HARRIMAN - The amount of coal-ash sludge released Monday when an earthen dike failed at a Kingston Fossil Plant retention pond was triple what TVA has estimated.
A TVA aerial survey done Tuesday and made public Thursday shows that 5.4 million cubic yards of fly ash spilled, covering hundreds of acres, destroying three homes, damaging others and clogging the Emory River.
The agency previously had said an estimated 1.7 million cubic yards had burst through the coal-ash storage facility in Roane County about 1 a.m. Monday. TVA officials had said the pond contained about 2.6 million cubic yards of sludge and that two-thirds of it had spilled.
TVA surveyed the area Tuesday with a radar system using laser light and revised its estimates.
The agency estimates that 78,000 cubic yards of ash are on railroad tracks and Swan Pond Road. About 3,000 feet of Swan Pond Road and 1,500 Swan Pond Circle are affected by the slide, according to TVA.
Swan Pond Road remains closed, except for residents who live in the area.
Crews using bulldozers, backhoes and dump trucks have cleared about 350 feet of debris from the road and railroad tracks.
There is no estimate when the cleanup will be completed.
Water sampled downstream of the plant, including at Kingston Water District intake, shows that concentrations of sampled contaminants were below levels established by the Tennessee Department of Environment and Conservation to protect fish and aquatic life, according to TVA.
The water, with normal treatment plant filtration, also would meeting drinking water standards, TVA said. Water sampling and analysis by TVA and other agencies will continue to monitor for contaminants in the river.
The pond that breached covers about 40 acres and is one of three containment areas at the Kingston plant. The ash is a by-product of burning coal at the power plant, which sits near the Emory and Clinch rivers and is one of TVA's largest fossil plants. The Emory and Clinch flow into the Tennessee River,
It generates 10 billion kilowatt hours of electricity a year, enough to supply 670,000 homes, according to TVA. Construction on the plant was begun in 1951 and completed in 1955.
Environmentalists have criticized TVA, saying the slide was avoidable.
Hundreds of fish were floating dead downstream from the plant Tuesday, and state and federal agencies have yet to complete water quality testing.
TVA spokesman Gil Francis has said the fish may have died from the freezing cold that contributed to the breach, not pollutants.
Environmental Protection Agency spokeswoman Laura Niles said some toxic metals could be in the muck, including mercury and arsenic.
The bulk of the fly ash "consists of inert material not harmful to the environment," the TVA statement said.
TVA President and Chief Executive Officer Tom Kilgore said TVA may consider using a dry ash treatment process at Kingston that would reduce the chances of a similar event. Five of TVA's coal-fired plants use a dry ash treatment now; the other six, including Kingston, use a wet process.
TVA officials said 6 inches of rain over 10 days and overnight temperatures in the teens contributed to the dike's breach.
Reduced demand for electricity because of mild weather has led to the shutdown of nine units at Kingston and 15 other TVA fossil units, according to TVA.
More details as they develop online and in Saturday's News Sentinel.
The Associated Press contributed to this report.