Elsevier

Applied Geochemistry

Volume 91, April 2018, Pages 64-74
Applied Geochemistry

Water quality impacts and river system recovery following the 2014 Mount Polley mine tailings dam spill, British Columbia, Canada

https://doi.org/10.1016/j.apgeochem.2018.01.012Get rights and content
Under a Creative Commons license
open access

Highlights

  • The Mount Polley mine tailings embankment breach is the second largest on record.

  • Spatial patterns in trace metal cycling were studied in Hazeltine Creek.

  • Water quality impacts are considered low with Cu and V the only elements of concern.

  • Chalcopyrite oxidation and Fe oxide reduction are Cu mobilization mechanisms.

  • Swift removal of spilled tailings can limit chemical impacts in watercourses.

Abstract

The Mount Polley mine tailings embankment breach on August 4th, 2014, in British Columbia, Canada, is the second largest mine waste spill on record. The mine operator responded swiftly by removing significant quantities of tailings from the primary receiving watercourse, stabilizing the river corridor and beginning construction of a new river channel. This presented a unique opportunity to study spatial patterns of element cycling in a partially-restored and alkaline river system. Overall, water quality impacts are considered low with Cu, and to a lesser extent V, being the only elements of concern. However, the spatial pattern of stream Cu loading suggested chemical (dominant at low flow) and physical (dominant at high flow) mobilization processes operating in different parts of the watershed. Chemical mobilization was hypothesized to be due to Cu sulfide (chalcopyrite) oxidation in riparian tailings and reductive dissolution of Cu-bearing Fe oxides in tailings and streambed sediments whereas physical mobilization was due to erosion and suspension of Cu-rich stream sediments further downstream. Although elevated aqueous Cu was evident in Hazeltine Creek, this is considered a relatively minor perturbation to a watershed with naturally elevated stream Cu concentrations. The alkaline nature of the tailings and the receiving watercourse ensures most aqueous Cu is rapidly complexed with dissolved organic matter or precipitates as secondary mineral phases. Our data highlights how swift removal of spilled tailings and river corridor stabilization can limit chemical impacts in affected watersheds but also how chemical mobilization (of Cu) can still occur when the spilled tailings and the receiving environment are alkaline. We present a conceptual model of Cu cycling in the Hazeltine Creek watershed.

Keywords

Mount Polley
Mine waste
Tailings
River restoration
Water quality
Copper

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