TWO mines, one threat

Foreign corporations are trying to open copper-sulfide mines in Minnesota, which threaten to pollute some of the cleanest water in the country 

Photo courtesy of    Benjamin Olson

Photo courtesy of Benjamin Olson


What is copper-sulfide mining?

Sulfide mining, which is sometimes referred to as hard-rock mining, is the process of extracting trace amounts of copper, nickel and other metals from sulfide ores.

When sulfide ore comes into contact with water or oxygen, a chemical reaction occurs and produces sulfuric acid, which is the same as battery acid. 

In addition to acidifying lakes and rivers, sulfuric acid leaches out heavy metals such as mercury, lead, arsenic and other toxins from the rock to produce Acid Mine Drainage. 

Because of its inherently polluting nature, the EPA has been called hard-rock mining (or sulfide mining) the most toxic industry in the country

In fact, there has never been a sulfide mine that has not polluted surrounding water sources. 

Even worse, the pollution from sulfide mining is nearly impossible to contain and can last for hundreds, even thousands of years. More often than not, it is the taxpayers who are left to pay the cleanup bill. 

It’s all but guaranteed that Acid Mine Drainage from these mines will contaminate the groundwater and seep into surrounding lakes and streams. If opened, these mines would cause irreparable damage to northern Minnesota.


Copper sulfide mining has never been done in Minnesota. It is much different than the traditional form of iron mining that has such a rich history in the state.

Sulfide mining is especially dangerous in northern Minnesota because of two factors: The water-rich environment and the low-grade quality of the mineral deposits.

1. WATER The clean water and seemingly endless waterways that make so many people treasure northern Minnesota’s wilderness, would also amplify the effects of Acid Mine Drainage.

The pollution produced by these mines would not stay contained in one localized area. As water moves, the streams and lakes and rivers would act like as a conveyor belt that would spread the pollution over millions of acres.

Detail of where the proposed mines would be, showing the path the pollution would follow, in orange.

Detail of where the proposed mines would be, showing the path the pollution would follow, in orange.

2. LOW QUALITY ORE DEPOSITS The Duluth Complex, which is the mineral body where these companies want to mine, has very low quality deposits. Less than one percent of the rock contains copper or any metal of value. The best estimates conclude that only between .3 and .6 percent of all the rock mined would contain copper.

That means between 150 and 300 pounds of rock would need to be pulverized to produce a pound of copper that, as of August 23, 2019, is valued at $2.56 a pound.

To be profitable, these mines would need to move and crush millions of tons of rock to extract a relatively small amount of copper, nickel and other metals. 

In turn, this would create a huge amount of waste rock that has been exposed to water, to oxygen, and therefore, would be producing an enormous amount of sulfuric acid.

This toxic slurry of pulverized rock and sulfuric acid needs to be stored in a tailing basin. Even in the best circumstances, when everything goes as planned and no accidents occur, it’s impossible to prevent the sulfuric acid from seeping into the ground water and contaminating the rivers and streams.

Currently, there are two proposed copper-sulfide mines in Minnesota: PolyMet and Twin Metals.


At the doorstep of the Boundary Waters, is the site of the proposed Twin Metals mine. 

Photo by Benjamin Olson

Photo by Benjamin Olson

Owned by the Chilean mining conglomerate Antofagasta, the Twin Metals mine would be an ecological disaster for the most-visited Wilderness Area in the United States.

Water is the lifeblood of the BWCA. Because the geology of the BWCA is such that it can’t buffer or effectively absorb Acid Mine Drainage, pollution from the Twin Metals mine would spread over two million acres of pristine water, including the Quetico Provincial Park and Voyageurs National Park.

Despite widespread public opposition to mining in the Boundary Waters watershed, the Trump administration rolled out the red carpet for Antofagasta and stripped away hard-won protections for the Boundary Waters. In response, Friends of the Boundary Waters Wilderness and our partners sued the Trump Administration for illegally giving away public land to Antofagasta.  


PolyMet, which is approximately 12 miles south of the border with the Boundary Waters, is the snow plow that will clear the way for other copper-sulfide mining in Minnesota, including the Boundary Waters watershed.

Though it is in the Lake Superior watershed, PolyMet is close to becoming the first copper-sulfide mine to begin operations in Minnesota and will set the precedent for future mines near the Boundary Waters.

The Partridge River, near the proposed PolyMet Mine site. Photo by Rob Levine.

The Partridge River, near the proposed PolyMet Mine site. Photo by Rob Levine.

In November, 2018, Minnesota DNR issued the final state permit for PolyMet. They did so despite many concerns raised by scientists, engineers, financial experts and the public. 

One of the most frustrating parts of this was that DNR is allowing PolyMet to use a cheap but dangerous type of dam to contain the mining waste. This is the same type of dam that collapsed in Brumadinho Brazil, killing over 200 people.

This type of dam construction has since been banned in Brazil.

But for some reason this kind of risky engineering is safe enough for Minnesota?

Shortly after PolyMet received the final permit it needed to begin operation, it was revealed the the Minnesota Pollution Control Agency (MPCA) along with higher ups at the EPA attempted to suppress concerns that the wastewater permit would allow PolyMet to violate the Clean Water Act. 

In response, Minnesota Court of Appeals stayed the permit until an investigation into these irregularities (which is a generous way of putting it) was completed. 

An open pit similar to the one proposed by PolyMet

An open pit similar to the one proposed by PolyMet

Minnesotans like to think they “have the strongest environmental regulation in the world” but what this scandal shows, along with how DNR turned a blind eye to the issue of dam safety, is that the permitting process is deeply flawed. 


Recently, another mining company, Encampment Minerals, announced plans to begin exploratory drilling near the Boundary Waters

Twin Metals and PolyMet are only the beginning. There are over 40 pending hardrock mining permits within the Superior National Forest. Copper-sulfide mining could radically transform the area. What was once the home of America’s most visited Wilderness Area, may well become an industrial corridor for the most polluting industry in the United States. 

We must stop these two mines before that happens.



Clean water Minnesota

Clean Water

Water is our most precious resource. At a time when fresh water scarcity affects all corners of the globe, it’s important to realize how unique it is to have so much pristine water in northeaster Minnesota. Like the Grand Canyon, Yellowstone or Yosemite, this unique abundance of clean water should be cherished and protected as the rare treasure it is.

child in the Boundary Waters


Millions of people have experienced the power of the Boundary Waters. In our busy, digitized world, the BWCAW offers a chance for solace, for adventure and to reconnect with others. We go to the wilderness push our limits, to discover something new about our world and ourselves. If these mines were to open and pollute, we would lose an essential part of our heritage

Photo courtesy of Bobby Marko

The Local Economy

Multiple studies show that while sulfide mining would give an initial bump to the economy, it would leave the region with a long, economic hangover. A robust, sustainable wilderness economy has grown around the communities surrounding the BWCAW. During the summer, tourism has a $77 million impact and creates 1,000 jobs. Manufacturing has also resurfaced in the area. However, this economic engine depends on the wilderness character of the region.