Kingston Fossil Plant coal fly ash slurry spill
The Kingston Fossil Plant Spill was an environmental and industrial disaster that occurred on December 22, 2008, when a dike ruptured at a coal ash pond at the Tennessee Valley Authority's Kingston Fossil Plant in Roane County, Tennessee, releasing 1.1 billion US gallons (4.2 million cubic metres) of coal fly ash slurry. The coal-fired power plant, located across the Clinch River from the city of Kingston, used a series of ponds to store and dewater the fly ash, a byproduct of coal combustion.
Source: Wikipedia — Kingston Fossil Plant coal fly ash slurry spill (CC BY-SA 4.0)