Colorado crews plan to mitigate second underground coal mine fire near origin of Marshall Fire

State mine safety teams are moving forward with plans to uncover a second active underground fire later this year in the area where the most destructive wildfire in Colorado history ignited .

The Marshall Fire destroyed more than 1,000 homes on December 30, 2021. It was pushed by 100 mph winds through open spaces and into the communities of Superior and Louisville. Two residents were killed there.

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Authorities, after an 18-month investigation, determined there were two ignition points: the first was a smoldering wood pile on private property, the second under power lines. This last point is controversial, with Xcel Energy disagreeing with the investigators' conclusions. The company is fight litigation accusing its lines of being at least partially the cause of the fire.

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The investigation did not rule out the possibility that coal burned underground for decades contributed to the fire. Winds as strong as those felt during the Marshall Fire could likely draw heat from underground coal fires to the surface.

One of these sites contains the Lewis Mines which were abandoned and buried in 1946. A surface vent emitting heat measured at 120 degrees was discovered in 2018.

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Colorado Division of Reclamation, Mining and Safety Teams started a redesign from the Lewis mine site in January. Excavators carefully excavated the land adjacent to the Davidson Ditch, alternately digging and filling 10-foot “fingers” of steaming soil to keep the concrete irrigation canal from collapsing.

Crews dug 30 feet deep and encountered temperatures as high as 600 degrees. When temperatures rose above 90 degrees, crews mixed the heated soil with fresh dirt and rocks until temperatures dropped below that mark.

The project was completed in early April, ahead of schedule.

Crews now plan to shoot 2,000 feet above the Marshall Mines, a DRMS ​​spokesperson confirmed. The department is currently in the permitting process with Boulder County since the project, expected to begin later this summer or fall, will affect access to county open space at the Marshall Mesa trailhead.

This will be the second time mitigation efforts have been undertaken at Marshall Mines. A vent from the mines was blamed for starting a small bushfire in 2005. Three years later, 275 tons of rock were dumped on the site, increasing its surface area by 18 inches.

Lewis Mines' recent mitigation measures cost $316,002, according to department spokesperson Chris Arend. Marshall's mitigation measures will be implemented now that additional federal funds have been received by the department to combat coal mine fires across the state.

In a 2018 DRMS ​​study, there are 1,736 abandoned coal mines in Colorado. A contractor hired by the state to examine them found that 38 were actively burning or dormant and extinguished after previously burning.