Duke Energy Corp. said on Monday that a coal ash pond at its former power plant in Eden, N.C., dumped 50,000 to 82,000 tons of coal ash and up to 27 million gallons of water into North Carolina's Dan River.
The Charlotte Observer reported that the spill was ongoing as of Tuesday when it reported the incident.
Duke Energy's coal-powered Dan River Steam Station in northern North Carolina was retired in 2012. It is about 130 miles northeast of Charlotte, N.C.
The coal ash spill came after a 48-inch stormwater pipe located beneath a coal ash pond broke on Sunday afternoon.
The 27-acre coal ash pond, with a liquid capacity of 155 million gallons, drained waste into the Dan River through the broken pipe.
The waste, according to The Associated Press, contains "arsenic, mercury, lead and over a dozen other heavy metals, many of them toxic."
In a statement released at about 9 a.m. Monday, Duke Energy spokeswoman Erin Culbert said it was a security guard who first noticed at about 2 p.m. on Sunday that the ash pond had an unusually low water level.
He alerted management and an investigation found that a broken pipe had spilled up to 82,000 tons of coal ash and water into the Dan River.
Culbert said, "We’ve had some temporary solutions that have intermittently worked at times during the day, but we are still working on a short-term solution and the long-term repair."
Reports said the ash could be seen on the banks of the river on Monday and that the water had a gray tint due to the ash contamination.
Duke said it alerted local emergency agencies and the N.C. Department of Environment and Natural Resources.
The North Carolina environmental agency reported late Monday afternoon that it has alerted districts whose downstream water intakes are close to the spill.
According to the Charlotte Observer, Danville, Va., has its drinking water intake about 6 miles downstream of the pond.
Despite the massive amount of waste containing highly toxic metals spilled, Danville officials said they have not detected any contamination of their water source and do not believe the city's water supply has been affected.
Barry Dunkley, director of water treatment for Danville, said, "All water leaving our treatment facility has met public health standards. We do not anticipate any problems going forward in treating the water we draw from the Dan River."
The assertion was made despite the fact that results of water quality tests were not available as of Tuesday.
However, the North Carolina environmental agency admitted Monday that "it is early in the investigation and state officials do not yet know of any possible impacts to water quality."
Environmental groups have criticized Duke for waiting until Monday afternoon to alert the public about an incident first detected on Sunday afternoon.
The spill was detected at about 2 p.m. Sunday but Duke's first public notice was issued at 4:03 p.m. Monday.
Duke’s handling of ash near waterways has been under scrutiny for some time. Last year, the N.C. Department of Environment and Natural Resources sued the company over the matter.
Environmental groups also filed suits against Duke to remove the ash at its dumpsites.
Duke reportedly maintains 14 coal ash dump sites close to major water supplies.
The environmental risk of coal ash dumps was brought to focus after a spill of 1 billion gallons of ash slurry at a Tennessee Valley Authority power plant in 2008.
Meanwhile, the EPA has announced that it would release its first ash-handling rules by December.