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Didn't say 'the worst', said one of the worst and it is.

And no, not just a bunch of rocks.

The sequestered mine tailings will leach acid whenever they are exposed, the impoundment will need to be maintained forever to protect downstream waters. 

The mine is expected to produce around 88 million tons of mine tailings if operation continues through 2031.

Active water treatment and tailings repository maintenance will be needed forever to prevent heavy metals and sulfuric acid discharge into downstream waters.

The mine tailings pond needs to be maintained at an appropriate level in perpetuity, requiring regular inspections, maintenance, and treatment of over a billion gallons of discharged water every year.  

The treatment of the water is expected to produce almost 70,000 tons of sludge every year that will be buried in the mining pit for the next 50-100 years.

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In addition to the pollution, the Canadian mining corporation has been fined for violation repeatedly.
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