Thursday, June 13, 2024

Cambridge firefighters deal with a manhole explosion Wednesday in Harvard Square. (Photo: Cambridge Police Department via Twitter)

Traffic snarls in Harvard Square are decreasing but expected to last into Wednesday afternoon after three manhole explosions, a Cambridge police spokesperson said.

There have been no reported injuries.

The first explosion came at 8:34 a.m. near 27 Brattle St., a Bluestone Lane Café, drawing first responders, closing the square to car traffic and restricting access for pedestrians. “If at all possible, people should avoid traveling through Harvard Square until further notice,” police said in an email.

At around 9 a.m. “another manhole popped” nearby, said Cambridge Police Superintendent Fred Cabral by phone. “Every once in a while, you see those manholes pop and there are electrical fires.” A total of three manhole explosions took place within a short period, all along the Brattle Plaza sidewalk, Cambridge acting fire chief Thomas Cahill said Wednesday afternoon.

A manhole is covered Wednesday in Cambridge’s Harvard Square after an underground explosion. (Photo: Marc Levy)

“They do happen frequently, but usually not as severe as this,” Cahill said, estimating that Cambridge’s fire teams typically respond to 25 to 30 a year, with this year’s figures feeling roughly consistent with that amount. “A lot of these high-voltage wires are underground – and underground for a long, long time. So you can imagine the toll the weather, the salt and everything has on them.”

The explosions led to a carbon monoxide release that demanded the evacuation of 50 Church St., the Harvard-owned Atrium Office Building. Equipment was brought in to clear the air, Cabral said.

JFK St. reopened to traffic around noon, Cabral said, while Brattle and Church streets remained closed to traffic into the afternoon.

When manhole covers go, they can fly upward of 40 feet into the air, Cahill said, but it wasn’t clear to fire officials what happened with the three Wednesday in Harvard Square. “So much gas had accumulated that when it finally ignited, there was enough force that it blew the caps clear off,” Cahill said. Enough force had dissipated by the third manhole to make it less dramatic, fire officials believed. “It’s just that lesser smoking, which you can see right now,” Cahill said, gesturing at the taped-off sidewalk behind him.

It wasn’t known when Harvard Square traffic patterns would be returned to normal, Cahill said.