A Ramsey Court judge has upheld the state's standard for sulfate in waters that produce wild rice.
The Minnesota Chamber of Commerce challenged the rule, saying it was vague and arbitrarily applied.
The Minnesota Pollution Control Agency's Shannon Lotthammer said the agency is pleased that the court has affirmed the agency's use of the rule.
The MPCA recently gave U.S. Steel eight years to figure out how to reduce its sulfate concentrations.
"We do have a number of facilities that we don't have data for yet, so we don't know how much sulfate is in their discharge," said Lotthammer, who manages the agency's water assessment and environmental information section. "In that case, we're requiring those facilities to collect that data so the next time the permit comes up for reissuance we'll be able to use that information to determine if a limit is needed."
Concentrated sulfates from mines and other industrial operations can damage wild rice beds.
The sulfate concentration in wastewater at U.S. Steel's Minntac plant is about one-thousand parts per million; the state standard is 10 parts per million.