Wyoming Tanker Truck Explosion That Killed Driver Ruled Accidental

The death of a woman Saturday in a tanker explosion north of Wright, Wyoming, was accidental, the coroner has determined. The exact origin of the explosion of a tanker carrying hydrochloric acid is still under investigation.

Denice Downing 47, died at the explosion scene Saturday of head and chest trauma, Campbell County Coroner Paul Wallem told Cowboy State Daily in an interview Wednesday.

Downing’s autopsy was conducted Tuesday in Rapid City, South Dakota, said Wallem.

Wallem said he doesn’t know of any criminal investigation associated with the blast.

Campbell County Sheriff’s Office investigators are still working to determine the explosion’s origins, however, Investigator Josh Knittel told Cowboy State Daily on Wednesday.

At this juncture there are two predominant theories of origin, Knittel said: that the hydrochloric acid reacted to the tank itself, such as aluminum in it; or that there was a residue or sediment of some sort within the tank, that caused the reaction.

Authorities have sent the tank off for testing, said Knittel. 

He said the Occupational Safety and Health Administration (OSHA) has been investigating the scene alongside the sheriff’s office.

Oil Field Experience

Downing had been working for her current employer, a trucking company, for about a year, said Knittel. She had “several years of prior experience in the oil field,” he added.

Downing took her truck and trailer, loaded with hydrochloric acid, to the well site across from the Durham ranch, the investigator said. While the tank was being loaded a leak formed near the cab. People noticed it and tried to evacuate the area.

“She had come outside the truck, walked around to the passenger side, and around the time she got to the passenger side is when the tanker exploded,” said Knittel.

The back third of the tanker along with its axles shot southward about 30 yards, striking another vehicle and damaging it, Knittel said. The other two-thirds of the machine, including the bulk of the tanker and the cab, shot 70 yards northward, he added.

The cab separated from the frame and the engine. Knittel attributed this to the expansion pressure.

Fire Department

Sheriff’s investigators initially were unable to access the scene because of the hazardous materials. In hazmat suits, fire department personnel retrieved Downing’s body and decontaminated the area, said Knittel.

For this, the coroner was also grateful.

“Just want to thank the Campbell County Fire Department for their assistance,” said Wallem in his own interview.

Campbell County Fire Marshal Stuart Burnham did not return a Cowboy State Daily voicemail request for comment by publication time.

Though deputies couldn’t yet enter the scene, they studied it via drone video that day, Knittel said. He was also on scene Tuesday during a FARO scan of the site.

Clair McFarland can be reached at clair@cowboystatedaily.com.