Is copper-nickel mining worth the environmental risk?

Rock with copper
Ely, Minn. — A rock alongside a highway near Ely, Minn. shows evidence of copper mineralization Friday, Sept. 27, 2013. (Derek Montgomery / For MPR News)

"Deep below the Superior National Forest floor, traces of copper locked into the rock are stirring up both dreams and dread," write MPR News reporters Dan Kraker and Elizabeth Dunbar.

PolyMet Mining is working to persuade state officials that it can unlock those deposits safely, without causing significant harm to a corner of Minnesota known for its water and wilderness. If it does, 11 other companies waiting in the wings could follow suit, bringing a new kind of mining to the state's Iron Range.

For years, PolyMet has tried to demonstrate its plan would avoid scenarios that infuriate environmentalists. The latest study on how an open pit copper-nickel mine could change the landscape just north of the town of Hoyt Lakes will be released Friday in a 1,800-page environmental impact statement.

It will be a major step for PolyMet, and kick off a public discussion that could help decide if the mine is built and if so, what it looks like. Mining supporters hope the journey will end with hundreds of jobs for a needy region and a spot for Minnesota on a global stage where copper is an essential part of economic progress. It's used in the electrical wiring for new cities in China, wind turbines dotting the Great Plains and new smartphones.

The latest study comes after the U.S. Environmental Protection Agency found an earlier one to be inadequate. Drafts of the environmental impact statement have been circulating for months. The document makes clear that the proposal carries long-term environmental risks different from those posed by iron mining, which has left its mark on northern Minnesota for more than a century. Those risks have given many Minnesotans pause.

The leftover rock has generated most of those concerns. The metals are embedded in rock containing sulfides, which can produce sulfuric acid when exposed to air and water. Because the desirable metals are just specks, the piles of unwanted, potentially toxic rock will quickly multiply.

To avoid leaching acid and heavy metals into water that eventually reaches Lake Superior, all the snow and rain that falls onto those piles and into the open mining pits must be contained and treated, along with any water that leaks from the tailings basin where leftover waste is deposited. It would require a herculean feat of engineering that has never been successfully done before on this scale. [Full story]

Today's Question: Is copper-nickel mining worth the environmental risk?

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