The Tennessee Valley Authority's 11 coal-fired power plants produce almost 6 million tons a year of coal waste, and most of it has been stored in waste ponds or landfills, according to TVA data.
At the Kingston Fossil Plant, where on Dec. 22 a landfill's earthen wall collapsed, spilling 1.2 billion gallons of wet coal sludge into the Emory River and nearby residential farmland, waste generated in 2005 alone totaled 408,000 tons, according to TVA data given to the U.S. Department of Energy.
But Kingston isn't the largest coal-waste producer among TVA's coal plants. It came in fourth. TVA's plant near Nashville produced 1.6 million tons of waste in 2005, records show, while a Kentucky plant had more than 1 million tons and a plant in Alabama had just under 1 million tons.
TVA officials say the coal ash is safe and the utility's waste totals amount to less than 5 percent of the nation's 126.3 million tons of coal waste. But the Kingston spill has spurred environmental groups nationwide to call for new regulation and tougher cleanup protocols on anything coal related.
Patrice Simms, an environmental attorney with the Natural Resources Defense Council, looked at the DOE data earlier this year to rank the top 100 waste producers. He used the information to urge federal and state authorities to examine how coal waste is and should be handled.
"When we talk about the tons of coal waste produced every year, that's just one year. That's not what's in landfills," he said. "As far as we know, there is no obligation to report how much accumulated waste is in ponds and landfills."
TVA spokeswoman Barbara Martocci said the agency is being "transparent."
"We do have an open manner," she said.
In Tennessee, the spill has prompted the Tennessee Department of Environment and Conservation to examine the landfills and what dangers, if any, they may pose.
Cumberland Fossil Plant, northwest of Nashville, produced 1.6 million tons of coal waste in 2005, the last year the DOE required the report. At the time, TVA said 83 percent of the waste was sold - mostly as gypsum for wallboard - and only 9.6 percent was landfilled.
In Kingston, less than 1 percent of the waste was sold, according to the report.
The utility's Paradise plant in Paradise, Ky., produced a little more than 1 million tons of coal waste in 2005 and reported selling 33 percent of it - again mostly gypsum - while the Widows Creek plant in Stevenson, Ala., reported 955,500 tons of waste, but sold less than 1 percent.
Widows Creek also was the site of a coal sludge spill this year, just three weeks after the Kingston spill.
This week, the EPA took over cleanup of the Kingston spill under the Superfund law. Ms. Martocci said TVA's agreement with EPA for its oversight in the Kingston cleanup is built around public input.
Now, state regulatory agencies, including the Tennessee Department of Environment and Conservation, control how utilities dispose of coal ash from power plants, and the wastes have been treated as non-hazardous.
Tisha Calabrese-Benton, spokeswoman for the Tennessee Department of Environment and Conservation, said Tuesday that the state's order against TVA, filed in January, requests more information about all of TVA's ash impoundments in the state.
As part of that review, she said, the state asked for stability analysis information for each ash storage site. The information is being analyzed by a contractor, she said.
"We expect preliminary information to be provided to us ... in the next several weeks," she said.
Ms. Calabrese-Benton said the type of coal used makes little difference in the ash that is released from the coal plants.
"The physical characteristics are the same, though there can be different metal profiles based on the source of the coal," she said.
One of the dangers of coal ash is the heavy metal contamination found in it, according to regulators. Those metals include arsenic, beryllium, cadmium, chromium, lead, manganese, mercury and antimony.
An EPA statement says coal ash from Kingston contains arsenic, cadmium, chromium, lead and other toxic chemicals.