The Minnesota Department of Natural Resources on Wednesday clarified which numbers it used for water modeling that went into the environmental study on PolyMet's proposed copper-nickel mine.
The data in question were used to estimate the flow of the Partridge River, which is located near the mine site in northeastern Minnesota. Earlier this week, DNR officials said the department used a number three times lower than new data have shown.
But now officials said the data used in PolyMet's environmental impact statement is within the same range. The input value used in the model for the river's base flow was 1.5 cubic feet per second, and the new data provided a range of 1.3 to 1.8 cubic feet per second, officials said.
"We don't see a discrepancy here," said Steve Colvin, the DNR's deputy director for ecological and water resources.
Colvin said there was an earlier misunderstanding between hydrologists and those putting together the environmental impact statement over which numbers had been used.
"This is an incredibly complex model with thousands of assumptions and parameters," he said.
Colvin said hydrologists will continue to compare the different data sets to determine whether adjustments will be needed before a final EIS is issued. Officials will also evaluate other new data concerning other parameters to determine if they should be incorporated into the document, he said.
"We want to make sure whatever we'd use is the best data set," he said.
Critics of PolyMet's mine proposal have said there are problems with the environmental study, including inaccurate data. Besides new data the DNR has collected, it's possible officials will have to make other adjustments based on comments received on the environmental study.