Worries over boundary water pollution crest in Minnesota and Ontario, as Biden-era mining ban nears reversal

A Minnesota-based wilderness protection group is sounding the alarm that a nearly-overturned mining ban in the U.S. will open the door to copper-sulfide mining — a move they say risks leaking sulfuric acid into shared Boundary Waters at the Canadian border, including Quetico Provincial Park and the Lake Superior watershed in northwestern Ontario.

That ecosystem sprawls across the Minnesota-Ontario border, which sits about 160 km southwest of Thunder Bay. On the US side, it measures about 4450 square kilometres — roughly the size of Woodland Caribou Provincial Park — and is adjacent to about 240 km of the Canadian border.

Recently, Congressional Republicans sent U.S. President Donald Trump a resolution to lift the federal ban on mining near the BWCA, and it narrowly passed Senate last week. Watchers expect the move will clear the final hurdle — a signature from President Trump — and give a subsidiary of Chile-based Antofagasta Minerals the green light to extract copper, nickel and other precious metals at the headwaters of the national forest.

According to Marshall, copper-sulphide mining like that proposed, "creates sulfuric acid, which is chemically the same as battery acid and creates an enormous amount of battery acid that's virtually impossible to contain."