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How an Iron Ore Mine Would Operate in Northern Wisconsin

Susan Bence

The GOP-backed mining bill would alter Wisconsin's permitting process for iron ore mining, to accommodate a huge iron-ore mine just south of Lake Superior.

Pushing aside the heated debate surrounding the issue, WUWM Environmental Reporter Susan Bence reports on how the proposed mine in the far off Penokee Range would operate. While several experts offer a rendering, unknowns remain.Bob Seitz is neither a Gogebic Taconite executive nor its engineer, but he has done his share of jumping into the mining debate. That’s his job as company lobbyist.

Seitz sketched a rudimentary picture of the project’s scope over the phone, when I reached him in his Madison office. He says the operation would cut down a section of the Penokee Ridge and then dig into a chunk of earth measuring approximately 4 miles long and 1.5 miles wide.

“The actually area of the excavation is under four miles. There would likely be an initial pit and then a secondary pit, then you fill in the first pit with the second pit,” Seitz says.

The first pit would require shallower digging than the second, deeper hole needed to reach the iron. Everything they remove beforehand, called the overburden, they would pile temporarily, on nearby land the company has leased from Iron County. Seitz says, when crews begin on a second pit, they would dump its overburden into the first hole. The company would eventually turn the second, deeper pit into a lake.

Seitz says Gogebic Taconite’s plan is to make the footprint as small as possible for the mine. He says restricting the footprint means piling the overburden as close to the mine as possible and processing the iron ore on site.

“At the plant the rock is ground down into a sand and put in water and run past the magnet. The magnet draws out the iron,” Seitz says.

The state estimates, for every ton of ore the plant processes into centimeter pellets and loads onto nearby rail cars, there would be three tons of waste. Seitz describes the leftover material as “sand.”

“An oxide, a silica, a sand basically; and that they would squeeze the water out of, so it could kind of packed into the landforms that are in the reclamation plan,” Seitz says.

Seitz says, before the company could sink a shovel into the ground, it must nail down a reclamation plan detailing how it would leave the site after extracting the iron. Eventually crews would take out the plant and the roads and everything that is involved in the mine.

Tom Fitz has closely followed the proposed mine from close proximity – he teaches geosciences at Northland College in nearby Ashland. He can fill in certain details. For example, Fitz says part of the project’s complexity has to do with the fact that the iron deposit sits at a 65-degree angle in the earth.

Fitz drew cross sections of the proposed mine site:


The iron ore would be extracted from the Ironwood Iron Formation. This formation, along with the Tyler Formation, contain an acid-runoff producing mineral - pyrite. (Note: The proportion of waste rock on the "Big-Mine" Cross Section is to scale, but it may not be stored as depicted.)

“The mine would start out at the surface and move downward and when it got to about 300 to 400 feet, then what would happen is it would have to start impinging on the formations above and below at which point the waste rock would increase,” Fitz says.

Fitz says the proposed mine would dip down to 1,000 feet over a projected 35-year lifespan. He says it’s hard to fathom how much material would be moved in the process, but the state estimates the quantity at 29 million tons a year. Fitz says even if crews put a sizeable amount back into the hole, its content must be carefully managed. Some of the waste rock removed and crushed - no one is yet certain how much, contains a mineral called pyrite, and Fitz says that illustrates one point of concern.

“It’s stable when it’s in the earth, when it’s brought to the earth’s surface and it’s in contact with water and oxygen and it weathers quite quickly and makes sulfuric acid which also puts other toxic metals into the solution,” Fitz says.

The Penokees are part of a 700,000 acre watershed. It feeds into with Lake Superior.

Bob Seitz says Gogebic Taconite is confident it can properly manage its waste and besides, state and federal agencies will be looking over its shoulder.

"There are overlapping overlaying regulations just in the DNR regulations, but then you overlay on those the Army Corps of Engineers, potentially the EPA, it is incredibly regulated," Seitz says.

His confidence may not ease the minds of skeptics.

They may have further doubts, now that Illinois’ environmental agency is pursuing the same investor, for failing to clean groundwater pollution at a coal mine in that state.