Acid from Copper Mine Tailings

Considering the known risks and dangers associated with every copper mine past and present in the U.S. and Canada, it seems strange we Minnesotans have not been hearing much if anything about them. Meanwhile, Canada’s new PolyMet Mining Company (which has never mined copper before) is quietly forging ahead to obtain rights to mine copper between Hoyt Lakes and Babbitt near the eastern end of the Iron Range in St. Louis County. PolyMet’s Environmental Impact Statement has already been approved by our MDNR but it still must be approved by the U.S. Army Corps of Engineers, the U.S. Forestry Service, the U.S. Environmental Protection Agency and several tribal governments.

What is risky and dangerous about copper mining? Unlike iron, copper and many other metals including nickel is found in sulfide bearing rock. When sulfide bearing rock is dug up and exposed to water (rain or snow) and oxygen, the sulfide turns into sulfuric acid (the same caustic acid used in car batteries).

There are several sources of sulfuric acid in copper mining. One is tailings. Copper mine tailings are piles of sulfide bearing rocks not containing enough copper to make it feasible to extract copper from them. Adjacent to PolyMet’s three planned open pits (in an area 500 football fields in size) will be piles of tailings 20 stories high. Once rain water and oxygen begin percolating down into these piles, nothing can stop sulfuric acid from forming. Though PolyMet plans to place waterproof liners in basins under these piles, the company admits these liners will eventually deteriorate and crack. Sulfuric acid will then pollute surface and ground water and aid in destroying about 1600 acres of surrounding wetlands — the largest permitted destruction of wetlands in Minnesota history. PolyMet also predicts sulfuric acid will eventually overflow from one basin into the adjacent Partridge River (killing everything living in the water). This river flows past the town of Hoyt Lakes into adjacent Colby lake and then into the St.Louis River which finally empties into Lake Superior at Duluth. At every other copper mine in operation in America and Canada today, great volumes of sulfuric acid and other dangerous pollutants have been accidently(?) released into water courses from time to time, ruining 1,118 miles of streams in Montana alone. Numerous containments at the mine site are expected to exceed water quality standards for hundreds to several thousands of years.

This is only the beginning. Watch for more about the dangers of copper mining in my future blog posts

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