The debate over sulfide mining

Richard Patelke
Richard Patelke examines a small length of stone from a core sample, drilled from rock where PolyMet expects to uncover copper, nickel, and precious metals. Patelke is a geologist with PolyMet Mining Corp.
MPR Photo/Bob Kelleher

It's chilly, musty, and dimly lit in the old shop building at the former LTV Steel Co. taconite plant near Hoyt Lakes. Cardboard boxes are lined up, side by side, in order, on a counter. Inside are rocks -- half-circle samples from a core drilled deep into the earth nearby.

PolyMet processing site
PolyMet Corp. has purchased key processing equipment once used to process taconite by LTV Steel. The large building in the foreground is the crushing facility, where ore will be ground before metals can be extracted.
Photo courtesy PolyMet Corporation

Geologist Richard Patelke holds a few of the rock chunks. These came from close to the surface.

"The remarkable thing about this part is it's so unremarkable." Patelke says. "Piece after piece of this looks the same."

It's maybe halfway down the table, toward the wall, when Patelke points to something different.

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"You come to this, and you're out of this waste rock and you're in to sulfide bearing material," says Patelke.

Sulfide bearing materials -- an unremarkable term for the kind of rock that might hold copper and nickel, even precious metals like platinum, palladium and gold. It's the minerals found with sulfides they're after at PolyMet Mining Corporation. PolyMet is planning a new mine near Hoyt Lakes using new processes to recover the metals.

Tammen, left;  Hanson, right
Clyde Hanson, right, is with the Sierra Club Northstar Chapter. He follows environmental issues from his home near the North Shore of Lake Superior. Bob Tammen, left, is a Sierra Club member who lives in Soudan, on the Iron Range.
MPR Photo/Bob Kelleher

But environmentalists are not happy. The term sulfide mining is a lightning rod.

On a recent spring day, Minnesota's mining experts met in the Duluth convention center. The Sierra Club's Clyde Hanson used the occasion to draw attention to his concerns about PolyMet's new mining venture.

The problem with sulfur is how easily it produces sulfuric acid when it contacts air. Hanson says rainwater can wash the acid and metals like copper and nickel out of rock piles, and from the walls of mine pits.

"The acid changes the chemistry of lakes and waters and streams ... kills fish and wildlife, kills the critters at the bottom of the food chain," Hanson says. "It lasts. It's a persistent pollution. It just keeps oozing out these sulfur wastes for generations of time. So it creates a situation where you might have to collect all this waste and run a treatment plant forever."

Hanson says it doesn't take much to cause big problems. Hanson says the damage begins when mining begins.

A lot of us, we live in this country, we don't want to crap in our own nest. That's really what it amounts to.

"I mean 99 percent of the damage is done just by uncovering the ore body and removing the waste rock on top," says Hanson. "So the first day the mine produces ore, 99 percent of the environmental damage already had been done."

There have been some spectacular disasters.

The Summitville gold mine in southwestern Colorado is perhaps the poster child of destructive mining. A U.S. Geological Survey report says problems began there soon after open-pit mining for gold began in the 1980s.

Cyanide, used to release the minerals, leaked into waste piles, leaching metals and acids that poured into the Alamosa River.

The mining company went bankrupt, and the federal government stepped in for an emergency and very expensive cleanup. A dozen other western mines have legacies not much better.

The Sierra Club's Bob Tammen lives north of the proposed Minnesota mine. He doesn't want to see that in Minnesota, not even for hundreds of new jobs.

Don Hunter
PolyMet Project Manager Don Hunter stands before a taconite tailings pit abandoned by LTV Steel mining company. Under PolyMet's plans, the pit will hold tailings from PolyMet's copper/nickel and PGM group metals mining.
MPR Photo/Bob Kelleher

"A lot of us, we live in this country, we don't want to crap in our own nest," Tammen says. "That's really what it amounts to."

