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There are issues with Minnesota’s abandoned mines; the possibility of a toxic spill isn’t one of them

Why an environmental catastrophe like that caused by Colorado’s Gold King Mine is unlikely to happen at one of Minnesota’s many abandoned mines. 

Yellow mine waste water from the Gold King Mine is seen in San Juan County, Colorado, earlier this month.

Federal environmental officials knew they were dealing in dangerous territory. The abandoned Gold King mine in Colorado had spent much of the 20th century filling up with melted snow and rainwater that, combined with the mine’s tailings, had turned into an acidic toxic stew.

Over the years, various officials in the region tried to clean up Gold King. Most recently, it was the Environmental Protection Agency. On Aug. 5, while investigating a leak from the mine, a team contracted by the agency inadvertently shook loose debris that had been acting as a dam holding back the pollutants. Mustard yellow toxins poured into the Animas River.

The incident brought into question the future, and potential danger, of thousands of abandoned mines across the nation, including those in Minnesota, a state with a long history with mining. The North Star state is home to more than 100 abandoned mines dotting the Iron Range, and some are still being monitored by state officials as potentially harmful to the environment. 

Still, there are a number of reasons an environmental catastrophe like what happened in Colorado is unlikely to happen in Minnesota. Here’s why:

Iron rush v. gold rush

As in Colorado, Minnesota’s earliest miners were looking for gold, and in the 1850s, a lucky explorer discovered the precious metal embedded in some quartz near Lake Vermilion. The difference is that miners in Minnesota didn’t find much gold after that. What they found instead became far more precious to the region, though — iron ore, in huge quantities. 

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The industry formed the backbone of the area’s economy for a century: By the 1950s, 82 percent of iron ore extracted from American mines originated in Minnesota.  As mines were excavated past the point of usefulness and iron ore resources dried up, mines were simply left behind.

There was no agency regulating mining and its impact on the natural world for much of the industry’s history in Minnesota. But in 1969, state lawmakers recognized the impacts mining has on the environment, and the Legislature passed the first “reclamation” laws regulating safety and environmental concerns at old mining sites.

Lawmakers expanded on that law in 1977, giving the Iron Range Rehabilitation and Resources Board (commonly called the “I triple-R B”) tax funds and authority to manage all mines operated before 1980. All mines built or operated since then are under the management of the Department of Natural Resources (which handles permitting for new mine projects) and the Minnesota Pollution Control Agency (which manages water-quality issues related to mines). Some private companies own mine sites, but they are under permit and regulation by the DNR or the MPCA, officials say.

East slope of the Soudan underground mine's 27th level.
Minnesota Department of Natural Resources
West stope of the Soudan underground mine’s 27th level.

There was little oversight involved in Colorado’s Gold King mine. In 1872, the federal government approved the General Mining law, which meant anyone could stake out a claim on federal land for no fee and start mining for things like platinum, gold, silver, copper and lead. Individual miners and small groups began digging veins and tunnels into mountains to find gold. Since there was no environmental regulation to speak of, miners simply left the Gold King mine behind in the 1920s when the money dried up. The mine was passed among private owners for years afterward, with local officials in nearby towns hesitant to wade into talks of environmental protection.

“The state of knowledge now — for both the industry and for regulators — is vastly superior,” says Richard Clark, who works in the mine supervising division of the MPCA. “Those mining methods and waste management methods would not be allowed now.”


A major reason Minnesota’s abandoned mines are less risky than others boils down to geology. When metals like gold are mined, they are extracted from sulfide ore. When water hits sulfide ore, it can turn into acidic drainage. After Gold King’s operators abandoned the mine in the 1920s, they left sulfide exposed in open tunnels that filled with snowmelt and rainwater. Minnesota’s iron ore is found mostly in oxide ores, and there is a very low rate of sulfide extracted in typical iron ore mining. And unlike sulfide ore, when oxide ore is exposed to water, it turns to rust.

Which isn’t to say regulators and environmentalists don’t have any concerns about Minnesota’s abandoned mines. A handful of old mining or drilling sites are problematic and are maintained or monitored by state officials. That includes the former Soudan underground iron mine near Lake Vermilion, which is now a state park. In 2006, the DNR was fined by the MPCA for discharging water from the site that exceeded some water-quality standards.

And while Minnesota has not conducted so-called sulfide mining like Colorado, several companies have drilled to explore metal possibilities under the state’s surface. In the 1970s, a company called International Nickel drilled exploratory holes at a site near Ely. Another company, AMAX, conducted similar drilling near Babbitt. The iron mine Dunka Pit, run by LTV Steel Mining Company, excavated a significant quantity of sulfide ore to access iron buried beneath it, and some of the sulfide ore was found to be leaching contaminants into Birch Lake’s Bob Bay, in violation of water-quality standards.

The future worries environmentalists more than the past

Many old mines are now simply open pits, which are monitored for safety. Underground mines can cave in, rocks can fall from pits, and they are often dangerous after a big rainfall. The IRRRB puts up fences and can patch up vertical shafts in old mines if they open up, says Dan Jordan, who works with IRRRB’s Mineland Reclamation Division. Depending on the community, reclaimed mines have also been turned into business parks, fishing piers, campgrounds, overlooks, gun clubs — even a blueberry patch.

Environmental groups are still worried about water contamination from mining, though their concerns arise more from active mining and proposed projects than from abandoned sites. State and federal environmental groups, including the EPA, are worried state pollution officials haven’t developed a clear plan to deal with waste rock and polluted water from the Minntac mine in Mountain Iron, for instance, which is leaking pollutants into the St. Louis River Watershed.

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Steve Morse
Steve Morse

Even more, environmental groups are protesting the proposed NorthMet Project — better-known as PolyMet for the company that is planning it — which hopes to tap into one of the world’s largest known undeveloped deposits of copper and nickel near Hoyt Lakes (within the Lake Superior Basin) via sulfide-ore mining. Twin Metals, another proposed sulfide mining project, is several years behind NorthMet in the permitting process, but the project would directly affect Ely and the Boundary Waters Canoe Area Wilderness watershed.

“The lesson of [Colorado] is that these are highly dangerous activities, they are risky activities. When things go bad they go really bad and have really catastrophic impacts,” says Steve Morse, executive director of the Minnesota Environmental Partnership. “It’s the sulfide mining projects that are the biggest concern … we have these rose-colored glasses on as we look at it at this point. People just assume things are going to work, but this is a really dangerous thing we are doing. It’s kind of like playing with nuclear weapons.”