SPRINGFIELD, Ill. (AP) — The owner of an abandoned power plant has agreed to clean up toxic waste dumped into the flood plain of the Vermilion River, boosting efforts to protest Illinois’ lone national scenic river.

Under a deal brokered by the attorney general’s office, Texas-based Vistra on Monday agreed to drain pits of water-soaked coal ash along the Vermilion River Middle Fork , about 120 miles south of Chicago.

The energy company also will dig a trench to collect contaminated groundwater and monitor eroding riverbank after major storms. Illinois Power built a coal-fired power plant in 1955. Dynegy bought the plant in 2000, closing it in 2011.