Imperial Metals reported that British Columbia’s Ministry of Energy and Mines and Ministry of Environment have issued the necessary authorizations for Imperial’s Mount Polley open-pit copper-gold mine in south-central British Columbia to return to normal operations based on use of its repaired and buttressed tailings storage facility (TSF).
The TSF at Mount Polley suffered a massive breach on August 4, 2014. Over the past two years, management and staff have worked in close cooperation with regulatory agencies, First Nations, and members of the local communities to repair and buttress the TSF, following the Best Applicable Practices identified in an Independent Expert Engineering Investigation and Review Panel report.
A number of important conditions and milestones were met by Mount Polley as it worked toward receipt of the regulatory authorizations required to return to normal operations. Thorough investigations by the Review Panel, the Ministry of Energy and Mines, and a team from Golder Associates Ltd. (the engineer of record retained by Mount Polley) all concurred on the failure mechanism that led to the breach of the TSF embankment. The updated design of the embankment in the specific area of the breach reflects the results of these investigations.
Furthermore, all of the TSF’s other embankments were investigated, and foundation conditions throughout were comprehensively characterized. These investigations led to modification of the embankments to assure that the stability of the structure meets or exceeds all applicable legislative requirements and guidelines. Imperial notes that use of the existing TSF was recommended after an assessment of alternative sites and technologies.
Research and monitoring to date indicate that the downstream environment is recovering rapidly from the breach. No long-lasting impacts are anticipated at this time.
Imperial Metals President Brian Kynoch said, “A return to normal operations is important to the region, as Mount Polley is a significant contributor to the economy, directly providing approximately 350 jobs, as well as supporting the local communities of Likely, Williams Lake, and the surrounding region. Mount Polley is committed to working with First Nations and local communities to complete rehabilitation of the areas impacted by the breach, and we thank all those involved in the rehabilitation for the excellent work that has been completed to date.”
Mount Polley mine operations were suspended following the 2014 tailings breach, but were restarted at a reduced level of operation in August 2015. The mine’s production from January 1 to August 4, 2014, (prior to the breach) totaled 24.5 million lb of copper, 25,900 oz of gold, and 74,770 oz of silver in concentrate. Its production from August 5 to December 31, 2015, totaled 8 million lb of copper, 15,200 oz of gold, and 25,911 oz of silver in concentrate.