The 2018 Burro Fire that torched 4,600 acres of the San Juan National Forest northeast of Dolores and cost more than $3 million to fight, was likely human-caused, according to a completed investigation.

A 50-page report of the investigation by the national forest and the Montezuma County Sheriff’s Office was released to The Journal this week by Sheriff Steve Nowlin. The Journal also made repeated requests for the report to the Dolores Ranger District office of the national forest.

The Burro Fire was first reported June 8 in Bear Creek Canyon, and its origin was placed on the Gold Run Trail, which enters the canyon from the southwest.

“The cause of the Burro Fire is likely associated with human activity along the Gold Run Trail,” said National Forest investigator Lathan Sidebottom.

Investigators have not identified a suspect or ignition source, and they reported no evidence of a lightning strike in the preceding seven days.

According to investigators, possible causes of the fire include motorized equipment, smoking and the reckless or intentional use of an incendiary device.

The fire’s origin was placed about halfway down the 2.2-mile Gold Run Trail on a 75-square-foot bench that trail users might use for a shaded break.

Multiple interviews with people in the area June 8 “failed to establish the known presence of any particular person in the origin area that day,” Sidebottom stated in the report.

“Due to the lack of discovery of a specific point of origin, ignition source or firsthand witness statements as to the definitive events, the precise cause is undetermined,” he stated. “The investigation will continue if new leads are developed.”

The investigation contained interviews from people including 12 witnesses and two other parties that reported the fire in its early stage.

It pieced together a timeline of who was where when the fire started. Potential ignition causes were either ruled out or deemed a possible cause. Because of the intensity of the fire and fallen trees, the area of the initial fire at Gold Run was not examined until June 20.

The Burro Fire started June 8 and burned 4,593 acres in rugged Bear Creek canyon area before it was contained Aug. 1. The firefight cost $3.3 million. There were no structures lost, and no serious injuries. It burned at the same time as the 416 Fire in the Animas Valley to the east. At one point, both fires nearly merged, coming within a few miles of each other around Indian Trail Ridge. The extreme fire danger triggered a closure of the San Juan National Forest from June 12 to June 20.

On June 20, Sidebottom, federal law enforcement officer Shawn Cave, Fire Prevention Technician Dan Zinn and two members of the Montezuma County Sheriff’s Office began their analysis of fire patterns in the origin area.

Based on burn patterns and witness accounts, they determined an area on a gently sloping bench to be the likely origin of the fire, but a specific point could not be identified. A search failed to locate an ignition source or evidence of lightning strikes.

The bench lies adjacent to the Gold Run Trail under a thick, shaded canopy after descending a steep, sunny and rocky area.

“The sun shelter from tree canopy and more level terrain creates an ideal stopping point for users of the trail,” according to the Forest Service investigation. “Due to the terrain features, lack of other viable ignition sources and observed indicators, the cause of the fire is likely related to some undetermined human activity with use of the trail.”

The fire’s movement supports that theory because there is evidence that vegetation burned uphill there, then broke free of the soil and rolled downhill, spreading fire as they tumbled.

Farther downhill from the bench, investigators found a tomato juice can, a small camping fuel container that appeared to have burst during the fire, and a piece of leather strapping possibly used as equine equipment.

However, because no evidence indicated that fire spread from where the items were discovered, they were ruled out as points of origin.

By process of elimination, investigators determined three possible causes: motorized equipment use, smoking and incendiary device.

Equipment use: The Gold Run trail is open to motorcycles, which can transfer heat with exhaust, brakes, sparks, friction, mechanical breakdown and fluid leaks. However, facts and circumstances do not support motorcycle use as a likely cause.First, rainfall after the fire prevented an accurate analysis of motorcycle traffic on the dirt trail.

Second, a motorcycle’s descent on Gold Run Trail, typically used to access Bear Creek, would not expel the exhaust carbon that is typical of uphill use. No tire spin or rut was found that would indicate a high-revving uphill climb.

Smoking: A cigarette, pipe or cigar could have also ignited the fire, the report speculates, along with lighters or matches. However, wildfires caused by smokers can be hard to determine because of fragile evidence.According to the report, “While no physical evidence of smoking was observed, the presence of human activity in the area and dry environmental conditions could lead to a smoking-caused fire in limited circumstances.”

Incendiary or arson: Reckless or intentional fires can be determined if there is a pattern of suspicious fires in a known area. In this case, there is no recent identifiable pattern of arson in the area. No physical evidence suggested an intentional ignition, but it was not ruled out.Causes that were excluded were lightning, firearms, debris burning, campfire, fireworks, power lines, exploding targets, spontaneous heating, refraction from glass, flares and flying lanterns.

Two outfitter groups – Deer Hill Expeditions and Open Sky Wilderness Therapy – were present in the Bear Creek area on the afternoon of June 8 but were cleared of involvement.

Interviews placed them away from the area of origin at the time.

Deer Hill, which was conducting staff training, had hiked down the Gold Run trail to the Bear Creek trail June 6, two days before fire started. Open Sky Wilderness Therapy had two client groups in the area but hiked up nearby Burro Mountain and did not use the Gold Run Trail.

Both groups witnessed the initial column of smoke June 8 and called company officials, who then relayed the information to forest officials. The groups evacuated.

A mountain biker who left a message about the fire and took pictures of vehicles in the area also was interviewed. The vehicles’ license plates were checked out by law enforcement and found to belong to the outfitters. Unidentified hikers were seen on Bear Creek trail the day before the fire but were a significant distance from the fire’s origin.

The investigation revealed no suspects, but by excluding natural causes, human cause was considered likely. Officials noted that forest use was heavy when fire started; for example, 55 campers were at the Twin Lakes area.

“During evacuation, we were surprised how many people were out there,” said Dolores District Ranger Derek Padilla.

The extreme fire danger, combined with drought and other wildfires nearby, led to the first-ever, forest closure, he said.

As far as lessons learned from the fire, Padilla said preseason planning due to drought conditions and wildfire potential paid off, and led to a timely response with adequate resources.

For the public, the lesson is that fire has the potential to spread even at high elevations.

“It is important to be cautious with fire no matter how safe you think it might be,” Padilla said. “Also, be observant, a member of the public may be the key to determining who or what may have started the fire.”

The Burro Fire was first reported to Montezuma County Dispatch from a local resident 911 call at about 3 p.m. June 8, according to the investigation. At 3:48 p.m., a Flight For Life helicopter passing over Bear Creek located the fire.

jmimiaga@the-journal.com