Transformer explodes, catches fire in downtown Lexington Monday evening; no injuries reported

Last updated Friday, Aug. 12 at 6:34 p.m. with additional comments from Eversource, including new information about the level of PCBs present in the spilled cooling oil

Just before 6 p.m. Monday evening, a large transformer exploded and erupted in flames at an Eversource substation near the post office between Lexington Center and the Minuteman Bikeway.

Despite the dramatic appearance and scale of the three-alarm fire, no bystanders or firefighters were hurt, Lexington Fire Chief Derek Sencabaugh said. 

But plenty of community members were downtown when the explosion occurred.

Alexandra Schweitzer was driving toward the post office yesterday evening; when she was across from CVS, “I saw a lot of smoke and then a big poof of bright orange flame,” she said. “It was kind of bizarre, to be honest…it didn’t even look real.” 

Schweitzer continued driving, planning to park across from the post office, but when she looked back, “there was another poof – bang, really – more smoke…and probably three or four of those big fireballs.”

“I just sort of kept going – I decided maybe being right in front of a building on fire wasn’t the smartest thing to do,” she said. Fortunately, “the fire trucks were there [it] seemed like immediately.” More trucks arrived, as well as some ambulances, at least in part as a precaution in case any firefighters suffered heat exhaustion under their heavy gear.

“In a funny way, it was very surreal, because it was quiet,” Schweitzer said. “No one was running around screaming – the sirens came, but then they stopped.”

Chonnipa Jomkhamsing was working in the kitchen at Love at First Bite, across the street, when her coworkers informed her of the fire. When she came outside to look, fire and smoke were “all over the sky,” she said.

It took about an hour to put out the original fire, Sencabaugh said – but the firefighters had to keep dousing cooling oil that had spilled from the transformers for a couple more hours to keep the fire extinguished. They remained in the area until around midnight last night. Some roads in the Center and the Minuteman Bikeway were closed off following the fire, but most had reopened by Tuesday morning.

Sencabaugh was still supervising the scene Tuesday morning, where at least three separate transformers belonging to Eversource were damaged by the fire, he said. The large transformer, which caused the fire, was left completely blackened; another transformer under a small tree had become so hot that it “melted the internal components” of a third transformer which feeds downtown Lexington. 

“Even though it was heavily damaged and melted, it still ran,” Sencabaugh said. That’s why there was no major power interruption to downtown businesses. Eversource did not switch power to the green generator currently visible above ground near the Minute Man Statue until after midnight, once all the businesses had closed.

To work on repairs and assess the damage, “it was necessary to switch approximately 50 customers in the area to generator power overnight,” Eversource spokesperson Chris McKinnon confirmed in an email to LexObserver. “Once we complete those repairs, all customers will be switched back.” He added that Eversource “[does] not anticipate any power issues in the area” except for a possible planned outage when customers are switched back to the system from the generator.

As of Tuesday evening, Eversource still had not confirmed the exact cause of the fire. “We are actively investigating the exact cause of yesterday’s transformer fire at our substation in Lexington,” McKinnon wrote. At least half a dozen Eversource trucks were parked downtown Tuesday to work on repairs. 

Though the cause has not yet been confirmed, Sencabaugh suspected that high demand on the electric system in the hot weather was to blame. But on Tuesday evening, McKinnon wrote that “we do know the transformer was not overloaded at the time.”

Such an explosion is not unprecedented. A transformer in the same area of Lexington Center exploded in July about 20 years ago, according to Sencabaugh: “We did this once before.”

As of Friday evening, McKinnon had not responded to a question about the age and life expectancy of the transformer that exploded.

Regionally, there have been more fires than usual this summer, Sencabaugh said. Less than two weeks ago, Lexington firefighters pitched in alongside firefighters from 17 other towns to put out a six-alarm fire in Concord. 

“The intensity has been up, and the response has had to be up,” Sencabaugh said. He also noted that it’s important to rotate crews out for firefighter safety during such hot weather; “when I got here [last night], everybody’s face was cherry red,” he recalled. Daytime temperatures above the 80s for the better part of a month have caused fire departments across the region generally to “requir[e] a lot more assistance from other communities.” 

Eversource has not seen more transformer fires than usual this summer in Eastern Massachusetts as a consequence of the heat, according to McKinnon.

The makeup of the cooling oil spilled from the transformers was not initially known, so it was tested at a lab as a precaution. Clean Harbors is disposing of all waste liquid. “A lot of transformers are now filled with vegetable oil and things like that…so they’re a lot more environmentally safe,” Sencabaugh said.

On Tuesday evening, McKinnon wrote that the transformer oil contains 106 parts per million of polychlorinated biphenyls (PCBs). PCBs “have been demonstrated to cause a variety of adverse health effects,” according to the United States Environmental Protection Agency (EPA).

“Based on the cleanup completed so far and the exclusion zones created, we are not aware of any current risks to the community,” McKinnon wrote. “We have made the Massachusetts Department of Environmental Protection aware of the situation as well as the steps we have implemented, and as we continue to perform cleanup work we will collect additional samples as necessary.”

The Toxic Substances Control Act (TSCA) strictly regulates the disposal of “used oil containing PCBs at concentrations of 50 parts per million (ppm) or greater,” according to the EPA.

As of Friday evening, McKinnon had not responded to a question from LexObserver about what Eversource considers a safe and typical ppm level of PCBs for cooling oil.