Risks to Clean Water

Sulfide Mining Overview | Risks to Clean Water | History of Pollution | Threat to the Economy | What You Can Do

Sulfide mining kills and contaminates fish, makes water unsafe to drink, and harms entire ecosystems. Such mining has never been done in Minnesota before, but has caused devastating pollution all over the country and the world.

America’s Biggest Source of Pollution

Every year, the Environmental Protection Agency analyzes where pollution in the United States comes from. In 2010, the metal mining industry was once again the biggest source of pollution in the country.

Such mining was found to be responsible for 41 percent of all polluted discharges tracked by the EPA — the next biggest polluter was coal-fired power plants, at just 18 percent of the country’s pollution.

“Since the metal mining industry started reporting its releases in 1998, the TRI has shown that it is the largest toxic polluter in the United States. In 2010, the metal mining industry reported releasing 1.6 billion pounds of toxics or 41% of all toxics reported.

“For selected bioaccumulative toxics, metal mining accounts for the vast majority of all toxics reported. For example, in 2010, metal mining accounted for 96% of all arsenic releases and 92% of all mercury releases.” – Earthworks

Minnesota: Land of Bright Orange Waters?

Spruce Road Acid Mine Drainage

Two miles from the BWCAW, acid mine drainage seeps out of waste from a small 1970s excavation

The problem is that when water and air come into contact with the massive amounts of waste produced by this type of mining, sulfuric acid is created (with the same process in Minnesota’s traditional iron mining, rust is produced). This acid leaches out toxic metals from the waste, and then contaminates nearby water bodies.

At metal mines, the target ore (like gold, silver, copper, etc) is often rich in sulfide minerals.

When the mining process exposes the sulfides to water and air, together they form sulfuric acid.

This acid can and often does dissolve other harmful metals and metalloids (like arsenic) in the surrounding rock.

Acid mine drainage can be released anywhere on the mine where sulfides are exposed to air and water — including waste rock piles, tailings, open pits, underground tunnels, and leach pads. – Earthworks

Acid mine drainage has been a serious problem in states like South Dakota, Montana, and New Mexico. The U.S. Forest Service estimates that, in the Western states, 5,000 to 10,000 miles of streams have been polluted by such mining.

Impacts to fish and wild rice

One key pollutant from sulfide mining are sulfates — a salty compound that is largely harmless on its own, but when large quantities are released into the environment, it can have harmful effects:

  • Increased mercury contamination of fish – Sulfates increased the “methylation” of mercury, essentially facilitating the consumption and accumulation of mercury in fish. This makes fish dangerous to eat, with the potential to harm brain development, and especially the healthy of mothers and children.
  • Destruction of natural wild rice – Sulfates also harm wild rice, Minnesota’s state grain, an important food source for many people, and a significant cultural resource for the Ojibwe.
Wild rice

Wild rice in northern Minnesota, photo by Eli Sagor

The standard for sulfates discharges into wild rice waters has become a key point of contention in the debate over sulfide mining in Minnesota. The current standard, which allows for levels of 10 mg/liter, is based on extensive research done by University of Minnesota – Duluth and Department of Natural Resources researchers in the 1940s and widely reviewed by other scientists.

One of the researchers who helped with the wild rice sulfate study was Len Anderson. Anderson wrote this about his work:

“That science is the seminal work of John B. Moyle and his published peer reviewed research. I had the privilege of working in wild rice stands and reporting to him in the late 1950s. In about 1961 I asked him why he was so interested in wild rice and he said it was intriguing to him. That is pure science. He was not working for any vested interest. He was a DNR scientist trying to understand an important part of the natural world. His methodology was to observe and document hundreds of wild rice stands and then to analyze the abiotic conditions that supported them… In Moyle’s analysis, published in the Journal of Wildlife Management, Vol. 8, No. 3, July 1944, he said “No large stands of rice occur in waters having a SO4 content greater than 10 p.p.m., and rice generally is absent from water with more than 5 p.p.m.”

In the courts, the Minnesota Chamber of Commerce has sued the state to stop enforcement of the standard, while in the legislature, a bill was passed in 2011 to re-examine the standard. The new study could result in a weakened standard more friendly to mining but disastrous for the dwindling stands of natural wild rice in the state.


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