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Hard rock mines have a long history of environmental damage, according to the EPA. Agency documents show that sulfide rock mining of various kinds have polluted 10,000 miles of rivers and streams, mostly in the western United States. Between 1998 and 2007, the federal government spent at least $2.6 billion to clean up polluted hard-rock mines, some of which are now Superfund sites.
Mining officials say new technologies and engineering techniques can handle such challenges. In addition to liners for the waste pits, walls and other protections, PolyMet plans to install a state-of-the-art “reverse osmosis” water treatment system for water from its pits during operation. It also plans to recycle the water used in the ore-processing facility. The company says the project will meet all of the state and federal laws governing water quality.
PolyMet spokeswoman LaTisha Gietzen said long-term water treatment is a routine requirement for mines and other facilities like landfills.
“Modern rules and regulations require water quality standards to be met long-term,” she said.
But the waste rock and the mine site can produce pollution long after a mine has stopped producing, a problem that has plagued mines across the country.
The DNR says in the environmental review that PolyMet would be required to operate the reverse osmosis water treatment systems for as long as necessary. PolyMet would also work on developing so-called passive water treatment systems, typically wetlands or other natural features, that at some point could replace the water treatment plants.
Computer projections in the environmental impact statement say that either active or passive water treatment will be needed for 200 years for the mine site, and up to 500 years for the metallurgical site. The document says water treatment would cost between $3.5 and $6 million per year after the mine closes.
“While long term,” the document reads, “These time frames for water treatment are not necessarily perpetual.”
Environmentalists who oppose the project say that with that language, regulators are trying skirt a Minnesota law that specifically prohibits mines requiring perpetual treatment after closing. The statute, passed in the 1990s, requires mines to be reclaimed and maintenance-free, they said.
“That law was written to prevent exactly what they are intending to do,” said Betsy Daub, policy director for Friends of the Boundary Waters Canoe Area Wilderness, an advocacy group.
Richards disagreed. In an e-mail, he said DNR rules allow for active treatment until the state certifies the mine as closed, and there are no time limits for that. Until the DNR says the mine is closed, Richards said, the company will be not released from environmental and financial liabilities.
Josephine Marcotty • 612-673-7394
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