This case study has been prepared solely by GDS Instruments following our review and interpretation of a publicly available technical report. This case study has not been reviewed by third parties, and does not constitute technical advice of any sort.
Early on the 4th of August 2014, an embankment breach occurred at the Mount Polley Mine Tailings Storage Facility (TSF) located in British Columbia, Canada. The cause of the breach, which released millions of cubic metres of tailings slurry and supernatant water (Brown et al., 2016) from the TSF into Polley Lake, Hazeltine Creek, and Quesnel Lake, was subsequently examined by an Independent Expert Engineering Investigation and Review Panel (the Panel). The Panel reported on its findings (Morgenstern et al., 2015) on the 30th of January 2015, concluding that the dominant reason for the breach was embankment foundation soil failing under undrained conditions due to stresses imposed by the embankment construction.
This case study briefly summarises some of the geotechnical engineering findings reported by the Panel. In particular, it focuses on the laboratory testing programme that was critical to the investigation, which utilised an advanced direct simple shear apparatus designed and manufactured by GDS Instruments (GDS). We recommend that our readers refer to the publically available Panel report, published by the Province of British Columbia, for detailed commentary relating to the Mount Polley Mine TSF embankment breach.