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Minnesota revises proposed standards to protect wild rice from sulfate pollution

The refinements announced on Tuesday include a new definition of a “wild rice water” and adjustments to an equation that determines a “protective sulfate concentration.”

The state took another step Tuesday in a seven-year process to revisit a rule designed to protect wild rice from sulfate pollution, which comes from certain industries, notably taconite mines, and wastewater treatment plants. The Minnesota Pollution Control Agency has been tweaking a formula it designed last fall that tries to take into account the water chemistry of different lakes and rivers, resulting in different sulfate limits for different water bodies.

It’s a relatively new approach to pollution control. Shannon Lotthammer, director of the MPCA’s Environmental Analysis and Outcomes Division, said it can provide more effective protection than a fixed standard does.

The mining industry has challenged the state’s existing limit of 10 milligrams of sulfate per liter of water in wild rice waters since the MPCA began trying to enforce it about five years ago (the law has been on the books since the early 1970s).

“One of the challenges around the fixed standard is that folks would routinely point to water bodies with wild rice that had higher sulfate levels than 10, and they’d question the legitimacy of 10,” said Lotthammer. “This formula-based approach helps explain how that can be true, and also how there can be water bodies where 10 is not nearly protective enough, because they’re more sensitive.”

Converts to sulfide

Complications arise because sulfate does not harm wild rice plants directly, but bacteria in the sediment convert it to sulfide, which is poisonous to young wild rice seedlings. The agency’s research has shown that water with high levels of iron has less sulfide and water with high levels of organic carbon has more. Iron appears to react with the sulfide, forming a compound that agency officials say may protect the growing rice. So they created an equation designed to show how those two components would affect the conversion of sulfate to sulfide in any given water body.

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The agency’s plan for setting a standard for each wild rice water is to take 25 sediment samples, analyze them for the key components, and plug those numbers into the equation. The result would identify a “protective sulfate concentration.” Lotthammer said the equation provides a more accurate level of protection than the fixed formula, because it takes into account the role that carbon and iron play in controlling sulfate concentration. 

The refinements to the MPCA’s plan announced on Tuesday include a new definition of a “wild rice water,” adjustments to the equation, and other changes; they are detailed here.

University of Minnesota Duluth researcher John Pastor said the plan is better than it was when the agency first presented it last fall, but it’s still not ready for prime time.

Pastor’s results

Pastor has been studying the effects of sulfide on wild rice in controlled experiments for five years. Two years ago he added iron to the mix, and he has seen no protective effect from the iron. Pastor said the iron does indeed react with the sulfide, but together they form a black plaque that coats the roots of wild rice plants late in the growing season, possibly impairing the plants’ ability to draw in the extra nutrients they need to produce seeds for next year. In effect, the iron does remove the sulfide from the water, but it attaches it to the plants’ roots, where it apparently strangles the plants.

“While we cannot yet conclude from this experiment that iron has a strong depressive effect on wild rice growth via FeS (iron sulfide) plaques on roots, we can conclude that iron has no beneficial effect by reducing the toxicity of sulfide,” he wrote in his report to the research funder, Minnesota Sea Grant.

“This is typical in scientific research,” said Pastor. “You get one set of data that says one thing, and you have another set of data that says something else, so the purpose of research is to try and see if you can reconcile these two things somehow. Right now we’re in that middle phase of that process, so I just think it’s premature to jump ahead and start making sulfate standards based on the amount of iron when we’re not quite sure what this iron is doing.”

The MPCA is taking public comment on its revised plan until Sept. 6. It has consulted with tribal representatives and state legislators, and will hear from an advisory group in August. The agency will likely make further refinements, and then start a formal rulemaking process early next year. The legislature set a deadline of January 2018 to determine whether the standard needs to be changed.

Pastor’s research, and that of other scientists, is expected to be published in academic journals over the next several months.

The EPA investigation

The MPCA’s failure to enforce the sulfate standard is a key part of the federal Environmental Protection Agency’s investigation into whether Minnesota should be allowed to continue to issue water quality permits. Water Legacy, an environmental group, asked the federal government for the investigation, saying “Mining industry influence over Minnesota officials is pervasive and undermines the ability of the state to act in conformity with Clean Water Act pollution control requirements.” 

The EPA is waiting for Minnesota’s attorney general to explain whether the MPCA still has authority to implement its rules, given legislation from 2015 and 2016 that directs the agency not to enforce the sulfate standard. EPA said those laws “may constitute grounds for EPA’s determination that the MPCA’s legal authority no longer meets the requirements of a federally approved program.”

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Meanwhile, MPCA Commissioner John Linc Stine has put most of the agency’s mining permitting work “on pause” to concentrate on the sulfate standard review.