Three years after the Legislature ordered a study on how a key pollutant affects wild rice, state officials said more questions remain about whether and how Minnesota water quality standards should change.
The standard affects discharges by mining operations, other industrial facilities and wastewater treatment plants into wild rice-producing waters, and the review has been closely watched by Indian tribes, mining companies and environmental groups.
The study aimed to confirm a relationship between the growth of wild rice and the presence of sulfate in lakes and rivers. The research did confirm a relationship, but it's a complex one, raising questions about whether the state's current 10 mg/L sulfate limit for waters where wild rice is grown should be the catchall standard.
The research shows sulfate is not directly toxic to wild rice, but it can be converted into sulfide, which is toxic. The Minnesota Pollution Control Agency said that fact is leading officials to consider whether the state needs a sulfide standard to protect wild rice either instead of, or in addition to, the sulfate standard.
The research also found instances where higher levels of sulfate in waters did not translate into high levels of the toxic sulfide. The MPCA said that finding could mean the state needs site-specific standards given the complex biology and chemical interactions of different waterways.
"I'm not ready to say whether [the research] supports a change in the standard or not. I think what it suggests is we need to keep working with the data and the science to determine what will be protective of rice," MPCA Commissioner John Linc Stine said Wednesday. "There may be situations in which the current standard is useful, there might be other situations that we know there are site-specific conditions that lead us to think otherwise."
Stine said the agency will have a scientific review panel evaluate the research first before officials make recommendations on what to do with the state's sulfate standard. Those recommendations aren't expected until the end of the year, Stine said.
"You don't want to rush to get an answer," he said. "When you see the science is leading to a rich discussion, that's where I'd like to go...get the scientists to work on answering those questions."
Stine said he thinks the state will need a sulfide standard, and one of the tribes following the issue agreed.
"It's long been known that sulfide is extremely toxic to just about every living thing, not just wild rice," said Nancy Schuldt, water resource policy director for the Fond du Lac Band of Lake Superior Chippewa. Officials with the Minnesota Chamber of Commerce, who pushed for the study three years ago because of concerns the standard was too stringent, said they're happy the MPCA isn't making any conclusions yet.
"We agree with them that further scientific inquiry and analysis is needed," said Tony Kwilas, the Chamber's environmental policy director. "We thank them for the thoughtful and deliberative process that they've undertaken up to this point. You can't answer all of it today."
Kwilas said his group is looking forward to participating in the rulemaking process for the standards.
"This has statewide implications and we want to make sure we get it right," he said.
Meanwhile, the PCA has a parallel project under way to identify what exactly constitutes a wild rice-producing body of water, a crucial step, because that determines where the standard would be enforced.
A 2008 Department of Natural Resources report identifies over 1,200 bodies of water where wild rice grows. But historically the grain grew across much of the state. Regulators will have to determine if the standard should apply not only where the plant grows now, but also where it used to sprout.
A 40-year-old standard
The state's current standard was adopted in 1973 and affects mining operations, other industrial facilities and wastewater treatment plants that discharge into wild rice producing waters. The 10 mg/L limit is based on research conducted by John Moyle, a biologist for the Minnesota Department of Conservation in the 1930s and 1940s, who found that no large wild rice stands grew in waters high in sulfate. "The question is, can you go above that, and still be safe in protecting wild rice? How protective do you want to be?" said University of Minnesota-Duluth biologist John Pastor.
Scientists have long suspected that it's not actually sulfate that damages wild rice. In an oxygen-starved environment like the muck in wild rice lakes, they say, bacteria can essentially breathe in sulfate and exhale hydrogen sulfide, which can be toxic to wild rice and other aquatic life.
The new research confirmed that theory, said Pastor, who ran part of the study.
"The issue here is that the standard is a standard about sulfate," he explained, "but it's really what sulfate gets converted into that appears to inhibit wild rice growth."
And how efficiently sulfate is converted to sulfide, Pastor said, depends on the kind of aquatic environment where it's discharged. For example, in well aerated, gravel-bottomed rivers, very high sulfate levels wouldn't result in much sulfide. But in mucky, slow moving lakes, he said, it wouldn't take much sulfate to result in a level of sulfide harmful to wild rice.
That could lead to different recommended standards for lakes and rivers. But, as Pastor points out, rivers often flow into lakes. "So you can set a higher sulfate standard in a river, and things might be fine, but if that river flows into a lake, or you get into low flow channels in the river," a higher sulfate standard that protected wild rice upstream might not be sufficient further downstream, he said.
The scientific expert review panel will meet this summer, and the agency will also receive public input before finalizing its recommendations.
If regulators decide to change the existing standard, a rulemaking process would likely begin next year. Any changes would have to be approved by the EPA.
The MPCA had originally planned to release its policy recommendations for sulfate now, but Stine said officials decided they weren't ready.
"We had a lot of questions we couldn't settle in our own mind, so we thought it was better to put the info out there in such a way that everyone could see what we're seeing, and struggle with the same questions together," he said. "There are a lot of different folks who care about this."
Your support matters.
You make MPR News possible. Individual donations are behind the clarity in coverage from our reporters across the state, stories that connect us, and conversations that provide perspectives. Help ensure MPR remains a resource that brings Minnesotans together.