant should disappear within weeks, there could be other lingering effects.
There is environmental concern over the impact of the retardant on water and fish, although firefighters here say they do all they can to keep it out of the mountain range’s waterways. Invasive species possibly coming into the forest due to retardant dropping is also a concern.
Darrell Klesch, a longtime Oracle resident, said he’s happy the retardant was used after seeing it repeatedly stop the Bighorn Fire when dropped in the neighboring Catalina area where he regularly watched the fire in the past week.
“I can see the fire stop right at the line where it’s been laid down. It doesn’t jump there,” said Klesch. “The retardant is working reasonably well.”
Costs, benefits
Officials couldn’t say how much it cost to drop all that material in the Catalinas.
Aircraft use has soaked up the single biggest share of the Bighorn blaze’s estimated $10 million tab. Fire retardant accounts for only part of those costs. The DC-10s and helicopters that dump retardant are also used to drop water, for reconnaissance and in mapping efforts. Those aircraft also carry fire crews into remote areas and ignite firefighting burnout operations.
One cost estimate, prepared by the blog Wildfire Today, said the Forest Service pays $3 to $10 per gallon for retardant used by air tankers that are available only when needed, as opposed to tankers that the service has available 24/7.
A spokeswoman for the Incident Management Team leading the Bighorn Fire response pronounced the aerial retardant efforts “very successful,” saying they clearly helped slow the fire’s spread.
But spokeswoman Molly Hunter stopped short of saying the retardant was a principal reason that no homes have burned.
“No, retardant isn’t a stand-alone tool. This tool in combination with all the tools firefighters used (burnouts, sprinklers, fuel reduction, fire line, etc.) was what allowed firefighters to prevent fire from impacting structures,” Hunter said last week.
“Different tools or combinations of tools have been key factors at different times. The Incident Management Team develops plans on a daily basis that match the right tool or combination of tools to the circumstances at hand,” Hunter said.
It was good for Hunter to acknowledge the retardant didn’t stop the fire on its own, said Timothy Ingalsbee, executive director of Firefighters United for Safety, Ethics, and Ecology, of Eugene, Oregon. “It’s one of many tools, but an expensive tool, with extensive environmental impacts.
“That was an amazing amount of retardant, a phenomenal amount,” Ingalsbee said of the 358,000 gallons. “This sure smells like a retardant bombing boondoggle.”
How retardant works
As the Forest Service describes it, retardant is applied on threatened vegetation in the form of a chemical firebreak in front of an approaching fire. This solution coats the fuel.
Then, as the fire gets closer and the water contained in the retardant solution evaporates, the fire retardant component is supposed to react with cellulose present in the woody material, grass, needles and other matter which normally provide fuel for the fire, the Forest Service says.
As the fire heats up, the fire retardant material decomposes, giving off water vapor that cools the fire. It leaves behind a black, graphite-like, nonflammable carbon coating that insulates and restricts air flow to any residual fuels, the service says.
Hunter, the spokeswoman for Bighorn management, says fire retardant doesn’t stop or put out a fire. It’s put ahead of the strongest part of the blaze.
This video was taken on June 17 with the camera pointed to the northwest near the Mount Lemmon Fire District. Video courtesy of Southern Arizo…
“Sometimes it simply reduces the fire intensity and flame lengths enough so that firefighters can safely engage the fire. It doesn’t always stop the spread,” Hunter said.
Debate grows
The presence of large, DC-10-sized air tankers and much smaller helicopters has been a reassuring sight for residents near burning areas, making them feel the government is really on the job. Prodigious amounts of the retardant have been dropped all over the West, as many as 19 million gallons onto wildfires in 2016, records show.
But environmentalist critics say the federal government has spent far too much money on retardants without enough proven benefits. They say there’s never been a scientifically valid study proving retardants work as promoted.
“There is no dispute that fire retardant slows the advance of fire through some kinds of vegetation under some weather conditions,” said Andy Stahl, director of the Forest Service Employees for Environmental Ethics, in Eugene.
But slowing fire’s advance doesn’t mean retardant actually helps meet fire suppression objectives, such as decreasing the average fire size, Stahl said.
“No studies show it does. Nor do the available data show any correlation between retardant use and these outcomes,” he said.
Since 2012, the Forest Service has been working on a detailed study aimed at determining how effective its use of various aircraft has been in fighting wildfires.
