On August 4, 2014, Mount Polley Mine in British Columbia, Canada, made international news when a dam failure released millions of cubic meters of tailings—hazardous by-products of mining operations—into the watershed. Much of this toxic slurry surged into nearby Quesnel Lake, forming a layer of fine sediment up to 15 meters thick on some parts of the lake floor.
Click here for original story, The fate of a lake after a dramatic mining disaster
Source: Phys.org