Hoping to avoid another controversial environmental clean-up, the  North Carolina legislature has enacted new rules for managing power plant coal ash residue stored in open-air pits and lagoons across the state.

In addition to banning the construction or expansion of coal ash impoundment facilities as of October 1, 2014, the legislation requires the state Department of Environment and Natural Resources (DENR) to classify more than 30 coal ash impoundment sites owned by Charlotte-based Duke Energy as high-, intermediate-, or low-risk by the end of 2015.

High-risk sites must be excavated and placed in a lined landfill by the end of 2019, while all intermediate sites to be similarly remediated by 2024. Low-risk sites can be capped to prevent ash from entering streams and other water supply sources.

In addition, Duke Energy, the nation's largest electric power holding company and owner of a site involved in a February 2014 spill at a retired power plant that sent as much as 39,000 tons of coal ash into the Dan River, must convert its power facilities to “dry” fly ash, rather than liquids or sludge by 2018. The utility is also required to test private wells, and eventually replace contaminated drinking-water supplies for residents.

In a statement, Duke Energy President and CEO Lynn Good said the legislature’s comprehensive action” gives the utility “direction to move forward with a stronger standard for the management of coal ash at our facilities. We will immediately begin adapting our strategy to meet the requirements in the 2014 Coal Ash Management Act.”

Both Duke Energy and DENR have come under fire for their handling of the February spill and ensuing clean-up, which the utility says was completed in mid-July with the last 2,500 tons of ash and sediment removed from just upstream of the Schoolfield Dam in Danville, Va.

In late February, the U.S. Attorney’s office launched an investigation into allegations of improper relationships between Duke Energy and state environmental officials that may have compromised regulatory enforcement. A federal grand jury began hearing evidence in May.

In early August, it was revealed that Governor Pat McCrory (R), who worked for Duke Energy for nearly 30 years, failed to disclosed ownership of the utility’s stock in 2013 to North Carolina’s Ethics Commisision. Claiming the omission was unintentional, McCrory amended his filing to state that he owned more than $10,000 of Duke Energy stock as of December 31, 2013.

McCrory sold his Duke Energy holdings two months after the Dan River spill