What started the Marshall fire? Boulder County set to announce findings of 17-month investigation

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Boulder County’s sheriff and district attorney on Thursday will announce the findings of their investigation into the origin of the deadly Marshall fire in late 2021.

A news conference is scheduled for 10 a.m. at the Boulder County Sheriff’s Office, but no hint of what will be announced has been given. A media advisory says Sheriff Curtis Johnson and District Attorney Michael Dougherty will speak on “the investigative outcome into the cause and origin of the 2021 Marshall fire.”

The Dec. 30, 2021, wildfire was the most costly in Colorado history, destroying more than $2 billion in property. Two people died in the fire, and more than 1,000 homes and businesses were destroyed in Superior, Louisville and unincorporated Boulder County. The fire burned across 6,000 acres as it was fueled by hurricane-force winds and dry grass and brush.

Since the fire’s start, speculation around the cause has wavered between multiple theories. It is believed to have started near the intersection of Marshall Road and Colorado 93.

On the day of the fire, then-Sheriff Joe Pelle said it might have been caused by power lines blown down by the high winds. He reversed course the next day and said there was no evidence that power lines had sparked the wildfire. Instead, Xcel Energy told authorities its inspections found compromised communication lines that may have been misidentified as power lines.

In April 2022, however, two businesses and an anonymous couple filed a lawsuit that claims Xcel Energy’s power lines did cause the Marshall fire. The lawsuit accuses the power company of failing to maintain and monitor its lines. Xcel asked a judge to dismiss the lawsuit, but he ruled that it could move forward.

Ron Mostek, a subcontractor for Xcel Energy, uses a utility locater to look for gas and electric lines amidst the rubble of homes that burned to the ground in the Coal Creek Ranch subdivision in Louisville in the aftermath of the Marshall fire on Dec. 31, 2021. (Photo by Helen H. Richardson/The Denver Post)

Days after the fire, the Boulder County Sheriff’s Office fenced off property and executed a search warrant on land owned by the Twelve Tribes, a nationwide religious cult. A neighbor took video on the day of the Marshall fire that showed a shed burning on the property, and that video circulated online as people looked for someone to blame. Law enforcement never reported what investigators found on the property.

Finally, investigators looked at the possibility that an underground coal seam that has burned for nearly a century under Marshall Mesa somehow ignited the fire. The sheriff’s office hired outside help to look into that possibility.

In March, Johnson, who lost his home in the fire, told a packed town hall meeting that the investigation was a month or two from completion. At the time, he said new evidence continued to emerge and that investigators would take their time.

Evidence includes hundreds of videos and pictures taken by law enforcement body cameras as well as drone footage. Investigators also have reviewed photos and videos taken by witnesses.

In December, the sheriff’s office posted footage online of its rescue efforts in the burn zone east of Cherryvale Drive online. All footage from operations west of Cherryvale Drive has been kept secret.


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