Efforts Underway To Extinguish Long-Burning Coal Seam Fire In Colorado

Crews have begun a long-awaited project to extinguish a coal seam fire that has been burning underground on Marshall Mesa, south of Boulder, Colorado, for over a century. This persistent fire, which is a remnant of the region's coal mining history, has raised significant concerns about the potential for surface fires and threats to nearby communities. These worries have intensified, especially following the devastating 2021 Marshall Fire, which destroyed over a thousand homes.

The Colorado Inactive Mine Reclamation Program is set to lead the effort to eliminate this stubborn underground blaze. Located approximately 30 feet underground, crews will excavate down to the coal seam, which is between 6 to 8 feet thick. The plan involves bringing the smoldering material to the surface, mixing it with cooler soil to prevent reignition, and then reburying it.

"This is an attempt to completely excavate and extinguish all areas where we've seen previous fire activity and where there's additional coal that's unburned," stated Jeff Graves, the director of Colorado's Inactive Mine Reclamation Program. The project is expected to take three to four months and will also include renovations and expansions to the Marshall Mesa trailhead and parking lot, alongside installing a 20,000-gallon cistern to improve fire resilience for nearby homes.

The Colorado Division of Reclamation, Mining and Safety, which oversees the Inactive Mine Reclamation Program, has been contacted for updates regarding the excavation's progress. With approximately 40 other underground coal fires remaining in the state, the Marshall Mesa fire is considered one of the more accessible and manageable sites, making it a priority for extinguishment.

Graves explained that various methods can ignite coal, the most significant being spontaneous combustion due to exposure to oxygen over time. This continues to heat the coal until it ignites. In addition to this, past practices like miners tipping over candles, lightning strikes, and wildfires can also set off underground fires.

Once ignited, these coal fires can reach temperatures of up to 1,000 degrees, creating the potential for surface fires, as seen in a previous incident in 2005. Although there was speculation that the 2021 Marshall Fire could have originated from an underground coal fire, investigations by the Boulder County Sheriff’s Office and District Attorney's Office concluded this was unlikely, although it couldn't be entirely ruled out.

"It's in an area that has high risk to infrastructure and is one of those fires that's relatively easy to attack and hopefully extinguish," Graves remarked. Once the Marshall Mesa fire is extinguished, Boulder County will be free of any remaining underground coal fires, as a similar project was recently completed near the intersection of Cherryvale and Marshall roads.

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