THE LONG-TERM ENVIRONMENTAL IMPACTS OF THE MOUNT POLLEY MINE TAILINGS SPILL, BRITISH COLUMBIA, CANADA (Invited Presentation)

On 4^th August 2014, the failure of the Mount Polley mine waste storage facility in British Columbia, Canada, released ~25 Mm³of mine waste into the Quesnel River Basin, one of the most pristine freshwater ecosystems on earth. The accident was one of the largest of its kind ever documented and received global media coverage. The waste stream overwhelmed Hazeltine Creek, causing it to expand from 2 m to 150 m in width and stripped all trees in a 9 km long corridor along the creek. The volume of the tailings released caused Polley Lake water level to rise by 1.7 m.

Among impoundment failures, the Mount Polley disaster is unique in that the solid tailings contain an unusual mixture of metal contaminants (As, Cu, Au, Mn, Ni, Pb, V). The environmental risk posed by the spilled tailings is confounded by the location of the spill in a mountainous forested catchment, affected by severe winters with prominent spring snow melts that have the potential to remobilise very large quantities of spilled tailings.

In this study, we adopt a multidisciplinary approach to determine the geochemical and geomorphological impacts of the tailings spill. We have two specific objectives. (1) The physicochemical speciation and geochemical stability of spilled tailings will be characterised in surface and hyporheic sediments using bulk chemistry, mineralogical (XRD and SEM) and speciation methods (sequential extractions, electron microprobe analysis, XAS). (2) Pre- and post-remediation geomorphological assessments will use unmanned aerial vehicle (UAV) photographic surveys and ground-based topographic surveys to establish the efficacy of remediation efforts in stabilising Hazeltine Creek channel and to quantify the physical remobilisation of tailings during the spring snowmelt.