Ameren Missouri has told state regulators it will shut down the 61-year-old Meramec coal-fired plant in Oakville by 2022, or possibly sooner pending stricter rules on greenhouse gas emissions.

Environmental groups that want Ameren to reduce its reliance on coal are hailing the decision.

The Sierra Club sued Ameren Corp. in federal court earlier this year seeking to compel the company to reduce air pollution at the Meramec facility and two other area power plants. The lawsuit also asks a court to levy financial penalties for past violations.

Ameren’s board of directors approved the Meramec closure in late June.