Mines in British Columbia have responded to an order by the chief inspector of mines to confirm whether foundation materials similar to those at Mount Polley exist below any of their dams and no immediate risks or safety concerns were identified.

Immediately following the release of the independent panel report and recommendations on the Mount Polley tailings storage facility failure, the chief inspector of mines ordered 38 mines to undertake an assessment to determine if any of the dam(s) associated with their tailings storage facilities (TSFs) may be at risk due to:

• Un-drained shear failure of silt and clay foundation – whether Glaciolacustrine (GLU) foundation materials, similar to those at Mount Polley, exist below any of their dams.
• Water balance adequacy – outline current and long-term water management plans.
• Filter adequacy – identify internal dam erosion prevention methods and other means to prevent piping and cracking.

The order applied to all B.C. mines with an operating TSF, or a non-operating TSF with a dam safety classification of significant or higher.

The Ministry of Energy and Mines received letters of assurance from 35 mines on or before the June 30, 2015, deadline. The chief inspector of mines granted extensions to three non-operating mines:

• Klondike Silver/Silvana Mine – response required on or before Oct. 15, 2015.
• Carolin/Ladner Mine – response required on or before Oct. 30, 2015.
• Shasta Mine – response required by spring 2016.

Copies of the letters of assurance are available online at: http://www2.gov.bc.ca/gov/content/industry/mineral-exploration-mining/dam-safety-inspections-2014

A total of 14 mines reported having dams with (GLU) in their foundation materials. There were four TSFs out of 32 at the mine sites that were unable to confirm that dam design specifically accounted for GLU. The four TSFs are closed and the mining companies responsible for them are taking appropriate measures to determine what, if any, work may be needed to address the GLU. The four TSFs are located at the following mines:

• Beaverdell Mine – TSF closed since 1991.
• Highland Valley Copper Mine – Bethlehem TSF has been closed since 1983 and is not used by the mine.
• Pinchi Lake Mine – ceased operation in 1975 and substantial reclamation and site closure works were completed in 2010 and 2011. There is no water storage at the TSF.
• Sullivan Mine – ceased operations in 2001. The mine’s TSFs did not have similar foundation conditions to those found at Mount Polley. Silt layers were noted at one borehole at the Sludge Pond South Dyke. Engineer determined no further action is needed at this site as there are no construction/operational triggers for an un-drained failure to occur at site.

Under the order, mines were asked to provide a work-plan and schedule to address any information gaps identified during the assessment. Based on the reviews and findings provided by the professional engineers, 26 mines identified areas where more information should be compiled and all sites have committed to completing the work necessary – this work includes further analysis and information gathering on all three areas subject to the order (GLU, water balance and filter). The ministry will follow-up on the progress of these mines in January 2016.