The two largest wildfires in Colorado history, which sparked within the past few months, are seeming to defy logic as they continue to burn while surrounded by snow. With recent precipitation, including snowfall that blanketed both fires, why aren't they extinguished yet?
The 208,913-acre Cameron Peak Fire in Larimer County and 193,812-acre East Troublesome Fire in Grand County are still considered active fires, though that activity is minimal. Neither is contained — the Cameron Peak Fire's containment level is 92% and the East Troublesome Fire's is 72%.
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Maribeth Pecotte, acting public information officer at the East Troublesome Fire, explained that fire is likely still smoldering inside, underneath or even underground some fuels.
Fire that is smoldering underground is a concern because it can burn trees' roots and the inside of the trunk, while jumping underground from root system to root system, she said.
“Fire can actually go underground when conditions get wet on top," she explained. "It will start burning down into the roots and the stumps of the trees. It gets down in there. And if that snow were to melt away and the moisture dry up — if it gets a little bit of oxygen, it can come back to life.”
She said fire officials aren't seeing smoke from the ground of the East Troublesome Fire, but an aerial crew can use thermal imaging to spot hidden pockets of heat.
“Based on weather and shortening days, it’s unlikely that it’s going to rear its head and become active again," Pecotte said. "With that said, weather could become warm and dry, and if we have warm, dry and windy (conditions) for a period of time, that could breathe it back to life.”
She noted the Fern Lake Fire in Rocky Mountain from October 2012, which reignited in December and wasn't completely extinguished until the following July. The kind of forest burned in the Fern Lake Fire is the same as the East Troublesome Fire — same topography, terrain, forest conditions, Pecotte said.
However, the area around the 2012 Fern Lake Fire had gone hundreds of years — more than 800, according to RMNP — without a fire because of its subalpine ecosystem. Fire isn't a "frequent visitor" there, Pecotte said. The area had a lot of decomposed unburned fuel, also called "duff," which was smoldering as deep as 15 to 20 feet underground.
If a fire gets down that deep, it can stay insulated from the cold and moisture. Should it get a breath of fresh air, it can rise to the surface and come back to life, she explained.
“We look to that as an example of what can happen," she said.
She explained that's why firefighters dig trenches along containment lines — they're scraping away the DUF to get to mineral soil.
More winter weather will likely completely extinguish the East Troublesome Fire, Pecotte said, but it will take more than the storms that have occurred so far.
Bethany Urban, public information officer with the Cameron Peak Fire, explained fires that burn as large and hot as the one in Larimer County need a true season-ending event to consider them out.
"This year, weather-wise, we had a really interesting pattern where, as you can see from the history of this fire, we got wind, we got snow, and then it quickly melts and dries out and conditions are right for burning again. And then we get wind and snow and then it quickly dries out and we get conditions right for burning again," she said.
There is still the possibility of warmer and drier conditions at the fire, but she said fire officials are not expecting any significant fire spread.
Firefighters still spotted a few minor smoke trails on Monday, she said. Some of that may be from heavy, large-diameter logs or stumps that still have heat in them and are smoldering, especially in the Pingree Park area. The snow around these fuels is keeping the fire where it is, Urban said.
She said helicopters have been dropping water on the areas where smoke is spotted, though they couldn't fly Monday or Tuesday due to weather conditions.
Both fires will likely continue burning, however minimally, until there is enough sustained precipitation to keep the ground damp and fuels wet, when "conditions are no longer friendly for burning," Urban said.
Both the Cameron Peak Fire and East Troublesome Fire have left behind soil that doesn’t hold root systems well and weakened trees— a combination that makes trees in the burn area likely to fall. Come spring, landslides and runoff will be a concern, Urban said.
“Overall, fire does create the potential for soil erosion, which is one of the reasons we focus so hard on rehabilitation after the fact — to try and lessen impacts to the soil, whether it’s by the fire or by our suppression efforts," Urban said. "We try to restore those areas so the soil will absorb water more and make it less likely for runoff, mudslides and those types of things.”
Pecotte said officials at the East Troublesome Fire are using the expertise of a burn area specialist to help stabilize the soil and prevent it from sliding come spring.