Report outlines sulfate limits for wild rice

The Minnesota Pollution Control Agency on Wednesday released its preliminary findings on how much sulfate pollution is too much for wild rice, saying a two-year, $1.5 million field and laboratory study shows sulfate above 4-16 parts per million c...

The Minnesota Pollution Control Agency on Wednesday released its preliminary findings on how much sulfate pollution is too much for wild rice, saying a two-year, $1.5 million field and laboratory study shows sulfate above 4-16 parts per million can produce a chain reaction in the ecosystem that harms wild rice.

When sulfate levels are that high or higher in the water around the roots of wild rice plants, they can spur the production of hydrogen sulfide, and that hydrogen sulfide can starve the plant of nutrients.

The report said wild rice generally suffers when sulfide levels hit 150-350 parts per billion. Those levels began to occur when the surrounding water had sulfate starting at 4-16 parts per million, especially in waters with low iron concentrations.

The 22-page report said site-specific limits on sulfate may be needed where iron concentrations are low in the water.

But the PCA stopped short of deciding whether the current, controversial statewide standard of 10 parts per million for sulfate pollution in wild rice waters should continue, go up or go down.


John Linc Stine, PCA commissioner, said the agency simply doesn't have enough data to make that decision at this point. The analysis now will go to a scientific technical review panel. It may be late 2015 or early 2016 when the PCA issues a more definite finding on what changes to make, if any, to the state's current 10-parts-per-million limit for sulfate release into wild rice waters.

It could be 2017 before any new state regulation is adopted.

"We now know more about the relationship between sulfate and sulfides. But there are still a lot of unanswered questions. ... We just aren't there yet,'' Stine said.

But tribal and environmental groups say the science clearly shows the current standard is needed.

"They seem to not want to come out and say it in their analysis, but it's clear that there's nothing in the results to suggest changing the current sulfate criterion,'' said Nancy Schuldt, water project coordinator director for the Fond du Lac Band of Lake Superior Chippewa. "There's very high bar here to warrant any change in the current standard, and that bar certainly hasn't been met."

But business interests say the opposite, that the science shows sulfate is not a direct cause of harm and that no sulfate limit should be imposed. The Minnesota Chamber contends the limit should be 1,600 parts per million.

Tony Kwilas, director of environmental policy for the Chamber, said the PCA analysis lays out how the sulfate issue will move forward.

"It's going to get peer review now, and then it's going to the administrative rulemaking process and we will take part as that process moves forward,'' Kwilas said. "We appreciate the fact they're taking the time to get it right."


Ultimately, even after the PCA decides on the sulfate issue, the federal Environmental Protection Agency will have to sign off on any change under the federal Clean Water Act.

The sulfate standard for wild rice could have a major impact on northern Minnesota's mining industry, with several operations potentially in violation of the standard. But the standard, if enforced, also could have an impact on regional wastewater treatment plants, depending on where their discharge is released.

Still to come is perhaps an even more controversial decision by the PCA -- precisely which lakes and rivers in Minnesota are official "wild rice waters." The Minnesota Department of Natural Resources in 2008 compiled a list of 1,286 potential wild rice waters -- lakes, rivers and ponds -- with wild rice confirmed in 777 of them.

Some groups say that list should be greatly expanded for the official PCA definition. Others say it should be pared down. That decision, which the PCA says will come after an exhaustive administrative rulemaking process during the next year, will decide where the sulfate standard will be enforced.

If an industry or sewage plant is not on an official wild rice water, the sulfate standard won't be enforced.

The PCA also must better define when the standard applies -- all year or only during the growing season. The report released Wednesday seems to show that the sulfate-to-hydrogen sulfide conversion can occur at all times of year, although less often in colder conditions.

The PCA's analysis is based on the results of two years of field and laboratory work. The data was collected by studying wild rice in outdoor tubs and indoor labs at the University of Minnesota Duluth and by University of Minnesota Twin Cities campus scientists studying wild rice in rivers and lakes statewide.

The scientific work, while limited in time and scope, showed that sulfate at certain levels does indeed affect wild rice, as suspected. But it's not a direct, toxic effect, said John Pastor, the lead UMD scientist on the project. Only when the sulfate is converted to sulfide does it have an adverse impact on wild rice.


That conversion happens in the sediment as the plant tries to pick up nutrients, Pastor said, effectively starving the plant. Where sulfate wasn't converted to sulfide, wild rice generally wasn't damaged, he said. The laboratory work corroborated the field work, Pastor noted, as well as observations made in the 1940s.

Pastor said Wednesday that the PCA report provided the correct information regarding sulfate and sulfide levels. He said that the finding that sulfate levels between 4 and 16 parts per million fall within the 75th percentile of confidence means that a sulfate limit in that range would protect wild rice about 75 percent of the time.

"If you want higher confidence than 75 percent that wild rice would be protected, it means you'd have to have an even lower sulfate standard,'' Pastor said. "So, that means that the current standard stands, at least for now."

The sulfate rule, if enforced, has huge implications for the state's iron mining industry, with some taconite processing plants apparently releasing sulfate at levels above the current standard. It could affect the state's fledgling copper mining industry as well as wastewater treatment plants in areas where wild rice grows, or did grow in the past. The proposed PolyMet copper mine, for example, can meet the existing sulfate standard, an environmental review concludes, but only by treating water that leaves the site for decades, possibly centuries to come.

Environmental groups and tribal natural resource agencies counter that the current rule is based on an obvious impact and that sulfate pollution may be one reason many wild rice waters have seen wild rice crops greatly diminished in recent years. Long stretches of the St. Louis River, for example, are now devoid of the famous wild food source that's considered a sacred gift by many Ojibwe people.

Sulfates are ions or salts that can come from decaying plants and animals as well as some mineral deposits and industrial processes such as mine discharges, mine stockpiles and waste piles, tanneries, steel mills, pulp mills, sewage-treatment plants and textile plants.

The current sulfate rule was enacted in the 1970s based on work from the 1940s by a state biologist who found that wild rice didn't grow in water with high sulfate levels. The current standard of 10 parts per million was upheld in December 2012 by a state court of appeals ruling pending the study and PCA's review of the issue.

Minnesota lawmakers tried, on their own, to relax the state sulfate rule in 2011 in an effort to help industry. But the EPA said they could not change a law tied to the Clean Water Act without scientific backing. So the Legislature also approved money for what became the state's largest study of wild rice.


While the state-funded study is over, Pastor said his efforts have received a $200,000 SeaGrant grant and another $60,000 from the Fond du Lac Band of Ojibwe to continue his work over a longer period of time to see if the impact of sulfate to sulfide conversion changes over several more years, well beyond the two years in the state study.

John Myers reports on the outdoors, natural resources and the environment for the Duluth News Tribune. You can reach him at
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