PITTSFIELD — The operator of Pittsfield's last peaker plant has been fined $21,500 for exceeding state emission limits three times last year.

The state Department of Environmental Protection said that the Pittsfield Generating Co. plant at 235 Merrill Road "reported deviations of its hourly nitrogen oxide emission limit, which occurred twice in July 2025, and a deviation of its hourly ammonia emission limit, which occurred once in December 2025."

Under a state permit in effect through Oct. 28, 2027, nitrogen oxide emissions for the plant are capped at 16.2 pounds per hour when burning natural gas and 22.8 pounds per hour when burning oil, and ammonia emissions at 14.0 and 20.0 pounds per hour for the same respective fuels.

The permit limits are designed to restrict how much pollution industrial facilities release into the atmosphere at any given time.

“Rigorous compliance with state air regulations requires constant and careful diligence,” said Michael Gorski, director of MassDEP’s Western Regional Office in Springfield. “Significant penalties are imposed to hold parties accountable and deter future noncompliance.”

The state DEP said the company agreed to pay the penalty and conduct training aimed at preventing future violations.

“Safey and environmental compliance are our highest priorities," a spokesperson from plant owner Hull Street Energy told The Eagle. "We have resolved this matter fully with the MassDEP and are enhancing staff training to ensure the Pittsfield facility remains a reliable, responsible energy provider for the community.”

Peaker plants are backup power stations that switch on only when electricity demand spikes. They act as a safety valve for the grid — kicking in during heat waves, cold snaps or other moments when overall usage surges. The state DEP estimates that peaker plants operate less than 10 to 15 percent of the time.

The Pittsfield fossil-fuel-powered plant is the last of its kind in the Berkshires. Two others, located on Woodland Road in Lee and Doreen Street in Pittsfield, closed in 2022 and have since been dismantled.

In December, the Pittsfield City Council backed a plan that would convert the facility into a battery storage facility amid ongoing concerns about the plant’s pollution and its impact on nearby neighborhoods. The plant is the city's largest greenhouse gas emitter and is less than 950 feet from Allendale Elementary School. The city and the Berkshire Environmental Action Team aim to partner with Hull to execute the conversion, though it's unclear if Hull is receptive to the plan.