Explosion, Fire at LPG Mixing Plant Threatens Several Major Exposures
An explosion at an LPG mixing plant in St. Johnsbury, Vt., shattered a fourbrick-thick building and broke a 2-inch supply pipe. Escaping LPG vaporized and ignited, sending flames up to 80 feet in the air. Arriving fire fighters set up to protect several major exposures.
The St. Johnsbury Fire Department and Chief Jerald Fournier responded to the mixing plant at 12:49 a.m. last July 26, a Sunday. Approximately four minutes before, city police had been alerted to a possible problem at the plant by a direct alarm between the mixing plant and police headquarters. Officer June Kelly was en route to investigate when the explosion shook the surrounding area, showering adjacent South Main St. with brick and debris and blowing in windows of about 12 residences.
The plant, operated by the Gas Company of Vermont, mixed propane vapor with air to reduce the heat output from 2500 Btu per cubic foot to the 700 Btu level that was normal for customer appliances. A combination of thick brick walls and thin wooden roofing was believed able to contain any concussion, sparing adjacent residences.
At the Vermont State Police barracks less than a mile away, a trooper was just returning from patrol when a brilliant flash lit his rearview mirror. In one motion, he floored the cruiser in a Uturn and radioed his dispatcher. As a result, three state police officers were reportedly on the scene blockading access roads within four minutes of the explosion.
—photos by the author.
“Our initial response was a 750-gpm pumper, a 75-foot aerial, and four men,” said Fournier. The department was staffed by 15 pajd and 15 call fire fighters. “We had preplanned the building and were aware of a number of critical exposures in addition to immediately adjacent residences that state troopers and sheriffs deputies were already evacuating.”
Exposures of first concern to fire fighters included a full 30,000-gallon LPG rail tank car sitting on a siding 60 feet from the blaze, a 30,000-gallon stationary aboveground LPG tank approximately 40 percent full sitting 75 feet away, a 16,000-gallon LPG tank estimated to be 40 percent full situated within 100 feet, and a 16,000-gallon tank of propane gas located within 20 feet of the fire. Additional exposures included a second building containing 100-pound, household-type cylinders and a third used to store company vehicles.
“Our initial action—after calling the railroad that runs a 24-hour switching operation in the adjacent yards and asking them to immediately remove the loaded LPG tank car—was to get water on the tanks to keep them cool,” said Fournier. “There did not appear to be too much danger to these tanks at this time even though they were quite close to the fire. Flames fed by vaporized LPG escaping from the ruptured 2-inch pipe were spectacular, but they were going straight into the air as there was almost no wind. We purposely refrained from any attempt to extinguish the burning, leaking gas so we would not have to contend with an accumulation of explosive vapors while gas company technicians were en route to shut down the valves.”
Covered exposures
“We immediately got a 2 ½-inch line on the 30,000-gallon stationary tank and established a deluge set-up to cover the railroad tank car,” added Fournier, “then positioned additional lines for coverage of a 16,000-gallon propane tank and other exposures. Within five minutes of arrival we called for two additional pumpers, a 1000-gpm and a 750-gpm.
“The first of these additional units laid approximately 1200 feet of 2 ½-inch line to the scene, then went back and hitched to a hydrant to service one hand line and one line to the deluge set-up. We then laid two more lines off the 1000-gpm pumper, one for a hand line and a second line to the deluge apparatus. A 750-gpm pumper made two 1600-foot lays to a hydrant and then pumped in tandem with the original 750-gpm pumper located 1200 feet nearer the scene.
“A railway crew moved the 30,000gallon tank car to safety, and gas company technicians by then had shut off the flow of escaping LPG,” Fournier said. “As soon as the gas was shut off, the remaining fire was not serious. The mixing plant had been nearly all brick and steel except for a light wooden roof, and combustibles within the building were limited to a few stored tires and some bags of coal left over from the days when the plant had manufactured gas from coal. Once the gas was shut off, we were able to bring the remaining fire under control within an hour.
Good water
“Basically, we were able to get good water, and there was almost no wind. Also, there was tremendous, instantaneous response from state and local police and sheriff s deputies who immediately closed off access to the area and began house-by-house evacuation.”
Although a dozen frame residences lining the road across from the gas plant had many of their windows and a few doors blown, there was no fire damage other than to the exploded mixing building itself. LPG and propane tanks as close as 20 feet to the fire later showed little or no readily apparent heat or flame damage, although one tank buckled slightly from the weight of falling debris and necessitated precautionary repairs later in the day.
The Vermont State hazardous materials one-call system was activated by state police, primarily to secure additional gas detectors plus the services of a gas systems specialist and the state civil defense services coordinator. The only reported injury was to a resident who suffered minor cuts from flying glass.
Area residents who fled in vehicles south on South Main St. to avoid the flaming plant close by the roadside were stopped a half-mile down the road by a chainlink fence that blocked the road when the new Interstate highway was constructed recently. Roland Duprey, a wrecker service operator with cutting torches cut out a roadway through the fence allowing state and local police to drive evacuees’ vehicles onto the Interstate so they could continue to homes of friends or to a temporary shelter established by town officials.
