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The Marshall fire burns in Boulder County on Dec. 30, 2021. (Jeremy Sparig, Special to The Colorado Sun)

BOULDER — Embers buried for six days on a residential property reignited and together with sparks from an “unmoored” Xcel Energy power line started the 2021 Marshall fire in Boulder County, the sheriff said Thursday morning.

A residential fire Dec. 24 to burn scrap wood and tree branches resurfaced because of the winds Dec. 30, Boulder County Sheriff Curtis Johnson said. The sheriff said the fire was put out “responsibly” Dec. 24 when it was buried. But around 11 a.m. on Dec. 30, high winds, pushing 100 mph, resurfaced embers and blew them into dry brush at 5325 Eldorado Springs Road.

A second fire was likely started an hour later that day by Xcel Energy power lines and also quickly spread, Johnson said. At some point the two fires combined, though the investigation did not focus on what time or where they merged.

The district attorney’s office determined there was “insufficient or no evidence of a crime” and no reason to file charges, Boulder County District Attorney Michael Dougherty said.

“If we were to tell you today that we were filing charges it would be wrong and unethical,” Dougherty said. “We can only file charges if there’s evidence of a crime being committed.”

Sheriff Curtis Johnson reviews possible causes of the Marshall fire. He is flanked by images from what he called the two most probable sources: an unmoored Xcel Energy power line and a scrap wood fire that started Dec. 24 at a nearby residential property. (Parker Yamasaki, The Colorado Sun)

Dougherty said investigators found no evidence of negligence or recklessness by Xcel. Rather, high wind caused a power line to disconnect from its mooring and contact other lines, leading to electrical arcing and hot particles showering onto dry grass. 

There were no known problems with the power line prior to the fire, Dougherty said. 

“This is a different discussion and a different decision, if that wire was worn or shoddy or they had maintenance issues in the past. There was no such record of that, no indication of that.”

An Xcel Energy spokesman said Thursday that the company disputes that its power lines caused the second ignition. He said the utility has reviewed its maintenance records and believes the system was properly maintained.

“We strongly disagree with any suggestion that Xcel Energy’s powerlines caused the second ignition, which according to the report started 80 to 110 feet away from Xcel Energy’s powerlines in an area with underground coal fire activity,” a company spokesperson said in a statement. “Xcel Energy did not have the opportunity to review and comment on the analyses relied on by the Sheriff’s Office and believes those analyses are flawed and their conclusions are incorrect.”

A group of more than 20 victims of the fire filed a new lawsuit Thursday against Xcel. They lawsuit says Xcel “was negligent in its operation of its power lines and equipment in that (the company) unreasonably failed to maintain, monitor and/or supervise its property in a manner so as to prevent an arcing event from causing a fire.”

The new legal action is separate from a lawsuit filed against Xcel in April 2022 by two business owners and a couple. That legal action, before the investigation into the Marshall fire was complete, alleged Xcel’s power lines and equipment were a “substantial factor” in the cause, origin and continuation of the wildfire, which was fanned by intense winds. In November a judge denied Xcel’s motion to dismiss that lawsuit.

New details on the investigation come nearly 18 months after the fire exploded and raced across 6,000 acres, pushed by gale-force winds across parched grassland into subdivisions bordering open space. Two people died in the fire and more than 1,000 homes and businesses were destroyed in Louisville, Superior and unincorporated Boulder County. Johnson estimated the losses at $2 billion. An estimated 1,000 pets also died as homes burned to the ground.

In addressing the disastrous toll, Johnson, who lost his own home to the fire, choked up and thanked the community for its patience as the investigation played out. 

“I know personally the last 18 months have been hard and not having answers creates stress and challenges that we don’t need,” he said, his voice quavering. “And I hope that now we can focus on rebuilding our lives and getting back to our homes and our community.”

The Boulder County Sheriff’s Office said the fire likely started near Marshall Road and Colorado 93, but federal agencies aided in its investigation to try to pinpoint the cause of the fire. 

A photo exhibit (left) shows a fire on the residential property at 5325 Eldorado Road on December 24, six days before the Marshall Fire. An investigation found that embers from this fire were uncovered by high winds on Dec. 30, ultimately sparking one of two fires that led to the Marshall fire. (Parker Yamasaki, The Colorado Sun)

The sheriff’s office consulted with outside labs, fire investigators with the Forest Service and a private electrical engineer throughout the investigation. It also reviewed 146 reports of missing people, conducted two death investigations, reviewed 200 tips from the community, executed several search warrants and interviewed hundreds of victims and witnesses. 

Conditions were cool and damp when the property owners at 5325 Eldorado Springs Road, the Twelve Tribes religious group, started burning a pile of debris on Dec. 24, investigators said. There was no significant wind and by 5 p.m. they had the fire covered with dirt.

The Twelve Tribes religious community’s compound at 5325 Eldorado Springs Drive in the unincorporated town of Marshall in Boulder County is shown in this Jan. 9, 2022 photo. (Mike Sweeney, Special to The Colorado Sun)

Firefighters who were at the compound that day felt they were burning responsibly, noting a swimming pool on the property. 

Investigators and trained forensic child examiners interviewed the 40 people who lived on the property. They determined that there was not enough evidence to prove that anyone on the property disregarded substantial and unjustifiable risk — a requirement for criminal charges — when they started the Dec. 24 burn. Nor did they set new fires on Dec. 30.

Buried embers can smolder for weeks, even months, after they are buried, Dougherty said, and the property owners “had no idea” that the wind would reach hurricane force days later. 

“They had no idea that this could spread and destroy over 1,000 homes,” he said. Once they realized the fire was burning on Dec. 30, they tried to put the flames out but the fire quickly spread.

The shed on the property was not on fire when firefighters arrived, despite early rumors the fire started there.

A representative of Twelve Tribes couldn’t immediately be reached for comment.

The second fire started near the Marshall Mesa trailhead, about 2,000 feet southwest of the first fire. Investigators said it was unlikely that embers from the first fire could have traveled that far, against wind blowing west to east at sustained speeds of 50 mph. 

A trail camera captured footage of an unmoored powerline in the area, authorities said. 

A separate report of a downed line near Colorado 93 and Eldorado Springs Drive turned out to be a communication line, which did not have enough electrical current to start a fire, according to the investigation. 

Experts ruled out coal seams as a likely cause of the fire, Johnson said, because significant mitigation work was done after a surface vent from an underground coal fire ignited a small grass fire in 2005.  

After 275 tons of material was dumped into the area, the temperature of the air from the coal vents was below 90 degrees, compared with 373 degrees prior to the mitigation. After the Marshall fire, experts tested the temperatures again and said there was no indication that temperatures coming out of the vents were high enough to cause a fire. 

Boulder County strengthened its ordinances last year to provide specific guidelines on how to fully extinguish fires.

Documents detailing the Marshall fire investigation were posted on Boulder County’s website Thursday afternoon.

Johnson said he expected the lack of criminal charges to bring mixed reactions from members of the community, some who are on a path moving forward and others who are “still struggling to make it to tomorrow.”

“I know that ultimately sometimes really bad things happen and I was caught up in that. My home was lost, but I’m moving forward, because, for me, it’s very important to reclaim my life after the fire,” he said. “And the only way I feel that I can do that is to rebuild my home, plant my flag, and get back in my neighborhood.”

Colorado Sun reporter Parker Yamasaki contributed to this story

Olivia Prentzel covers breaking news and a wide range of other important issues impacting Coloradans for The Colorado Sun, where she has been a staff writer since 2021. At The Sun, she has covered wildfires, criminal justice, the environment,...