Duke Energy has signed an agreement with the US Environmental Protection Agency to have it oversee the cleanup of toxic coal ash that spilled into a North Carolina river earlier this year. For days this February, tens of thousands of tons of coal ash flooded into the Dan River, which flows between North Carolina and Virginia, from a reservoir beside an old Duke power plant. Duke has been cleaning it up in the time since, with the EPA monitoring its progress, and it's now agreed to compensate the EPA for all past and ongoing oversight costs.

"Protection of public health and safety remains a primary concern.""EPA will work with Duke Energy to ensure that cleanup at the site, and affected areas, is comprehensive based on sound scientific and ecological principles, complies with all federal and state environmental standards, and moves as quickly as possible," Heather McTeer Toney, an EPA regional administrator, says in a statement. "Protection of public health and safety remains a primary concern, along with the long-term ecological health of the Dan River."

With the EPA, Duke will be working to locate and remove all coal ash deposits remaining in the river. It's already been working toward that goal, though the EPA's latest report doesn't say how much progress it's made toward fully cleaning up the ash, which contains hazardous substances including arsenic, lead, and mercury. The EPA has, however, not yet see signs that the river has been exceeded levels of these substances that could make it harmful to human health. It intends to continue sampling to ensure that the river remains safe for recreational use.