Duke Energy discovered a coal ash spill Feb. 2 after a 122-cm (48-in) stormwater pipe ruptured beneath a coal ash pond near Eden, North Carolina. The ash ponds are storage lagoons containing a mixture of water and ash, a waste product from coal-burning power plants. The coal ash contains hazardous heavy metals including arsenic, lead, and mercury. The spill sent between 90,850 and 102,206 m3 (24 million and 27 million gal) of wastewater and as much as 35,380 metric tons (39,000 tons) of coal combustion residuals into the Dan River over seven days. Residuals traveled as far as 113 km (70 mi) downstream.
The North Carolina Department of Environment and Natural Resources (DENR) has been testing water quality at locations upstream and downstream of Duke Energy’s Dan River facility since the agency was notified of the spill on Feb. 3. See the results here.
In total, DENR’s state laboratory has been analyzing water samples from the Dan River for sulfates, nutrients (nitrogen and phosphorus), total suspended solids, and 28 metals. Following the spill, in mid-February, tests showed falling levels of arsenic and copper, both below surface water standards. However, aluminum and iron levels remained higher than the standards into late February, as reported by DENR on March 7.
“What we’re seeing is that once the discharge is diluted by the river water, it’s within state surface water standards,” said Tom Reeder, director of the North Carolina Division of Water Resources. “Federal discharge permits include dilution as a factor in determining acceptable discharge levels.”
One of DENR’s concerns is the deposition of coal ash on the river bottom and its long-term effect on the aquatic environment.
The ash ponds, installed in decades past, were afforded minimal regulatory oversight until a December 2008 dike rupture in Tennessee that released more than 3.8 million m3 (1 billion gallons) of slurry with a cleanup cost of $1 billion. The disaster led to increased awareness and groundwater testing requirements in 2009. It also ended an exemption from North Carolina’s dam safety laws.
The Feb. 2 spill may result in further regulatory oversight of coal ash storage. The incident has led to a statewide inspection of coal-fired power plants and the formation of a coal ash pond task force, which is separate from ongoing enforcement action review. Part of the investigation has included a lengthy review of the permit status of Duke Energy’s 14 North Carolina facilities.
DENR issued violation notices to six Duke Energy power plants, including the Dan River plant, for failure to obtain federally mandated National Pollution Discharge Elimination System (NPDES) stormwater permits. By state law, an NPDES permit is required to discharge stormwater from steam electric power generating facilities to state waters. Regulators did indicate that they were aware, since 2010, that some facilities lacked the required permits.
DENR’s actions represent the first time in state history an administration has filed a lawsuit to address unpermitted discharges from coal ash ponds. The ponds exist at a total of 14 coal-fired power plants across North Carolina. At the federal level, the EPA has announced that it will issue a rule concerning coal ash regulations by December. Read more.
Duke Energy is reviewing the feasibility of shutting down the lagoons. Other options for disposing of coal ash include using it in cement and putting it into dry storage in lined landfills. According to a Duke spokeswoman Erin Culbert, as reported in the Charlotte Observer, of the 96 million metric tons (106 million tons) of ash Duke stores, nearly 80% is kept in lagoons.