Critics say the new rule could cause increased regulation for taconite iron ore processing operations and some municipal sewage treatment plants.

If the new rules are applied and enforced, critics say it could cost millions of dollars for the mining companies to comply, spurring mine shutdowns and layoffs.

The Iron Mining Association of Minnesota, which represents the state's mines and 150 companies that supply them, will be joined at a media event in Virginia on Thursday by the Range Association of Municipalities and Schools, the Iron Ore Alliance, United Steelworkers of America union leaders, local chambers of commerce, Jobs for Minnesotans, Better in our Back Yard and others opposed to the proposed wild rice sulfate standard that the groups say threatens the economic vitality of the region.

Several environmental groups also oppose the new rules — but that's because they say they don't go far enough to protect wild rice from industrial pollution.

Supporters of strong wild rice protection say the mines have long been given a free pass to release high levels of sulfate into local waters. It's that sulfate, when converted to sulfides in the sediment on the bottoms of lakes and rivers, that scientists say damages wild rice. High levels of sulfate and thus sulfides render some areas uninhabitable for the wild plant that's considered critical for wildlife and a key cultural food for the Ojibwe and other Minnesotans.

The Minnesota Pollution Control Agency in August announced a new wild rice sulfate standard, years in the works, developed after an old standard was deemed too difficult for industry to meet. A law in place since 1973 limited sulfate pollution in waters that hold wild rice to 10 parts per million. But the PCA said that rule was too broad — that some water could handle more and some waters less sulfate.

The new rules will instead study the water chemistry of each wild rice lake and river to determine what sulfate level they could handle and still grow wild rice. The new rule, if enacted, will limit sulfides to 120 micrograms per liter.

There are about 1,300 lakes and rivers listed so far on the statewide list of wild rice waters About 350 of those wild-rice waters are downstream of industries that discharge sulfate and are the most likely to be affected by the changes.

Hearings are scheduled for:

• Monday from 10 a.m. to 4 p.m. in the state's Harold E. Stassen Building, 600 N. Robert St. in St. Paul

• Tuesday from 4-9 p.m. in the Mesabi Range Community College Theater in Virginia

• Oct. 25 from 4-9 p.m. in the Beaux Arts Ballroom at Bemidji State University

• Oct. 26 from 3-7 p.m. in the Fond du Lac Community College Amphitheater, 2101 14th St. in Cloquet

• Oct. 30 from 4-9 p.m. in the Central Lakes Community College Cafeteria in Brainerd.

A statewide videoconference also is scheduled for Nov. 2.

Written comments on the wild rice sulfate plan will be accepted through Nov. 2 at minnesotaoah.granicusideas.com/discussions or mail to Office of Administrative Hearings, P.O. Box 64620, St. Paul, MN 55164-0620 (Docket 80-90030-34519).