BOULDER COUNTY, Colo. – A coal fire that burned beneath Boulder County for over a century has finally been extinguished.
The fire, located under the Marshall Mesa trailhead, marks a significant milestone in Colorado’s efforts to address its numerous underground coal fires.
The site, one of the estimated 14,000 abandoned mines across Colorado, had been smoldering since the early 1900s.
According to Tara Tafi, senior project manager with the Colorado Division of Reclamation, Mining, and Safety (DRMS), records indicate that fires were burning in some of these mines even while they were active.
The Marshall Mesa site, now part of Boulder County Parks and Open Space, had little visible or olfactory evidence of the fire. “You didn’t smell it on-site,” Tafi said.
Despite this, questions arose about its potential connection to the devastating Marshall Fire of 2021, which destroyed over 1,000 homes. While no direct link was established, the incident highlighted the risks posed by underground coal fires in Colorado.
Federal Funding and Mitigation Efforts
In 2022, Colorado received funding through the Bipartisan Infrastructure Deal to tackle its underground coal fire problem.
The state currently monitors about 40 known coal seam fire sites, though not all can be extinguished due to geological challenges. However, the Marshall site presented a rare opportunity for complete mitigation.
“This site was uniquely accessible, which allowed us to implement a full excavation and extinguishment strategy,” Tafi explained.
Excavation and Restoration
The mitigation project began in November 2024 and required heavy excavation over 12 acres. Crews dug down 30 feet to expose and break up the coal seam, mixing it with rock and soil to prevent reignition. “We’ve now removed all remaining coal resources from this area,” Tafi confirmed.
In the final phase of the project, crews are grading the landscape to restore its natural contours and prepare it for future use.
Project manager Jeremy Reinieke noted, “We’ll re-contour it to match the surrounding topography and make it as park-like as possible.”
Residents and park visitors have expressed relief and optimism about the project’s impact on fire mitigation. “People are glad to see concrete actions being taken to address this long-standing issue,” Reinieke added.
Future Projects
After completing the Marshall site in February, the DRMS will turn the area over to Boulder County, which will rebuild trailhead infrastructure.
Meanwhile, the DRMS is already planning two additional projects in Fremont County and Craig to address other underground coal fires in 2025.
This success at Marshall Mesa highlights Colorado’s ongoing commitment to mitigating the risks posed by its abandoned mines, ensuring safer communities and preserved natural spaces.
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