North Carolina has issued the nation’s first National Pollutant Discharge Elimination System (NPDES) permit for the dewatering of power-plant coal-ash ponds in upland areas. The permit allows Duke Energy to begin the process of closing two ponds at its Riverbend Steam Generation Plant near Mount Holly, N.C.

Issued after more than a year of negotiations with the U.S. Environmental Protection Agency over protocols for handling wastewater seeping through nearby soil, the permit will serve as a model for addressing other Duke-owned sites across the state, including an idled power plant near the Virginia border, where a February 2014 discharge heightened awareness of the ponds’ environmental and public health hazards.

Tom Reeder, the state’s assistant secretary for the environment, says the Riverbend facility was chosen for the first permit because of its location upstream from the prime drinking-water supply for the city of Charlotte. “We wanted to be sure the state’s largest city was protected,” Reeder says.

The process calls for using the plant’s existing treatment system for decanting and treating water to within three feet of the coal ash. A package plant installed on site will bring the remaining interstitial water up to Clean Water Act standards for discharge through the normal outfall.

“The permit doesn’t specify a treatment process, but we’re confident that it can be done using off-the-shelf technology,” Reeder says, adding that the dewatering process should take about nine months. Then, the remaining wet ash will be excavated and transferred to lined landfills.

Dewatering of two ponds at the L.V. Sutton Steam Plant, near Wilmington, also has begun under a state-issued modification to the facility’s existing NPDES permit. By the end of this summer, Reeder hopes to have permits in place for the remaining high-priority sites. According to company financial data, Duke plans to spend $1.3 billion over the next four years on ash cleanup operations at the four North Carolina sites and at a fifth power plant in Belton, S.C.