The Sierra Club and the Conservation Law Foundation said they’ll file suit under the Clean Water Act in January if things don’t change at the power plant.
It was owned by Eversource until earlier this year, when it sold to Connecticut-based Granite Shore Power.
The plant discharges hot water into the Merrimack River. It’s considered a type of pollution, and the nonprofits have long said it harms the ecosystem. The plant’s federal discharge permit is also long overdue for an update. Its owners have said upgrades to cool the discharged water would cost millions.
An Eversource spokesman said though they no longer operate the plant, they deny the allegations. Granite Shore Power did not immediately respond to a request for comment.
