Video: Aerial view of Mount Polley mining pond failure; official report released!

A few months after the extensive destruction at Mount Polley copper and gold mine, the independent panel, responsible for investigating the causes for the release of millions of cubic meters of sludge into the neighboring lakes and rivers of the south-central British Columbia, Canada, issued its 156-page "Report on Mount Polley Tailings Storage Facility Breach". The report was commissioned by the British Columbia Energy and Mines minister. 

Based on the report's conclusions, failure of the tailings pond is attributed to poor design, setting the ground for the failure and the rockfill's steep slope, which activated it. Poor design was a result of the lining absence as well as incomplete subsurface investigations and site characterization process. The second did not identify a continuous GLU (upper glaciolacustrine) layer in the area of the failure. Under the embankment's stresses, the specific layer was prone to undrained failure. Additionally to the embankment's flawed construction, the steep slope of the downstream rockfill zone essentially set off the failure. Contrary to its original design of 2.0 horizontal to 1.0 vertical the slope of the rockfill zone was constructed with a 1.3 horizontal to 1.0 vertical slope. At the time of the failure, works were under way to reduce the zone's slope to meet initial design criteria. 

Watch the video below, with aerial views taken after the failure and access the full report in pdf format here!