Cleanup of the worst spill of its kind in the history of the U.S. is continuing in east Tennessee, where an earthen retention wall at the Tennessee Valley Authority’s Kingston coal plant failed on Dec. 22. The failure sent 5.4 million cu yd of toxic sludge composed of fly ash and water flowing over 300 acres.
The sludge, a byproduct of coal combustion, was stored at a 40-acre waste pond, one of three at TVA’s Kingston plant, located about 40 miles west of Knoxville in Roane County, Tenn., near the Clinch, Emory and Tennessee rivers. No one was seriously injured, but the initial spill, described as “a tidal wave” by the U.S. Environmental Protection Agency, destroyed three homes and ruptured a major gas line.
The cause of the failure is unknown, but TVA officials say rain and freezing temperatures may have contributed. The pond was impounded by 60-ft-high retention walls consisting of clay and bottom ash, according to TVA.
“We’ve got a root-cause investigation team, but most of our efforts are in trying to restore area,” says TVA spokesman John Moulton in Knoxville. A TVA inspection conducted last year found “wet spots,” indicating minor leaking but “no significant problems found that indicated that the dikes were unstable to the point of failure,” he says.
But Jack Sparado, a former federal Mine Safety and Health Administration engineer, says the inspection report indicates serious problems that TVA should have addressed. He conducted the engineering analysis of a similar 300-million-gallon coal-slurry spill in Martin County, Ky., in 2000 and wrote the engineering report of the Buffalo Creek, W.Va., coal-slurry spill that killed more than 100 people in 1972. He offered his comments after reading the Kingston inspection report, which is in the public domain.
Sparado says the dike has been failing since 2003 because of foundation piping, or internal erosion. There had been two minor blowouts in recent years and TVA noted seepage. The agency took corrective measures, but the only solution would have been to drain the reservoir and reconstruct the impoundment, Sparado claims.
“It was completely irresponsible of TVA to allow the dam to continue to be used when they knew of these previous problems,” he says. “They should have done a complete stability analysis of the whole dam and essentially reconstructed it. It certainly should have been engineered better than it was.”
Ronald Hall, Kingston plant manager, says that other than the blowouts, TVA had “no indication or concerns leading up to the event.”
On Dec. 29, TVA Inspector General Richard Moore announced a review of the cause, response and what TVA can do to prevent similar spills at its other facilities. Kingston is one of TVA’s largest coal plants, with nine units and total capacity of 1,700 MW. The plant consumes 14,000 tons of coal daily.
Kingston produces about 2.2 million tons of byproduct a year from emissions-controls equipment. Fly ash, which includes heavy metals such as arsenic, lead, barium, chromium and manganese, is placed into a settling pond. Sludge is then dredged and placed in an on-site landfill, according to a spokeswoman for the Tennessee Dept. of Environmental Control. TDEC issued the permits for the plant’s landfill and water-discharge systems.
The fly-ash pile, towering 55 ft above the retention pond’s water level prior to the failure, was within permit levels, TVA says. EPA classifies fly ash as a solid, rather than a hazardous waste.
Environmentalists and others say the material is cancer-causing and dangerous. “It is toxic regardless of what TVA says,” Sparado says.
TVA will not continue to use the wet ponds at the Kingston plant. “We’re going to go to dry stacking or offsite storage,” Hall says.
Almost 70 pieces of heavy machinery, including bulldozers, skimmer booms, vacuum trucks and amphibious track hoes, and more than 150 people are working to clean up the spill, Hall says. Some dry material is being bulldozed back into the containment area, while the sludge is being put elsewhere to dewater. TVA is using its own heavy-equipment division and has contracted with numerous local contractors, Hall says.
Near the plant, crews are building a 500-ft-long subsurface weir in the Emory River to catch any remaining debris, while booms skim silica. Nearby waterways will be dredged.
EPA, TDEC and TVA are conducting regular water and air testing. EPA reported elevated levels of arsenic and heavy metals and warned people should not drink untreated river water. The agencies also warn that direct contact with the fly ash should be avoided, and children and pets should be kept away from the affected area.
TVA has no estimates on what the cleanup will cost.