The North Carolina Dept. of Environmental Quality has proposed classifications for 32 coal-ash impoundments at 14 powerplant sites owned by Duke Energy. The draft classifications, released on Dec. 31, prioritize the cleanup of residual ash impoundments near coal-fired plants based on the impoundments’ integrity and potential risks to groundwater and surface water.

The proposed classifications are the latest step in the implementation of a state law that was enacted following a February 2014 discharge from an ash pond at an idled powerplant, near Eden, N.C., that fouled 70 miles of the Dan River.

The classification designates eight impoundments at four sites as being high risk, requiring full excavation and disposal by December 2019. Another 12 ponds deemed as intermediate-level risks must be excavated and closed by the end of 2024. Four impoundments considered low risk are to be closed by December 2029, with draining and liner caps as potential options.

Eight ponds are awaiting classification, pending receipt of groundwater contamination risk data; however, they likely will fall into the intermediate- or low-risk categories, NCEDQ says.

According to a statement from Duke Energy, ash excavation is underway at six locations, including the four high-risk plants, where on-site landfills will be constructed. Duke also has submitted comprehensive groundwater assessments to NCDEQ for each of the 14 coal plant sites.

While Duke declined to give a cash investment figure for the work performed to date, the company’s financial statements show a projected $4.5-billion asset retirement obligation for closure of the North Carolina sites, as well as coal-ash impoundments in South Carolina, Indiana and Kentucky.

Final classifications are expected to be released in early summer 2016.