DNR now claims water flow discrepancy not serious
But agency press statement called “misleading” by tribal environmental expert
Marshall Helmberger

REGIONAL—The Minnesota Department of Natural Resources has suggested in a press statement issued Jan. 28 that a major discrepancy in the PolyMet draft supplemental environmental impact statement, or SDEIS, previously acknowledged by agency officials, may not be a discrepancy after all. But tribal officials and others who have been critical of the SDEIS, say the DNR’s claim is misleading, and that the discrepancy remains unresolved.

At issue is the amount of water that flows through the area affected by the proposed mine, which sits near the headwaters of the Partridge River, a tributary of the St. Louis River. In determining the mine’s effects on water quality, the “base flow” rate for the river is a key variable, but it’s one for which agencies like the Department of Natural Resources do not have reliable data. The base flow number is important as a measure of groundwater flow through the system, which could help determine how quickly contaminants from the mine might be released into the environment.

Last month, DNR officials had acknowledged that the base flow estimate used in a water quality model for the SDEIS had underestimated the actual groundwater flow by a factor of three— an acknowledgement that garnered statewide headlines after the story was first broken by the Timberjay. According to DNR officials at the time, the model had used a base flow number of 0.5 cubic feet per second, or cfs, while more recent data suggested that actual base flow was between 1.3 and 1.8 cfs. While hydrologists were unclear on the effect of the discrepancy, critics of the project quickly pounced on the issue and called for new model runs to clear up any discrepancies.

The apparent error was a potential embarrassment to lead agencies on the SDEIS, which include the DNR, along with the U.S. Army Corps of Engineers and the U.S. Forest Service, and could well have delayed completion of the final SDEIS, potentially by several months, if officials had determined that a new model run was necessary.

But in the DNR’s Jan. 28 statement, the agency claimed that the model had included an additional 1.0 cfs to account for surface water discharge into the Partridge River from the Northshore taconite pit, located just north of the proposed PolyMet mine. The agency stated that adding in that additional flow put the actual base flow number at 1.5 cfs, which they said closely approximated the more recent data.

But John Coleman, Environmental Section Leader for the Great Lakes Indian Fish and Wildlife Commission, said the DNR’s explanation gets it wrong, even though the agency’s technical staff likely knows better. “I’m really disappointed that they are putting out this kind of misinformation,” he said. “I was afraid that the DNR would try to come up with some excuse. I’m hoping that they’ll back off from this.”

Coleman acknowledges that the model does add 1.0 cfs to the Partridge River flow calculation, but he said that’s an entirely different issue. He said the base flow number is used to determine groundwater movement, and that when calculating the figure, hydrologists work to exclude any flow from surface runoff or other sources. “This is an excellent example of comparing apples to oranges,” said Coleman, who was one of the first researchers to alert the DNR to the base flow discrepancy within the model. Indeed, Coleman raised the issue as early as 2008, but tribal officials say their concerns were initially discounted, until new data showed their concerns were well-founded.

At this point, it remains to be seen how the study’s lead agencies will respond. Steve Colvin, the DNR’s point person on the SDEIS, said the agency’s hydrologists are still studying the issue, and have made no decision on whether new model runs will be necessary.

The issue is certain to be a major focus of comments from both tribal experts, who serve as cooperators in the SDEIS, as well as hydrologists hired by some environmental groups to analyze the study.

The volume of those comments could push back completion of the SDEIS for many months in either case, which could allow the lead agencies time to refine their modeling.

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1 comment on this item

Thanks for identifying the flow rate range. I had imagined the flow was much larger. This difference may seem significant, but not to me. 1 or 2 cubic feet per second are very low flows. Either would fit through a driveway culvert!

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