BUTTE, Mont. (AP) — U.S. environmental officials and the company responsible for the nation’s largest Superfund site have reached a proposed agreement to set what could be the final terms of the decades-long cleanup in Butte, officials said Thursday.

The settlement, known as a consent decree, would require Atlantic Richfield Co. to spend at least $150 million in cleanup activities. It sets out the work that would be needed to be completed on Butte Hill to take the city off the nation’s Superfund list of contaminated sites.

The work includes the removal of mining waste and sediment, and the treatment of contaminated storm water and groundwater, according to a statement from the U.S. Department of Justice.

Butte was declared a federal Superfund site in 1983 because of the damage done by more than a century of mining and smelting.

The proposed agreement must be filed with the court and go through a public comment period before it takes effect.

Atlantic Richfield has spent $1.6 billion since 1989 in Butte and the Clark Fork valley, company vice president Patricia Gallery said at a news conference announcing the consent decree.

Environmental Protection Agency regional administrator Greg Sopkin said at the news conference that it is “a great day for EPA and a great day for Butte,” according to The Montana Standard.

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