Mount Polley mine disaster
 24 July 2014  5 August 2014
NASA aerial photos of the Mount Polley Mine site before and after the dam breach
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| Date | 4 August 2014 |
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| Location | Quesnel Lake, British Columbia, Canada |
| Coordinates | 52°30′48″N 121°35′47″W / 52.513437°N 121.596309°WCoordinates: 52°30′48″N 121°35′47″W / 52.513437°N 121.596309°W |
| Cause | Failure of tailings pond dam |
| Footage | Footage: Youtube |
The Mount Polley mine disaster is an environmental disaster in the Cariboo region of central British Columbia, Canada, that began 4 August 2014 with a breach of the Imperial Metals-owned Mount Polley copper and gold mine tailings pond, releasing its water and slurry with years worth of mining waste into Polley Lake. The spill flooded Polley Lake, its outflow Hazeltine Creek, and continued into nearby Quesnel Lake and Cariboo River. By 8 August the four square kilometres sized tailings pond had been emptied of the majority of supernatant (process water) that sits atop the settled solids (mining waste, or 'tailings'). Water tests showed elevated levels of selenium, arsenic and other metals similar to historical tests before the disaster. The cause of the dam break has been investigated with a final report published 31 January 2015. Imperial Metals had a history of operating the pond beyond capacity since at least 2011.
The Mount Polley open pit copper and gold mine disaster in the Cariboo region of British Columbia began in the early morning of 4 August 2014 with a partial breach of the tailings pond dam, releasing 10 million cubic metres of water and 4.5 million cubic metres of slurry into Polley Lake. The slurry of tailings and process water carried felled trees, mud and debris and "scoured away the banks" of Hazeltine Creek which flows out of Polley Lake and continued into the nearby Quesnel Lake. The spill caused Polley Lake to rise by 1.5 metres (4.9 ft). Hazeltine Creek was transformed from a 2-metre-wide (6.6 ft) stream to a 50-metre-across (160 ft) "wasteland"* and Cariboo Creek was also affected. As of 8 August 2014, a "slurry of toxic water and mud" continued to pour into the once pristine Quesnel Lake, the cleanest deep water lake in the world. By the end of the day the four square kilometres sized tailings pond was "virtually empty". Mine safety experts and media articles have called the spill one of the biggest environmental disasters in modern Canadian history. British Columbia’s government initially insisted the dam failure was not an environmental disaster, a position British Columbia’s Environment Minister, Mary Polak, reversed in November 2014.
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Wikipedia