Understanding the tailings ponds breach at Mount Polley near Likely, B.C., which has emptied mine waste into waterways
On Monday, an Imperial Metals tailings pond in B.C. breached its embankment, spilling contaminated water and waste material into the surrounding waterways and spurring a state of emergency in the area. It’s raised the ire of First Nations groups, who say the company ignored a report that the growth of the pond was unsustainable.
It’s angered environmental groups, furious at the suggestion that water with arsenic and mercury was released into the lakes. But what exactly are tailings ponds? Does the industry have an alternative? We talked to Scott Dunbar, the head of the University of British Columbia’s school of mining engineering, to explain the issues at play and the institutional attitudes that need to change so this doesn’t happen again.
Q: So what is a tailings pond, and how does it work?
When you take the rock out of the ground, you grind it up to particles about the size of sand and silt, then you run it through what they call a concentration plant and it separates the minerals of interest from the waste. The waste becomes tailings, and it gets mixed up with water, and it’s pumped out into this pond. The purpose of this pond, with an embankment around it, is to retain the tailings and allow them to drain as much as possible. It’s basically sand-sized particles, but there’s an awful lot of it that’s produced relative to the minerals that generate all that cash. This waste that has to be dealt with. It’s mostly silicates. If the filtering is done well, which it usually is, there would be very few metallics.