It was late morning when the call came in to the – 11:44 a.m., to be exact.
A truck had hit a valve at the former SolidWorks site at 300 Baker Avenue, and an underground propane tank was leaking. Upon arrival the engine company found a small leak from a damaged valve. An investigation revealed the valve was badly damaged, with propane leaking from its many fractures.
The building company, Normandy Real Estate Partners, called in the gas company, Eastern Propane, who determined to locate an evacuation valve to unload the product—about 250 to 300 gallons of liquid propane from a 500-gallon tank—but, as it turns out, there wasn’t a valve.
The tank itself wasn’t particularly large, but propane’s expansion ratio is 270:1, and so that 300 gallons could expand very quickly, Concord Fire Chief Mark Cotreau explained Monday evening, about seven hours after the leak was first reported.
“The concern for the fire department is leak potential,” the chief said at the scene, “Because of that, we had to take the situation very, very seriously.”
With no evacuation valve, the best available option was to do a “flame off,” or controlled burn, according to Cotreau.
It was late afternoon when the burn began. Estimates said it would take about 8 to 11 hours to complete from the start of the burn off, which was around 4:45 p.m. Firefighters expected to remain on the scene through the night.
The scene was the corner of the large parking lot of an industrial park in transition. On one side of the leaking tank, new construction is rising from the pavement. And on the other is renovation work to the former SolidWorks site, in preparation for the next tenant.
According to Cotreau, a handful of people were evacuated from the construction sites, while those at the other end of the building were appraised of the situation and told they’d be expected to evacuate should an alarm activation. Yellow fire line cordoned off the area surrounding the leak and burn, and red fire apparatus formed a perimeter around that.
“There was a fair amount of danger associated with the situation, and the biggest was from the potential release,” Cotreau said Monday evening. “So we took up a defensive position to protect the building, the people and the workers near the valve.”
By about 7 p.m., mutual aid, which came from Bedford, Lincoln and Hanscom Air Force Base, had cleared the scene. Meanwhile, Acton and Sudbury covered Concord’s two stations. In addition to mutual aid, CFD called in all off-duty personnel and the Mass Department of Fire Services Rehab Unit was also on the scene.