Connecticut Attorney General William Tong has filed a lawsuit against United Illuminating, alleging that the company failed to clean up contamination at the former English Station power plant in New Haven.
Officials have stated that the company is required to take all necessary steps to clean the site regardless of cost.
That also includes penalties of up to $25,000 per day.
The mayor of New Haven said the plant was deactivated more than 30 years ago.
Officials said it's been 10 years since UI was told to remedy the site.