State office building downtown closed in wake of latest manhole explosion

An Eversource truck on Wednesday was parked on Bowdoin Street on Beacon Hill, the location of a manhole explosion Tuesday night in which two Eversource workers were injured.David Ryan/Globe Staff

After a manhole explosion Tuesday injured two Eversource workers and forced the shutdown of a state office building, Mayor Michelle Wu said the city would seek accountability once an investigation into the incident is complete.

“We are working closely with the federal investigators,” Wu told reporters on Wednesday. “OSHA is leading the investigation.”

The explosion on Bowdoin Street Tuesday night was the latest in a string of incidents involving manhole fires and explosions in Boston in recent months. Another incident was reported Tuesday morning at Congress Street and Quaker Lane, where smoke was seen pouring out of a manhole.

The Edward McCormack state office building in downtown Boston, which includes the offices for Attorney General Maura Healey, was closed Wednesday in the wake of the incident on Bowdoin Street.

The explosion sent two Eversource workers to nearby Massachusetts General Hospital. One worker was treated for severe burns and the other was treated for possible smoke inhalation, said Jim Borghesani, a spokesperson for the Suffolk District Attorney’s office.

Several witnesses reported hearing the loud explosion from several streets away. Ravi Lala, 47, was exiting a nearby Target when he saw one of the workers emerge from the smoke, with his clothes “half burnt” and still smoldering. The injured worker urged him and other bystanders to help tear his clothes off. Lala said the man was “overheated,” suffering from “diffuse burns,” and in too much pain to stand still.

“All of this happened within maybe two minutes, before first responders arrived,” he said. “I have a healthy respect for first responders, putting their lives down on the line — especially after witnessing something like this firsthand.”

William Hinkle, a spokesman for Eversource, said the workers had been performing routine maintenance on a piece of underground equipment in a sidewalk vault when the explosion occurred.

“Our focus remains on supporting both of our employees and their families and we ask that their privacy is respected,” Hinkle said in an e-mail to the Globe Wednesday. “We also want to thank the local first responders from Boston for their quick response and action at the scene last night.”

Hinkle said manhole explosions are typically caused by underground cable failures, which can ignite underground gases. The cables are part of Eversource’s electric infrastructure and can fail due to corrosion, wear, or any number of reasons, he said.

Hinkle attributed the manhole incident on Congress Street and Quaker Lane on Tuesday morning to underground cable failures.

He said the manhole at that location was “equipped with a new energy release cover, which worked as designed.” There were no injuries or property damage, nor was there a power outage, he said.

The energy release covers have a latch that prevents manhole covers from flying off. Hinkle said they are a “relatively new technology” and Eversource has been installing them on a regular basis to enhance safety and prevent accidents. He said 8 percent of manholes in Boston have the new energy release covers, and the company hopes to increase that “as quickly as possible.”

Nathan Phillips, a Boston University physiological ecologist who studies land-climate interactions in human-dominated environments, said that manhole cover explosions are often a symptom of a greater problem: citywide methane leaks.

“There’s two ingredients needed to trigger a manhole explosion. One is a fuel and the other is a spark. Any electrical fault can be the spark. And then the fuel is, more often than not, leaking natural gas from old, rusted pipes,” Phillips said.

The leaks create the acute danger of manhole explosions, which can turn the hundred-plus pound manhole covers into projectiles that endanger nearby persons and property.

During an incident in April 2017, a district fire chief described seeing a cover “reach at least 50 feet in the air” near Government Center. A July 2016 underground fire in Brockton resulted in 15 to 20 manhole explosions that damaged three cars, including one that caught on fire after the manhole it was parked over exploded.

Perhaps more insidiously, Phillips said, the leaks exacerbate climate change. A study published in October 2021 that monitored natural gas emissions in the Boston area between 2012 and 2020 found that an average of 49,000 tons leaked into the air each year. That is equivalent to the greenhouse emissions of roughly 263,950 cars operating for a year, according to an EPA calculator.

Commissioner Paul Burke briefs the media on the manhole explosion on Bowdoin st. ⁦@EversourceMA⁩ shut down the power ,companies have monitored the air quality in the surrounding buildings and determined them to be clear.The cause of the incident is under investigation. pic.twitter.com/vBGyreoRkt

— Boston Fire Dept. (@BostonFire) July 12, 2022

On Wednesday, Wu said the recent manhole explosions are a manifestation of the woes of aging infrastructure in an old city.

To have “the infrastructure to support a growing population means that we need to be regularly putting the funding and maintenance and energy into that as we go,” and it should be a priority, she said.

Wu said city officials would also be meeting with labor unions to discuss the issue.

The incidents Tuesday are the latest in a string of manhole explosions and fires in recent months:

• On June 2, one woman was injured when two manholes exploded on Federal Street in the Financial District. Witnesses said it sounded like a bomb detonated, the Globe reported.
• On May 25, a manhole explosion in Cambridge at the intersection of Cambridge and Columbia streets caused widespread power outages, according to Boston 25.
• On May 17, a heavy metal manhole cover flew into the air and a second was split in two in Back Bay, the Boston Fire Department said. No injuries were reported during the incident, which took place on Boylston Street during the lunch hour, the Globe reported.
• On Feb. 3, flames shot out of a manhole in the North End due to an underground electrical fire, according to WHDH.

Material from earlier Globe coverage was used in this report.

We are assisting @bostonpolice with closing the South Station and Purchase Street ramps to Rt 93 South following two manhole explosions downtown. @BostonFire in command of response. At least one person transported to a hospital. We will update when info available. pic.twitter.com/tFWcZRJ3pn

— Mass State Police (@MassStatePolice) June 2, 2022