She says in the months since the August 2014 breach, the Mine has completed significant repairs and reinforcement work on the TSF.
“More than 2.5 million tonnes of materials have been used to construct a buttress around the main and perimeter embankment since the breach occurred. With the addition of the buttress, the factor of safety for the tailings storage facility has increased from less than 1 to a factor safety of now 1.5.”
Under the permit amendment, the mine is authorized to process up to 22,450 metric tonnes of ore per day and store tailings in the repaired and strengthened TSF.
The permit amendment also authorizes the Mt. Polley to continue operations in previously permitted areas of the Cariboo Pit and underground workings.
Prior to approval, the company’s Mines Act permit amendment application underwent a lengthy 8-month review process, including a thorough geotechnical review, a 30-day public consultation period and a detailed technical review by members of the mine development review committee (MDRC). The MDRC
consisted of representatives from provincial agencies, First Nations, local governments (the City of Williams Lake and Cariboo Regional District), the community of Likely, the Department of Fisheries and Oceans and Environment Canada.
The geotechnical review was completed by two senior geotechnical engineers and both found that the proposed design and construction of the repaired Tailing Storage Facility met appropriate engineering standards for tailings facilities.
As a condition of the Mines Act restricted re-start permit amendment authorized on July 9, 2015, the Mine must now submit a draft technical assessment report in support of the long-term water management plan by June 30th in order to continue operations.