A state appeals court will hear whether it should allow a five-year-old lawsuit trying to force Duke Energy Corp. to clean up groundwater contaminated by its North Carolina coal ash pits.

The Charlotte-based electricity utility argues to the Court of Appeals on Thursday that the lawsuit should be dismissed.

Duke Energy lawyers say the company is following deadlines set by a state law requiring excavation or other closure of the pits. Conservation groups pushing the case say Duke Energy is doing little on its own to clean up groundwater pollution that’s lasted for decades.

One of the country’s largest electricity companies last month agreed to pay an $84,000 penalty and stop potentially toxic waste at three coal-burning power plants from leaking into groundwater and nearby rivers.