Debate over the need for long-term water treatment has dominated public testimony surrounding PolyMet's proposed copper-nickel mine, but the agencies studying the plan didn't ask the one question seemingly everyone wants the answer to: How long exactly will that treatment be needed?
The environmental impact statement prepared by the Minnesota Department of Natural Resources and several federal agencies sidesteps the issue. Still, two figures used in their modeling studies — 200 years and 500 years — have come up as a frequent rallying cry among those speaking out against the project at the first two public meetings, and there's sure to be additional references to those figures during the third and final public hearing on the proposal Tuesday in St. Paul.
"Trading 500 years worth of mining pollution for 20 years worth of jobs is irresponsible," argued Hillary Peterson of Sturgeon Lake, during the hearing in Duluth earlier this month.
PolyMet and its supporters have taken issue with how opponents are using the figures.
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"I would like to ask the DNR to make an official statement as to whether or not this claim of 500 years of required wastewater treatment post closure is in the [supplemental draft environmental impact statement], or is it not," Jay Lehman, of Aurora, said during the second public hearing on the Iron Range. "This issue needs to be put to rest for the sake of properly informing the public."
The confusion emerged in part because of the preliminary draft of the environmental impact statement PolyMet critics obtained through data practices requests.
"I can understand where some of the confusion comes from. In fact, in one of the preliminary drafts we didn't have the wording quite right on this issue," said Steve Colvin, deputy director of the DNR's Division of Ecological and Water Resources who is overseeing the EIS.
That preliminary draft stated that water flowing through the mine site would need to be captured and treated for at least 200 years to meet the state's water quality standards. It gave a 500-year minimum for the plant site. It appeared in media reports and has been repeated by mining opponents many times.
But Colvin said it was an error that was corrected in the latest draft to reflect the question officials were asking: Would capturing and treating 90 percent of water at the mine and plant sites ensure that the other 10 percent of polluted water that escapes still meets state water quality standards?
"It's kind of a paradigm shift," Colvin said. "Most people would normally expect that the model would predict how long something would be a problem, but yet, we came in with an assumption that it would be a problem for a long time, so we were interested in answering a different question with the model."
DNR and PolyMet officials said the answer to that question, even centuries later, is yes. The 200- and 500-year figures remain in the document, because that's how far out the models were run, they said.
So why not estimate how long water treatment would be needed? PolyMet officials said it's very uncertain, and they say they won't know enough about potential contaminants until they begin unearthing them and monitoring their impact.
"The real data will give us a much better idea of what the future looks like," said Jennifer Saran, PolyMet's director of environmental permitting and compliance.
She said estimating how long water treatment will be needed is beside the point because the company will offer financial guarantees to treat polluted water — forever if necessary.
"We're prepared for treating the water for as long as it takes, and financially assuring the money that it would take to treat that water, and we know the treatment works to meet water quality standards so that the time frame is not really something that we have to know," she said.
The environmental groups challenging the project, though, are skeptical.
"The question is, is this something we feel comfortable with? A need to treat water pollution at a mine that has been closed for centuries, for 20 years of operations? Is that something we want to take on?" asked Betsy Daub, policy director for Friends of the Boundary Waters Wilderness.
Daub and other critics have pointed to graphs deep within the thousands of pages of data referenced in the study that appear to show water flowing into a treatment plant centuries from now would still be too toxic to release into the environment without that treatment.
But because the study focused on the water that could escape rather than water contained at the site, other factors would have to be considered to give a true estimate of how long treatment would be needed, said Brad Moore, PolyMet's executive vice president of environmental and governmental affairs.
He said company officials expect mechanical treatment, such as the reverse osmosis systems PolyMet is proposing for the mine and plant sites, would only be needed for decades. The effectiveness of passive treatment techniques such as wetlands is still being studied.
"Instead of having to debate over that both with proponents and opponents, let's instead use a proven technique — mechanical treatment such as reverse osmosis — and make sure there's adequate financial assurance so that's used as long as it takes," Moore said.
The EIS doesn't provide details on how PolyMet would pay for water treatment or how state officials can be confident they've required enough financial guarantees. If the project moves forward, the DNR will take up those questions during the permitting phase.
But the uncertainty within the environmental study — and an understanding that treatment costs could exist forever — should give state officials pause as they decide whether to take on the risk, said Kathryn Hoffman, an attorney with the Minnesota Center for Environmental Advocacy.
"They have not been able to describe an end scenario for treatment of pollution at these sites," Hoffman said.