The Minnesota Pollution Control Agency (MPCA) is proposing a framework for developing and evaluating site-specific standards for sulfate water concentrations. High concentrations of these sulfur compounds are biologically deleterious. In some parts of Minnesota mining activities can produce elevated sulfate concentrations that hurt beneficial water uses, most notably the growth of wild rice.
Federal water quality standards in place since 1973 protect the ecologically and culturally significant wild rice plants by limiting all wild rice growing waters to a sulfate concentration of no more than 10 milligrams per liter. The MPCA study will consider adopting an approach that allows for site specific standards that may be more or less stringent than the current 10 mg standard.
You can read the agency’s full document here.