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Appendix C: ORD Specific Conductance Memo, from Susan Cormier to Tera Fong. March 15, 2022. Assessment of effects of increased ion concentrations in the St. Louis River Watershed with special attention to potential mining influence and the jurisdiction of the Fond du Lac Band of Lake Superior Chippewa
Citation:
Cormier, S. AND Y. Wang. Appendix C: ORD Specific Conductance Memo, from Susan Cormier to Tera Fong. March 15, 2022. Assessment of effects of increased ion concentrations in the St. Louis River Watershed with special attention to potential mining influence and the jurisdiction of the Fond du Lac Band of Lake Superior Chippewa. U.S. Environmental Protection Agency, Washington, DC, 2022.
Impact/Purpose:
1) Region V has requested a information to evaluate potential effects from a proposed mine in Minnesota in the headwaters of the St. Louis River, MN that may cause or contribute to water quality violation of Fond du Lac Reservation water quality standards for specific conductivity, (SC) a measure of dissolved charged ions. 2) Ionic composition and less disturbed background SC was characterized at different spatial scales. Implications for lake sturgeon, brook trout, and aquatic benthic invertebrates were evaluated based on the literature and analyses of taxon occurrences and SC. 3) Region V will consider this memo in deliberations about the proposed mine. 4) Although intended for EPA Region V, Office of Water , the Army Corps of Engineers , the Fond du Lac Band of the Chippewa, the Minnesota Pollution Control Agency may also consult this memo. The mining community has a vested interested in development of the mine.
Description:
PolyMet Mining Corporation, Vancouver, Canada has proposed an open pit mine to extract copper, nickle, and other metals. The proposed site is located in the Superior National Forest between Babbitt and Hoyt Lakes, Minnesota in the Northern Lakes and Forests Level III Ecoregion 50 (Omernik, 1987). EPA Region 5 is considering whether they should recommend additional conditions (e.g., BMPs, monitoring/benchmarks, mitigation techniques) that would minimize the potential for water quality (WQ) violations on the Fond du Lac Reservation including those for total ions measured as specific conductivity (SC). EPA ORD is providing, for EPA Region 5's use, estimates of background SC, stream SC levels, and benchmark SC levels for biological effects. The results of analyses provided by ORD relate to an assessment area of the proposed mine site and downstream via the St. Louis River to Duluth, MN including reservation lands of the Fond du Lac Band of Lake Superior Chippewa. The assessment characterizes ionic composition in stream water and effluent from the current mine site, least disturbed background SC, effects for lake sturgeon, brook trout, and benthic invertebrates. The assessment finds that SC levels from mine waste at the proposed mine site exceeds levels know to extirpate both fish and benthic invertebrate taxa. Furthermore, cumulative inputs from the Mesabi range and other sources contribute dissolved ion loadings that maintain or intermittently exceed benchmarks shown to cause extirpation and reduce the probability of observing fish and benthic invertebrates within the Fond du Lac Reservation jurisdiction.
URLs/Downloads:
APPENDIX C ORD SPECIFIC CONDUCTANCE MEMO.PDF (PDF, NA pp, 4692.961 KB, about PDF)https://www.epa.gov/mn/polymet-northmet-mine#materials