On the night of August 3-4, 2014, the dam enclosing the tailings storage facility (TSF) at Mount Polley Mine, a copper and gold mine in interior British Columbia, failed. Over the next 16 hours, the failure led to a progressive breach of the Perimeter Embankment of the dam, releasing over 21 million cubic metres of water and mine tailings into the surrounding environment and watercourses.