An estimated 50,000 to 82,000 tons of coal ash and up to 27 million gallons of water were released Sunday into the Dan River in northern North Carolina via a broken pipe underneath a waste containment pond, according to Duke Energy Corp.
A 48-inch stormwater pipe ruptured Sunday at the retired Dan River Steam Station in Eden, North Carolina, Duke Energy said. The ash pond above the pipe is around 27 acres large, and the dam containing the water is unharmed, the utility said, according to AP.
The broken pipe was not reported by Duke Energy or the North Carolina Department of Environment and Natural Resources until Monday - nearly 24 hours after the Sunday incident.
According to Duke Energy, a security guard first noticed an unusually low water level in the ash pond at around 14:00 EST on Sunday, leading to the discovery of the broken pipe. Duke Energy’s first public notice of the spill came just after 16:00 EST on Monday.
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The state Department of Environment and Natural Resources said in a statement that it has begun an investigation, in addition to helping with the cleanup and measurement of water quality along the Dan River.
A water quality-monitoring team is checking the river, though Duke Energy maintains that downstream water quality has not been affected.
Downstream from the rupture in Danville, Va., which draws its water from the river, officials said water quality has not worsened.
"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," said Barry Dunkley of Danville Utilities.
Coal ash is waste left after burning coal that contains arsenic, mercury, lead, and over a dozen other heavy metals, many of which are toxic. The exact amount of spilled water and coal ash is still undetermined, though Duke Energy claims it will divulge the figure as soon as it can.
Duke Energy has been sued for its over 14 coal ash dump sites in North Carolina by groups concerned about the potential effects of the toxic waste material stored near waterways. Some of the groups criticized Duke for the Sunday incident, especially since the utility waited a day before announcing the spill to the public and did not immediately release water quality tests from the river.
"State environmental officials failed to immediately notify the public about a major toxic spill in one of our precious waterways. Coal ash is extremely dangerous and the communities near the spill deserve information about their health and safety," Stephanie Schweickert of the North Carolina Conservation Network said in a statement.
The coal ash pond can hold around 155 million gallons of water. However, there was likely less water than that in the pond, as coal-fired units at Duke Energy’s Dan River power plant were retired in 2012, the Charlotte Observer reported.
If the preliminary estimate - which states that 50,000 to 80,000 tons of coal ash leaked from the pond - holds true, it would be the third-largest coal ash spill in US history, according to EcoWatch.