As part of a signed agreement with the U.S Fish and Wildlife Service, North Carolina Department of Environment and Natural Resources and Virginia Department of Environmental Quality, Duke Energy has agreed to foot the bill for any costs related to the recent Dan River coal ash spill.

In February, a Duke Energy plant near Eden, North Carolina, spilled roughly 140,000 tons of toxic coal ash and wastewater into the Dan River, which flows into both North Carolina and Virginia. The spill was enough to coat some 70 miles of the river in dark toxic sludge.

In signing the understanding with the state agencies, Duke agreed to pay any "reasonable" cost associated the spill. The agreement is similar to the one it signed early this year with the Environmental Protection Agency.

"This agreement represents a significant milestone in Duke Energy's ongoing efforts to restore and monitor the Dan River and surrounding environment," the company said in press release Monday. "Duke Energy is fully committed to the river's long-term health and well-being. River water quality has returned to normal and drinking water has remained safe."

Duke Energy has already spent some $15 million in containing the spill and mitigating its immediate ill effects. Though the energy company claims things are back to normal, conservationists are likely to pressure the conglomerate into additional cleanup efforts should further contamination come to light.

Both the state agencies and the company hope the agreement can help avoid lawsuits as officials continue to monitor toxicity levels and evidence of pollution in the Dan River.