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The Trouble With Tailings: Toxic Waste ‘Time Bombs’ Loom Large Over Alaska’s Salmon Rivers
There are a few unarguable truths about mine tailings, the pulverized rock, water and sludge left over from mineral extraction — mining is a messy business, the leftovers have to be dealt with forever and it’s impossible to guarantee against another tailings dam failure such as the Mount Polley catastrophe.
In B.C., there are 98 tailings storage facilities at 60 metal and coal mines, of which 31 are operating or under construction and the remaining 67 are at mines that are either permanently or temporarily closed
That means communities throughout B.C. and Alaska are looking nervously at nearby tailings ponds, which sometimes more closely resemble lakes, stretching over several square kilometres, with the toxic waste held back by earth and rock-filled dams. The water is usually recycled through the plant when the mine is operating, but, after the mine closes, water, toxins and finely ground rock must continue to be contained or treated.
It’s the realization that tailings have to be treated in perpetuity that worries many of those living downstream, especially as the Mount Polley breach happened only 17 years after the dam was constructed.
“The concept of forever boggles people minds. In one thousand years is the bank account still going to be there? These people are going to be dead,” said Chris Zimmer of Rivers Without Borders.
“There are time-bombs up there without a plan to deal with them. Are they going to be able to build a mine that’s going to keep its integrity forever?”
It raises the question of whether there should be any mining in an area that is vital to five species of salmon and sustains the livelihoods of so many Alaskans, said Heather Hardcastle, a Juneau fisherman and coordinator of Salmon Beyond Borders.
“This is why this region of the world is so globally significant and why we care so much,” said Hardcastle, who is among those pushing for the issue to be referred to theInternational Joint Commission.
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Mount Polley spill blamed on design of embankment
Independent investigation finds foundation of earthen dam failed because of unstable underlying layers
An independent investigation has determined the breach of the Mount Polley mine tailings dam in B.C. was caused by a failure to detect a weak layer in its foundation, likening the massive embankment to a “loaded gun.”
The report, which was released on Friday morning in Victoria, said the design failed to take into account the complexity of the instability of underlying glacial and pre-glacial layers under the retaining wall.
But the authors, geotechnicians Norbert Morganstern and Steve Vick, did not blame provincial inspectors for not detecting the problem beforehand.
The investigators said the dam was built on a weak layer of glacial deposits that was undetected at the time, making the dam like a ‘loaded gun.”
They said the construction of a steep slope in the embankment as the dam was raised was “like pulling the trigger,” causing the failure last summer.
They also concluded that massive volume of water in the tailings dam did not cause the dam to fail, but it did result in more tailings being released when it did breach.
Just eight days before the dam failed, a plan was approved to raise the dam further, but on the condition that a buttressing wall was put in place and the slope decreased, they said.
The investigators also made several recommendations to improve the safety of tailings dams, including updating the way they are designed, monitored and regulated in B.C.
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