Water flow underestimated for PolyMet study

The amount of water flowing under and near the proposed PolyMet copper mine was significantly underestimated for computer models used to determine the environmental impact of the project, new information has revealed.

The PolyMet project still is in the environmental review phase. (2006 file / News Tribune)

The amount of water flowing under and near the proposed PolyMet copper mine was significantly underestimated for computer models used to determine the environmental impact of the project, new information has revealed.

According to a Minnesota Department of Natural Resources internal memo from Dec. 17, obtained with a state data practices request, the DNR concludes that the so-called "base flows" for the mine site are two to three times higher than initially estimated by PolyMet.

At one place, where the Partridge River flows past Dunka Road, stream flow was measured between 1.3 and 1.8 cubic feet per second. PolyMet had estimated 0.5 CFS.

For several years, scientists for tribal natural resource agencies have been telling PolyMet and the DNR that the flow numbers were too low and didn't reflect reality. They said the discrepancy makes computer model predictions about the project's impact inaccurate, from water pollutants to wetland impacts.

Only in mid-2011, however, was a gauge installed to actually measure flow in one spot, well after the current environmental review document was being finalized.


"There's a string of emails on this issue that goes back to 2008. I'm not sure why they waited this long into the process to admit they had a problem with flow rates that we've been pointing to for so long,'' said Nancy Schuldt, water projects coordinator for the Fond du Lac Band of Lake Superior Chippewa. "From my perspective, if you have the wrong information to start with, this has the potential to change several of their predicted outcomes."

Schuldt said tribal scientists are scheduled to meet with DNR and federal regulatory officials on Monday to discuss the groundwater discrepancies among several other issues that tribal officials say are major deficiencies in the environmental review document.

Many of those deficiencies were included in the depths of the 2,169-page environmental review document, in a dissenting opinions section. Based on the memo, however, the DNR now appears to be agreeing with the tribes that the water flow estimates were wrong.

Steve Colvin, who heads the PolyMet review for the DNR, said Thursday that DNR hydrologists still are poring over the Dec. 17 memo with the new flow data. It's still not certain if the short amount of data reflects the true, long-term average flow, Colvin noted.

"I doubt that it's a deal breaker at all,'' Colvin told the News Tribune of the new information. He said it's not yet clear what impact the flow data will have on the environmental review going forward "but it's something we'll have to look at and evaluate."

Colvin said it hasn't yet been determined if computer models need to be redone to reflect the new data.

"That's a judgment our technical experts will have to make,'' Colvin said.

The debate over "re-modeling," Colvin said, "is at the heart of the discussion we'll have between the draft and the final EIS (Environmental Impact Statement)" likely to occur sometime later this year.


But, he also said regulators may want see another year's worth of flow data before moving forward with new models, and it's not clear what impact that would have on the project moving forward.

Paula Maccabee, attorney for the group Water Legacy, who first obtained the DNR memo, said groundwater flows and stream flow appear to have been underestimated. The higher actual water flow rates "significantly affects how much pollution will seep from mine pits and mine wastes, the volume of water that would have to be treated, the potential for indirect effects on wetlands and even the potential need for stream augmentation at the Partridge River."

"All of the numbers and predictions they came up with for water flow at the mine site are wrong now,'' she said. "They really have to go back in and now and do the water modeling over."

The PolyMet project, what would be Minnesota's first copper mine, is in the midst of a public comment period on the so-called Supplemental Draft Environmental Impact Statement.

Colvin noted the actual flow measurements came in between the 0.5 CFS level predicted by PolyMet and the 3 to 5 CFS flows predicted by the tribal agencies. But critics counter that there was an ongoing drought during much of late 2011 and in 2012 when the flow was being measured, meaning the normal year flows could be even higher.

In a March 2012, letter to the DNR, John Coleman, hydrologist for the Great Lakes Indian Fish and Wildlife Commission, said that it's "unlikely that any accurate predictions of water movement, transport of contaminant mass, or contaminant levels can be made when the characterization of the hydrologic system is so out-of-kilter."

John Myers reports on the outdoors, natural resources and the environment for the Duluth News Tribune. You can reach him at
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