The North Carolina Department of Environmental Quality (DEQ) has released a more detailed description of how it determined a low-to-intermediate risk assessment of the Belews Creek Steam Station ash impoundment.
The DEQ released its initial low-to-intermediate risk ranking of the site on Dec. 31, 2015, with a guarantee that more detailed information would be released within 30 days.
According to the information released Friday, the DEQ is still waiting on a variety of information from Duke Energy, but the report noted that the classification for groundwater risk would be noted as low if either no receptors (wells) were impacted by the impoundment, or if alternative water is made available to all residents whose wells are being being impacted.
Currently Duke Energy is supplying bottled water to a number of residents around the ash impoundment, although the company says they are not the source of contaminants that have been identified in those wells.
According to the detailed report, DEQ is still dealing with six data gaps that need to be filled in order to complete a full analysis of the impact the impoundment may have on groundwater in the area.
Those gaps include:
— Incomplete capture zone modeling in fractured bedrock for upgradient and side-gradient supply wells in the immediate vicinity of the impoundments
— Incomplete geochemical modeling
— Incomplete background concentration determination
— Horizontal and vertical extent of contamination downgradient not well defined
— Potential contamination resulting from the on-site landfill and structural fill not addressed
— Groundwater flow in bedrock not well defined
The report notes that, according to data provided by Duke Energy in an independent Comprehensive Site Assessment (CSA), there are no reported supply wells within 1,500 feet downgradient of the impoundment boundary.
The CSA, conducted by HDR Engineering, Inc. of the Carolinas, showed the facility did have some seepage into groundwater noting that some elements, including antimony, iron, manganese, pH, and vanadium, were likely naturally occurring while other elements found in groundwater at the site, including arsenic, beryllium, boron, cadium, chloride, cobalt, thallium, and TDS, “appear to be caused by the source.”
The 2015 CSA found no imminent hazards to public health and safety, but noted that corrective action at the site was required to address soil and groundwater contamination.
The DEQ report released Friday, also notes that surface water contamination is not a key factor in the low-to-intermediate risk classification because the impoundment is not located within the 100-year floodplain.
The dam at the facility, as it is exists now, is ranked as a high risk, but the report notes that planned repairs and the dewatering of the impoundment will reduce that to a low risk ranking.
The required minimum repairs to the dam include tree removal, slope improvements, grouting pipes and installing a weighted filter overlay.
Duke Energy began work on those repairs in July and expect to complete them by the fall.
“We are going in and adding several layers of sand and stone and then an additional layer of top soil that will be vegetated,” said Duke Energy spokesperson Zenica Chatman. “It will add another layer to strengthen the dam. It is all about improving our system. The overlay will serve a dual purpose. It add an additional layer of stability and strength, but it will also address seepage by redirecting those seeps back into the pond.”
She noted that the work was a result of increased attention to ash ponds following the Dan River spill, adding that the company was inspecting and upgrading facilities throughout its system as well as increasing groundwater monitoring efforts.
“The ash basin at Belews Creek is operating safely, but we are always working to improve operations across our system,” she said. “We have between 30 and 35 identified seeps at this site. The total seepage volume at most sites is very small compared with the wastewater being discharged daily through normal outfall. For example Belews’s average daily discharge is 8.1 mgd with seepage at 0.2296 mgd (2.83%). Seeps generally occur at low flows and contain low levels of constituents.
“Dewatering and permanently closing ash basins will ultimately resolve the seeps,” she said.
A public hearing on the state’s risk rating for the Belews Creek ash impoundments will be held Thursday, March 24, at 6 p.m. at the Walnut Cove Public Library.
“The public meetings are a great opportunity for the public to get involved in the classification process,” said Department of Environmental Equality (DEQ) Assistant Secretary Tom Reeder. “DEQ is committed to relying on science and public comment to determine closure deadlines. We welcome feedback from the communities impacted by Duke Energy’s coal ash ponds and hope that the public participation process produces additional scientific and technical data that can help inform our final determinations.”
Nicholas Elmes may be reached at 336-591-8191 or on Twitter @NicholasElmes.