THOMASTON, Maine — The explosion at Dragon Cement that rocked the midcoast area last week was accidental in origin, according to an investigator from the Maine State Fire Marshal’s Office.
“The cause was actually a smoke explosion,” Sgt. Ken Grimes said Wednesday.
He said the explosion occurred about noon Dec. 23 as a four-person demolition crew from a Massachusetts company called RubbleMakers was working to dismantle a large, empty tank located on the western end of the Thomaston cement plant.
“While cutting material away from the outside of the steel storage tank, sparks ignited a big debris pile on the ground,” Grimes said. “The hot gases and smoke, while that debris pile was burning, went inside the tank.”
The demolition workers climbed down from the tank and were trying to put out the fire in the debris pile, which was made of normal construction materials including wood, foam and fiberglass insulation.
This may have saved them from injury, Grimes said, adding that when the particulate — or smoke — matter inside the tank was sufficiently heated, it combined with oxygen with explosive results.
“[There was] a rapid, simultaneous combustion of the smoke particulate,” Grimes said. “The force of the blast went up through the top of the tank. It was quite substantial.”
In fact, the blast blew off the round fiberglass stack at the top of the tank, and propelled it hundreds of feet away. The force also shattered windows in Dragon Cement’s main office building, although Grimes said that he did not believe the building had any structural damage.
No one was in the office at that time because there was a company Christmas party on the other side of the plant.
“There was a lot of flying glass,” Grimes said. “There was certainly the possibility of a glass shrapnel effect.”
The blast was heard as far away as Damariscotta and Belfast, according to anecdotal reports.
Grimes said that while demolition workers interviewed after the explosion seemed OK, he imagined being so close to the blast was “a bit unnerving.”
Because initial information received by his office was “so sketchy,” four investigators raced to Thomaston, Grimes said. After hearing that there was a building explosion at Dragon Cement, investigators weren’t sure if they would need to interview injured people or emergency aid workers.
Ultimately, investigators will submit an official report on the blast, but Grimes said they completed their interviews and fieldwork that day.
“It’s extremely unusual to have something of this degree occur,” he said.