Photo: A Belmont Light equipment truck stationed at the Hittinger substation during the outage.

Worcester Street’s Hannah Liberty decided Monday morning that getting on a crowded MBTA bus with a mob of sweaty, miserable commuters on the hottest day of the year was not something she was going to do this Monday morning.

Liberty called her job and told them she would work from home which would include taking a three-hour business call from Seattle, all inside her air conditioned house.

“I thought that was a good idea,” she said.

By 1:30 p.m., Liberty was sitting on the second floor of the Belmont Public Library, laptop and phone in hand, as she prepared for the West Coast call.

“About an hour ago, my lights suddenly went out so no air conditioning and no internet,” said an aspirated Liberty, as she sat next to a pair of chatty high schoolers, not the optimum location to take an important call.

“It turned out to be a mistake not to head off to work,” she said. 

Liberty and thousands of other residents found themselves scrambling for a cool place and a connection to the web when around 12:30 p.m., Monday, June 12, a transformer failure at the Hittinger Street substation created a major power outage in large sections of Belmont.

According to Belmont Light spokesperson Aidan Leary, intense heat – the high in Belmont hit 94 degrees – a spike in demand, as well as aging infrastructure were all contributing factors to the equipment failure.

Approximately 2,000 of Belmont Light’s 11,250 customers were without electric service when the outage started, including Belmont High School, Chenery Middle School, and the Winn Brook Elementary School.

Belmont High students were released for the remainder of the day after it since power would not be restored until late afternoon.

When the severity of the outage was known, Belmont Light’s operations team activated its contingency plan, which included implementing a temporary generation protocol to restore power and ensure that the electrical delivery system would be able to handle all demand going forward, said Leary. 

A Belmont Light equipment truck was stationed at the Hittinger substation, where it was joined by four white SUVs from American Electrical Testing Co. of Foxboro. The firm is known for its array of transformer services.  

Belmont Light restored power to about half of the impacted customers within two hours. By 7 p.m., power had been restored to another 500 customers. The remaining 500 customers in the southeast corner of Belmont along the border with Cambridge were back online by 10 p.m. 

Several residents asked the Belmontonian why the Hittinger substation is in use since the new Blair Pond substation – built to replace the three smaller transmission and distribution structures at Hittinger Street, at the former Light Department Headquarters on Concord Avenue and adjacent to the Chenery Middle School – was commissioned in May. 

Leary said while the new substation located on Flanders Road off Brighton Street is energized, the Master Plan created by Belmont Light to meet future demand calls for the electrical load to be routed through the three older facilities until they are decommissioned in a couple of years.

In addition to the major blackout, there were intermittent outages throughout Belmont as the hot weather caused demand to spike and the system was stretched to its capacity.

Belmont Light will continue to investigate the cause of Monday’s outage and inspect equipment, said Leary.