Duke Energy is set to spend $3.4 billion to clean up 32 coal ash storage ponds located across North Carolina to comply with the state’s recently enacted regulations aimed at preventing a repeat of the February 2014 spill that contaminated portions of the Dan River.

Whether that amount is sufficient to cover the full scope of the Charlotte, N.C.-based utility’s cleanup obligation at its operating and closed coal-fired power plants remains to be seen, however.

Duke Energy has already announced plans to excavate and rebury ash in lined landfills at four sites classified as “high-risk” by North Carolina’s Department of Environment and Natural Resources (DENR).

Work at an additional 10 sites has yet to be determined, but Duke Energy has stated that these and other locations could be fully addressed using less expensive approaches such as reusing the ash as construction fill or concrete admixture, or installing waterproof caps on existing disposal ponds to prevent leaks.

Should DENR require full excavation and landfilling at every site, Duke Energy claims the cost would be as much as $10 billion.

The remediation plan is already off to a difficult start, with the North Carolina Division of Water Resources rejecting Duke Energy’s initial proposal for assessing groundwater conditions at the 14 sites, citing a lack of detail in its data collection models. Revised plans are to be submitted by early December.

Duke Energy and DENR already face scrutiny for their handling of the February spill that sent 39,000 tons of ash into the Dan River.  The U.S. Attorney’s office launched an investigation into allegations of improper relationships between Duke Energy and state environmental officials, and empanelled a grand jury to hear evidence. No charges have been brought.