State to mitigate underground Lewis Coal Mine Fire in Boulder County…

The state plans to start mitigation work this fall on the underground coal mine fire at the Lewis site, located northeast of the intersection of Marshall and Cherryvale roads in Boulder County.

While monitoring the site, the Colorado Division of Reclamation, Mining and Safety recently observed increased activity from the smoldering coal seam fire, which has burned for more than 50 years, according to a news release.

“The Colorado Division of Reclamation, Mining and Safety Lewis Coal Mine Fire Mitigation Project is a proactive effort to reduce the potential for surface ignition as a result of the increased underground coal mine fire activity. Additionally, the work will help protect the water supply ditch on site,” Jeff Graves, the director of the state’s Inactive Mine Reclamation Program, wrote in the news release.

Increased activity that was observed includes increased surface subsidence, surface fracturing and cracking; higher surface temperatures; increased venting and gas emissions; and stressed vegetation. The state also observed conditions that are damaging to the Davidson Ditch, which increase the chance of flooding.

The Lewis Mine site is partially located underneath the Davidson Ditch, which supplies water. To complete the work before the ditch fills with water in the spring, mitigation must begin this fall. To allow that to happen, Boulder County is set to issue an emergency declaration Tuesday to acknowledge the potential dangers of the site.

“Boulder County welcomes the state’s efforts to proactively address potential fire and flood risk caused by the underground coal mine fire at the Lewis site,” Boulder County Community Planning and Permitting Director Dale Case wrote in the news release.

The county and the Reclamation, Mining & Safety division also are hosting an online information session from 5:30 to 6:30 p.m. Aug. 28 to answer resident questions. The online session will be hosted in English. A recording of the meeting, along with a Spanish transcript, will be available on YouTube.

To attend the online session, register at tinyurl.com/8kud2rrd.

The mitigation effort will require excavating about 30 feet to just below the coal mine workings and removing any burning or smoldering coal, according to the news release. The coal then will be blended thoroughly with rock or soil.

The temperature of the blended material will be monitored until it’s lower than 100 degrees, according to the news release. While the material is exposed, the state will monitor the piles and employ measures to ensure the safety of surrounding area, according to the news release.

Finally, the extinguished material will be returned and graded to match adjacent natural contours and revegetated with native vegetation.

The Lewis Mine site is located in unincorporated Boulder County about one mile south of Boulder, underneath two private properties. The property owners are supportive of the state’s mitigation project, according to the news release.

Recent testing and ongoing monitoring indicated lesser fire activity at the nearby Marshall coal mine fire, which is located near and under Boulder open space, according to the news release. Following the devastating Marshall Fire in late 2021, the city of Boulder — which owns most of the property involved — asked the state to further examine the Marshall coal mine fire.

Mitigation work on the Marshall coal mine fire is tentatively scheduled for next year, while the state continues to monitor the site, according to the news release.