Muddy waters: After Mount Polley, miners and engineers grapple with the risk of maintaining the status quo -by Eavan Moore (CIM Magazine – November 2015)

Six months before the Mount Polley tailings dam failure in August 2014, a tailings facility in North Carolina released toxic coal ash into the Eden River. One month after Mount Polley, three workers died in a tailings facility failure at the Herculano mine in Brazil. An unusually bad year? Not necessarily.

According to a July 2015 report by David M. Chambers, president of the Center for Science in Public Participation, and Lindsay Bowker, a Maine-based activist with a background in civil construction projects, between 1990 and 2010 there were 33 dam failures that released more than 100,000 cubic metres of “semi-solid discharge” and/or caused loss of life. Based on historical trends, the report predicts 11 more will have occurred by 2020.

In January 2015, a three-person panel appointed to investigate the origins of the Mount Polley tailings spill came to similar, albeit less drastic, conclusions. “If the inventory of active tailings dams in [British Columbia] remains unchanged, and performance in the future reflects that in the past, then on average there will be two failures every 10 years and six every 30,” the panel wrote. “In the face of these prospects, the Panel firmly rejects any notion that business as usual can continue.

Mining companies, engineering consultants, investors, regulators and the public at large must now determine how “business as usual” should be changed, and by whom.

The Mount Polley breach started quite a few conversations in Canada, according to panel member Dirk van Zyl, also a mining engineering professor at the University of British Columbia. “You really have a number of corporate tailings engineers sitting around the table saying, ‘What do we do so that what happened at Mount Polley does not happen again?’”

Water management

One obvious line of inquiry looks precisely at the nature of the disaster at Mount Polley: almost 25 million cubic metres of water, tailings and “interstitial” water broke through its dam and was then carried into the Quesnel and Cariboo river systems. This type of breakage is an inherent risk with conventional water-filled impoundments.

“It’s almost certain that in the long term, these tailings facilities will fail,” said van Zyl. The panel called for the mining industry to phase out water covers completely.

KGHM Ajax, a prospective mine developer near Kamloops, British Columbia, heeded the panel’s call to revisit its tailings plan. The company had planned to submit an environmental assessment application in 2015 that included a conventional water-covered storage facility, with tailings deposited as slurry with 68 per cent moisture content. But in response to the panel’s report, Ajax commissioned a new tradeoff study re-exploring its options.

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