MPCA releases its proposal for protecting wild rice from excess sulfide

Contact: Cathy Rofshus, 507-383-5949

After years of research, data analysis, and consultation with tribes, and dozens of meetings and many hundreds of comments from stakeholders and concerned citizens, the Minnesota Pollution Control Agency (MPCA) has released its proposed changes to Minnesota rules that are meant to protect wild rice from certain types of pollution.

Wild rice is an important natural resource in Minnesota. It’s a cultural and spiritual resource to the Dakota and Ojibwe people and provides food for both humans and waterfowl. In 1973, Minnesota instituted a water quality standard to protect wild rice from elevated levels of sulfate, based on observations that wild rice grew in waters with lower sulfate levels, and didn’t in waters with elevated sulfate.

“We believe the changes we’re proposing are an innovative and precise approach to protecting wild rice,” says MPCA Commissioner John Linc Stine. “The proposal also allows for flexibility in permitting for facilities that discharge to wild rice waters.”

Cutting-edge research leads to innovative rule proposal

Today, the MPCA is proposing rule changes that take into account the newest evidence about how sulfate and sulfide affect wild rice. Peer-reviewed agency research begun in 2011 found that:

  • Sulfate in wild rice waters enters the sediment in which wild rice is rooted, and bacteria convert it into sulfide.
  • Higher levels of sulfide in the sediment create an environment that reduces wild rice growth and survival over time.

The existing rule (or standard) limits sulfate to 10 milligrams per liter in water used for the production of wild rice. However, the MPCA’s new research indicates that sulfide in the sediment in which wild rice grows is the pollutant of concern. The proposed rules are designed to limit sulfide to 120 micrograms per liter.

The sediment sulfide originates from sulfate in the water, but certain factors change the rate at which sulfate is converted to sulfide in the sediment. Most significantly, higher levels of iron in the sediment can lead to less sulfide, and higher levels of organic carbon can lead to more sulfide. So while sulfate may create conditions that negatively affect wild rice, no single level of sulfate can be protective of wild rice in all bodies of water.

The rule proposal sets up a process to identify the level of sulfate that is protective for each wild rice water: The MPCA will collect sediment samples in wild rice stands and measure iron and organic carbon concentrations, and then enter the data into an equation to determine the numeric sulfate standard for that wild rice water. The agency will use the wild rice rules to evaluate facilities that discharge to wild rice waters, such as wastewater treatment plants, mines, and industrial facilities, and, over time, determine if they need additional permit limits to protect wild rice.

The proposed rules also:

  • Identify the lakes, rivers, and streams to which the standard applies, termed “wild rice waters”
  • Set out procedures for collecting and analyzing sediment to determine carbon and iron levels
  • Address some issues around implementing the standard, particularly at facilities with water discharge permits

Public comment period now open

The MPCA is soliciting public comments on the proposed rules now. Public hearings on the rule proposal are scheduled at locations around the state between October 23 and November 2. Comments will be accepted until at least five days after the last public hearing. (The final comment deadline is determined by the hearing judge.)

To view all rule-related information, including the list of wild rice waters, the draft rule language, and the supporting Statement of Need and Reasonableness and Technical Support documents, visit:

Comments must be submitted to the Office of Administrative Hearings via the web (, by mail (Office of Administrative Hearings, P.O. Box 64620, St. Paul, MN 55164), or in person (600 N Robert St., St. Paul, MN). In your comments, you must include your name and address and identify the portion of the proposed rules you are commenting on, your support of or objection to it, and any change you are proposing.