"Half would go for long-term water treatment after copper-nickel mine closes."

"PolyMet Mining Corp. would have to put up roughly $1 billion dollars halfway through the life of its proposed copper-nickel mine in northern Minnesota to protect state taxpayers from environmental risks — with more than half the funds dedicated to a trust fund for water treatment that would be required long after the mine has closed.

The estimate by state regulators, obtained by the Star Tribune through a data practices request, for the first time puts a dollar amount on the significant risks to water, air and wildlife that come with a new kind of mining for Minnesota.

The peak-mining cost estimate is three times higher than what PolyMet first proposed a year ago, and approximates what outside engineering experts have recommended because of the scale and severity of potential water contamination from hard-rock mining."

Josephine Marcotty report for the Minneapolis Star Tribune December 20, 2017. [2]