| Risk management The database comprises 86 mine sites that currently,
or are proposed to, contain at least one TSF, and this was used to create a publicly available, interactive online British Columbia Mine Tailings Map. A report authored by Dr Steven Emerman also evaluated the database and the risks of a tailings dam failure (based on assessing the combination of the probability and consequence of failure). “The purpose of the map was to establish the
landscape of current and future TSFs across BC,” said Adrienne Berchtold, Ecologist and Mining Impacts Researcher at SkeenaWild Conservation Trust. “We wanted to provide that information publicly and easily regarding TSF location and risk factors. We also wanted to assess trends in BC tailings storage and determine whether the associated risks are changing.” Described as being full of lots of different functionalities and information, it is hoped that the map “will be a useful tool for people to take their own lessons from”. For each site on the map, details on the following
key risk indicators are provided: ● Operational status – Sites that are closed and under care and maintenance may not receive adequate oversight to prevent tailings dam failures. Proposed sites show the emerging tailings landscape in BC, and the risks associated with it.
● Number of tailings dams – Every tailings dam on a site carries its own risk of failure, so more dams convey increased risk.
● Tallest tailings dam height – Taller tailings dams tend to have greater failure consequences and, in some circumstances, have increased probability of failure. However, the failed Mount Polley Dam was only ~40m tall.
● Highest dam failure consequence rating assigned to any tailings dam on site. Dam failure consequence
ratings are assigned on the basis of potential loss of life and potential environmental, cultural, and economic impacts in the event of a failure.
● Upstream dam present indicates whether upstream dam construction has been used to build any tailings dam on site.
● Current tailings storage volume – Larger stored volumes of tailings tend to result in greater failure consequences.
● Design storage capacity for the largest (greatest volume) tailings storage facility. “What we have learned from this map,” Berchtold explained, “is that there is accumulative risk arising through all of these facilities across the province.”
Expert analysis Dr Steven Emerman’s analysis of the database looks at
the risks of failure at the 172 dams holding back mine processing waste in BC. He found that the height and volume of tailings storage facilities across the province have been increasing exponentially over time. The total volume of tailings currently being stored at BC mines is estimated to be 2.5 billion cubic metres and, with the addition of 11 proposed new mines, this is expected to increase by 75%. Operating TSFs are on average nearly twice as high as closed facilities or those under care and maintenance status, with proposed facilities on average again twice as high as operating facilities. Operating facilities hold on average five times more tailings than facilities in closed and care and maintenance status, while proposed facilities would hold on average three times more than operating facilities. With such an increase in height and volume, there has been a corresponding increase in the potential severity of consequences of tailings dam failures, including the potential for loss of human life.
Above: Nearly two-thirds of mining sites in British Columbia with tailings facilities are located in salmon habitat. A major tailings failure could significantly harm salmon and their habitat
f
Below: Tailings Pond from the Highland Copper Mine in British Columbia. Mining has a long history in Canada and continues to play an important role across the country
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