A preliminary draft last year said the retardant was generally successful, depending on the type of aircraft used and how retardant and other materials are dropped. But it left a question: What did it mean by success?
The Forest Service declined to respond to a question about what its ongoing aircraft study defines as success.
The final study should be released soon, said Forest Service spokeswoman Jessica Brewen.
Does it change fire’s behavior?
But environmentalist Stahl said the Forest Service refuses to conduct the right kind of study to determine whether retardant really works: a “control” study to compare how a fire behaves with and without retardant, he said.
He said the Forest Service’s preliminary study on aerial firefighting’s success rate merely looked at whether retardant drops hit their targets, not at whether they changed fire behavior.
Hunter said she suspects there aren’t any fire retardant studies using control groups “because this would be extremely difficult if not impossible to do in a wildfire setting.”
A regional debate is also occurring over the retardant’s environmental impacts. The most common active ingredient in the retardant sprayed across Mount Lemmon and on most other wildfires is ammonium phosphate, a compound used in fertilizers.
In studies and in wildfires elsewhere, ammonium phosphate has been shown to be toxic to fish swimming in rivers, including salmon on the Pacific Coast.
The Forest Service’s rules on its use prohibit firefighting crews from dropping it closer than 300 feet from a water body, and Hunter said fire crews are confident that they’ve met that requirement in the Bighorn blaze.
Debates over the impacts accelerated after retardant dropped on an Oregon river killed 22,000 trout and other fish in 2002.
Years later, a lawsuit from Stahl’s group forced the Forest Service to prepare a 562-page environmental impact statement on aerial retardant.
Acknowledging retardant can affect fish — and that the Fish and Wildlife Service found the retardant could jeopardize the existence of 65 protected species — a 2011 statement concluded that the retardant was essential for firefighting.
Besides agreeing to leave the 300-foot buffer along rivers, the Forest Service also agreed to try to drop water or less-toxic retardant in areas occupied by protected species.
Today, Ingalsbee, Stahl and Susan Shaw, an environmental health scientist, are dubious about firefighters’ ability to keep retardant within the buffer.
A detergent-like chemical in retardant that quenches oxygen “is very effective” when dropped, said biologist Shaw.
“It gets into the gills. It prevents the fish from taking in oxygen from the water. It causes suffocation in fish and other aquatic animals,” said Shaw, founder and president of the nonprofit research group Shaw Institute in Maine.
“Fish will die”
Today, as climate change increases the size and scope of many wildfires, firefighters have to do more and more “heavy drops” of retardant in urban areas such as those surrounding the Catalinas in Tucson, she said. The smoke generated by big fires makes it hard to pinpoint releases to avoid streams.
“You can’t keep it out of waterways when you are dropping that much. You have tens of thousands of fish that will die,” said Shaw.
Hunter, however, said Bighorn firefighters avoid retardant drops in heavy smoke conditions precisely for those reasons.
Also, modern-day GPS systems have come a long way in controlling where retardant drops occur, said Dan Neary, a research scientist at the Forest Service’s Rocky Mountain Research Station in Flagstaff.
“But it gets more problematic with the steep terrain,” he said. “Drift (of the retardant) is also a problem in windy conditions.”
Hunter said a Forest Service biologist works closely with firefighters to insure they avoid waterways with their retardant drops.
When firefighters drop retardant within the Pusch Ridge Wilderness Area, they use a material containing a type of dye designed to fade really quickly, she added. When possible, they also try to drop water in wilderness instead of retardant.
“In all those decisions, they’re trying to weigh the impact on resources versus protecting lives and property,” she said.
Researchers continue to examine retardant’s impacts on water supplies. The U.S. Geological Survey this month began a yearlong study of how nutrients in retardants dropped in two big California fires affected reservoirs’ water quality.
Another study raises concerns that retardant encourages invasive plant growth.
Researchers in Montana in 2011 found that retardants dumped in wildfires in grasslands in the western part of the state altered the postfire landscape. They found “the abundance of exotic annuals and forbs increased dramatically” in certain settings afterward.
“By no means does this suggest that retardant should be not be used as a method for controlling wildfire, only that there may be an environmental cost to its use,” the study concluded.
Shaw agrees, calling the use of retardants a trade-off.
“The solution to this is to confront climate change in a more aggressive way,” Shaw said. “Our world is actually burning up. It’s getting hotter, with more drought and more violent weather.
