PEORIA, Ill. (AP) — A federal judge has ruled a coal fired energy plant outside Peoria has allowed too much soot to be emitted from its smoke stacks.

U.S. District Judge Joe B. McDade wrote in a Tuesday order that Illinois Power Resources Generating LLC must work to clean emissions from the E.D. Edwards power plant.

The Sierra Club and other groups filed the lawsuit in 2013. They alleged the plant then owned by Ameren Illinois violated the Clean Air Act. IPRG acquired the plant after the lawsuit was filed.

IPRG is a subsidiary of Houston-based Dynegy. Dynegy spokesman Micah Hirschfield said the company was “disappointed with the judge’s decision.”

Joyce Blumenshine of the Sierra Club Heart of Illinois says the court has done good by holding Dynegy accountable for the harm it’s done.