January 6, 2020
On December 31, 2019, Duke Energy (Duke) and the State of North Carolina, along with several community groups, reached a settlement over the closure of nine of Duke's largest coal ash basins at six separate facilities throughout the state. Short of full excavation, Duke agreed to excavate approximately 80 million tons of coal ash and relocate it to lined landfills onsite, amounting to the largest coal ash cleanup in the nation's history. "This agreement significantly reduces the cost to close our coal ash basins in the Carolinas for our customers, while delivering the same environmental benefits as full excavation," said Stephen De May, Duke Energy's North Carolina president, in a statement on the company's website.
The December 31, 2019, settlement followed an April 1, 2019, order by the North Carolina Department of Environmental Quality under the Coal Ash Management Act (CAMA) to excavate the basins. Duke had contested the order in the North Carolina Office of Administrative Hearings (OAH) shortly after the April 1, 2019, decision. At issue was evaluation of the different closure options.
How Exponent Can Help
Exponent scientists have provided consulting advice and expert opinions on coal ash basin closure options. We addressed several technical aspects such as:
- Analyses of compound (e.g., boron) leaching rates from coal ash to groundwater under different basin closure scenarios (e.g., cap in place, excavation).
- Evaluation of contaminant fate and transport models (USGS numerical codes called MODFLOW and MT3DMS) to predict the spatial extent of ash-related compounds in groundwater inside and outside ash basin regulatory compliance boundaries.
- Analysis of seep discharge rates under basin decanting scenarios.
- Air emissions associated with basin closure scenarios.
- Net environmental benefit analysis (NEBA) for different closure options.