State and federal regulators are now preparing an Environmental Impact Statement for the PolyMet mine. The company is testing how much acid much might leach from the mine's waste rock. But that doesn't satisfy Clyde Hanson.

"PolyMet's proposing to open the mine before all the scientific testing is done on the pollutants that would come off this kind of waste rock," Hanson says.

Hanson says that violates state law on sulfide mining created 15 years ago.

"The law is quite straightforward," says Hanson. "It says you have to finish the science before you can make a decision on whether you can issue the permit to mine. And it takes years to do this kind of science."

Maybe the law isn't that straightforward.

Arlo Knoll, with the DNR's Division of Mining in Hibbing, says the rules require tests, but don't spell out a timetable for the testing.

Proposed PolyMet site
A graphic illustrating the proposed PolyMet mining pit.
Image courtesy of PolyMet

They're the kind of tests that could take years, according to PolyMet Project Manager Don Hunter. In the meantime, Hunter says precautions will be taken to ensure there's no problem with sulfuric discharges.

"We're not about to do stuff that is illegal, or we're not trying to fast-track or circumvent anything," Hunter says. "We're doing it absolutely according to the rule book. And we're working very very close with the regulators -- the DNR, the PCA, the Corps of Engineers -- to make sure that everything we do goes through them, that they are happy with what we're doing, and that it complies with the rules and legislation."

Meanwhile, he says, fears about acid are overblown. PolyMet's ore body is spread thin through the rock. That's one of the reasons it's never been mined. Hunter says the ore's sulfur concentration averages around 0.6 percent. Compare that to a 30 percent sulfur concentration at the 1990s Flambeau mine in Wisconsin.

Waste rock considered acidic would be encapsulated in liners, according to PolyMet Assistant Project Manager Jim Scott.

"They'll be designed to keep water and air away from the waste," Scott says. "And if there's no water and no air, there can't be a reaction. They'll be on a liner, so that any of the water that does find its way through the stockpile is collected and routed to a central location, and if it requires treatment then it will be run through a treatment plant."

Downtown Hoyt Lakes
The sign near downtown Hoyt Lakes points to the LTV Steel taconite plant, which closed five years ago.
MPR Photo/Bob Kelleher

PolyMet intends to avoid perhaps the most destructive parts of metal mining. There will be no poisonous solvents like cyanide, and no smelter to cook the ore. Smelting can create serious air pollution.

Instead, PolyMet will separate metals from ore in an autoclave -- a closed process using high heat and pressure. PolyMet officials say the only emission will be steam, which can be scrubbed for traces of acid.

PolyMet's Don Hunter adds that the state has a big hammer to ensure the mine is run cleanly and kept clean when it's closed in 20 or more years. The company will post a bond, large enough to cover the costs of restoring the entire mining and processing site.

"And that bond amount, which will cover not only the ongoing operation, the immediate post-closure actions, but also, if necessary, treatment in perpetuity, is going to be tens of millions of dollars," Hunter says.

Hunter stands in a grassy field. Behind him the ghostly, silent silhouette of LTV Steel's old taconite pellet plant. In front of him is a grassy depression, an attractive area that might become home to ducks as it collects water and becomes wetland. It's a restored taconite mining tailings pit, covered over and replanted.

Hunter says the entire PolyMet site will look as nice when it's closed. And he talks about the frustration of trying to open a new mining process. He says the project has been associated with a kind of mining that's not going to happen in Minnesota.

"We obviously will have an impact on the environment," Hunter says. "Everything we do as human beings impacts the environment in some way or another. But what we're planning to do is operate in an environmentally responsible manner, and then finally restore the site to a form that can be reused."

Regulators are in the early phases of studying the PolyMet proposal. A final Environmental Impact Statement is expected by June 2007. Construction could begin soon after, with production in early 2009.

A second metals mine is still in the planning stages. The Birch Lake Project would sink an underground mine under Birch Lake near Babbitt. That project could be producing metals in 2010.