The Minnesota Pollution Control Agency on Tuesday released a more detailed, amended version of its plan to set sulfate limits for each lake and river where wild rice grows.
The changes come more than a year after the PCA first announced its plan to switch from a single, statewide sulfate limit of 10 parts per million for wild-rice waters to a system that will take into account the water chemistry of each lake and river.
The changes announced Tuesday are technical but continue the agency down the path toward developing a new sulfate rule by January 2018, said Shannon Lotthammer, director of the PCA's environmental analysis and outcomes division.
That rule would see the PCA develop a standard for each of 1,300 or more wild-rice lakes and streams using a complicated equation that measures iron, carbon and sulfate in the water to see where and how much toxic sulfide develops that can kill wild rice.
The PCA says the science seems to show that the amount of sulfide in the water is determined by that mix of iron, carbon and sulfate - with excess sulfate that's triggering the toxicity in some cases coming from human-caused sources such as taconite iron ore processing and wastewater treatment plants.
Among the changes, now open for expert feedback into September, the PCA says it has lowered the amount of sulfide in water; sulfide is deemed to be toxic to wild rice by inhibiting nutrient uptake through roots. The agency last year had proposed 160 parts per billion of sulfide as the danger threshold but has now reduced that to 120 parts per billion.
It's believed that sulfate pollution in lakes, depending on natural iron and carbon levels, increases sulfide which in turn starves the wild rice. The PCA has said higher iron levels may help reduce the sulfate to sulfide conversion and thus allow higher sulfate pollution levels with no impact on wild rice.
The agency also has refined how it will allow new lakes and rivers to be added to the wild-rice list in the future, in addition to the roughly 1,300 waterways that would be included in the first version. To make the list, there would have to be proof of historic wild-rice harvesting on the lake or river since 1975 - when the federal Clean Water Act took effect on state pollution limits - or there would have to be at least eight stems per square meter of rice across at least a quarter-acre of water. That replaces an 8,000-stem requirement per waterway proposed last year.
Any sulfate limits developed would only apply to waters that fit those definitions. And the sulfate limits would only apply to industries that received state permits to discharge pollution.
"We're continuing down the process of rulemaking,'' Lotthammer said Tuesday. "We're definitely following the science."
The state has had a sulfate pollution limit of 10 parts per million since the 1970s with little or no enforcement and little attention until about 2010. But environmental and tribal groups began to push enforcement of the limit as a way to restore health to diminished wild-rice beds in northern Minnesota.
As efforts to enforce the sulfate limit increased, however, many mining and industry groups said the old limit would stifle or even shut down some businesses. Some taconite and sewage plant discharges are much higher than 10 parts per million. In 2010, the Minnesota Chamber of Commerce, on behalf of five taconite plants, sued the state, saying the 10 parts per million standard was arbitrary and illegal. The current standard of 10 parts per million was upheld in 2012 by a state court of appeals ruling pending the study and PCA's review of the issue.
The 2011 Minnesota Legislature ordered the PCA to revisit the issue, and Iron Range lawmakers have been leaning on the state agency to change the limit for fear enforcement will stifle mining and jobs.
Under those pressures, early in 2015 the PCA said it would abandon a single, statewide sulfate limit for wild-rice waters and move to the lake-specific limit, noting that for about two thirds of all wild-rice waters the 10 parts per million limit is either higher or lower than it needs to be to protect wild rice.
Paula Maccabee, attorney for the environmental group WaterLegacy, said the PCA appears to be ignoring new research that shows iron may not play any beneficial role in reducing the impact of sulfate. That research, by Prof. John Pastor at the University of Minnesota Duluth and funded by Sea Grant, concluded there is no buffering impact by iron on the sulfate/sulfide conversion.
"We already know that the existing sulfate limit is effective and reasonable. But PCA, ignoring evidence that the equation they are developing is flawed, continues down this path and away from protecting wild rice," Maccabee said. "They are developing this very complex and flawed process based on pressure from the mining industry and Iron Range lawmakers when their primary concern should be protecting wild rice."
Maccabee has said the Environmental Protection Agency, which is already investigating the PCA on allegations the agency has failed to uphold water pollution permit requirements, may frown on the revised sulfate standard as well. As reported in the News Tribune in March the EPA is combing over records to see if the PCA has upheld Clean Water Act rules when issuing permits, some of which have been expired for years. The EPA also is looking at how and why the sulfate limit became subject to change.
The end result could be a federal takeover of all Minnesota water pollution discharge permits.