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Mount Polley Tailings Breach

Last updated on August 11, 2021

On August 4, 2014, a breach occurred at the tailings storage facility (TSF) at the Mount Polley mine near the town of Likely. Shortly afterwards, three separate investigations into this incident were launched: an independent expert engineering panel was established to determine the root cause of the breach, the Chief Inspector of Mines conducted an investigation, and the British Columbia Conservation Officer Service is conducting an investigation.

Both the expert panel and the Chief Inspector found that the Mount Polley tailings dam failed because the strength and location of a layer of clay underneath the dam was not taken into account in the design or in subsequent dam raises. The Chief Inspector also found other factors including the slope of the perimeter embankment, inadequate water management, insufficient beaches and a sub-excavation at the outside toe of the dam exacerbated the collapse of the dam and the ensuing environmental damage. 

The Province has now addressed all of the recommendations from the independent expert panel and most of the Chief Inspector of Mines recommendations from the investigations into the Mount Polley TSF breach. In July 2015, Minister of Energy and Mines Bill Bennett appointed a committee to review the Health, Safety and Reclamation Code for Mines in British Columbia (the Code) to determine how best to implement the 26 recommendations stemming from the independent expert engineering panel and the Chief Inspector of Mines’ investigations.

Independent Expert Engineering Panel

The independent expert engineering panel has completed their investigation on the root cause of the Mount Polley breach and presented their findings on January 30, 2015.

Chief Inspector of Mines' Investigation

The Chief Inspector of Mines has completed his investigation into the Mount Polley breach and presented the findings on December 17, 2015. The investigation report contains the process and findings of the investigation and the 19 recommendations made by the Chief Inspector of Mines.

Conservation Officer Investigation

The Conservation Officer Service investigation into the Mount Polley breach is ongoing.

Approval to Return to Full Operations

On June 23, 2016, Mount Polley Mining Corporation received a Mines Act permit amendment allowing for a return to full operations at the Mount Polley mine. The application was approved following a technical review process with the Cariboo Mine Development Review Committee as well as a public comment period.

The public notification was advertised by Mount Polley Mining Corporation in the BC Gazette and Williams Lake Tribune. Hard copies of the application were available in the Likely, Williams Lake and Big Lake libraries.