Colorado report finds Aspen Acres Fire was sparked by tree falling onto power line

COLORADO — The Colorado Division of Fire Prevention and Control (CDFPC) has published the initial report on one of Colorado's most destructive wildfires since the Marshall Fire in 2021.

On Monday, the Scripps News Group acquired the CDFPC report from attorneys representing victims of the Aspen Acres Fire. According to the report, it began roughly 200 feet west of Colorado Highway 165 at mile marker 17, southwest of the intersection of Colorado Highway 165 and Custer Drive.

The report concludes that the fire was caused by an aspen tree falling onto a power line. The tree was blown over by high winds and fell on overhead power lines, investigators said. The impact of the falling tree forced the power lines down to about three feet above the ground.

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Evidence that the report uses to make its case includes eyewitness accounts, fire effects, fire patterns, and the actual aspen tree resting on a power line with burn marks.

Colorado Divisions of Fire Prevention and Control

The aspen tree trunk was in contact with both the hot and neutral conductor, according to the report. The tree also had visible heat damage where the tree was in contact with the lines, including charring and burn marks. The lines themselves also had arcing, melting, and charring, according to the report.

Colorado Division of Fire Protection and Control

The lines heated the tree bark and nearby vegetation to a point where they could ignite. Melted aluminum was also found under the area where the tree rested against the line, which should be considered as a contributor to the fire's ignition, the report said.

The report also provides evidence in the form of fire behavior and indicators, observed in the burn patterns. When burning in a particular direction, fire leaves signs of its direction of movement and its intensity. These patterns in the burned foliage, the report says, indicate that the fire advanced from the general origin area and spread west and south while also burning more intensely away from the origin area.

Other possible ignition sources were explored by investigators, including lightning, discarded smoking material, or an intentionally set fire.

Lightning was discarded as an explanation by investigators because they found that no lightning was recorded, no physical evidence of a strike was found, and no one reported lightning on that day. Not only that, a five-mile-wide report by STRIKEnet of the area found there were zero cloud-to-ground strikes detected by lightning sensors within five miles of the origin area.

Discarded smoking materials were discarded as an explanation because no smoking materials were found in the area by investigators. Additionally, investigators determined that the conditions in the area would make a fire caused by smoking materials "inconsistent and not viable given the data collected during this investigation."

Intentionally set fires do not necessarily mean arson — they simply include fires that were set intentionally and not necessarily maliciously. These include open flames like candles, matches, lighters, pilot lights, and oil lamps. However, investigators found that the fire did not originate anywhere near structures with open flames.

The ignition, which the report says took place in the general area of a series of utility poles, was also witnessed by a local resident at 5:45 a.m. on June 29. It immediately began to spread westward up the hill and towards the south, according to the testimony provided in the report.

The Aspen Acres Fire began on June 29 and remains active with 82% containment. It has burned 102,007 acres as of Oct. 2, according to the U.S. Forest Service.