The TVA Tennessee coal sludge spill occurred on December 22, 2008, when hundreds of millions of gallons of coal fly ash slurry escaped after an earthen dike broke at a 40-acre (16 ha) waste retention pond, one of three at the Tennessee Valley Authority's Kingston Fossil Plant in Roane County, Tennessee. The coal-fired power plant, located in the city of Kingston, uses retention ponds to store the slurry, an aqueous mixture of water with fly ash, a byproduct of coal combustion. The sludge traveled downhill, covering up to 400 acres (160 ha) of the surrounding land, damaging homes and flowing into nearby waterways such as the Emory River and Clinch River (tributaries of the Tennessee River). It was the largest fly ash slurry spill in United States history.

Toxicological Perspective

Possible contamination with mercury and other metals.

References

TVA ash flood - wikipedia