Martin County coal slurry spill

The Martin County coal slurry spill was a mining accident that occurred after midnight on October 11, 2000, when the bottom of a coal slurry impoundment owned by Massey Energy in Martin County, Kentucky, broke into an abandoned underground mine below. The slurry came out of the mine openings, sending an estimated 306 million US gallons (1.16 million cubic metres; 1.16 billion litres) of slurry down two tributaries of the Tug Fork River.

Source: Wikipedia — Martin County coal slurry spill (CC BY-SA 4.0)