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A dam collapse in Brazil has some worried about PolyMet’s plans. Why the DNR says it won’t happen here

Brumadinho dam break
REUTERS/Washington Alves
A view of the Vale dam that burst, in Brumadinho, Brazil, on January 25.

In January, the tailings dam at a Brazilian iron ore mine collapsed, killing nearly 250 people. The wave of toxic waste and mud also wrecked two dozen buildings and polluted water for five miles.

In Minnesota, the disaster raised eyebrows among opponents of a copper-nickel mine planned near Hoyt Lakes. That’s because the design of the dam in Brumadinho was similar to one PolyMet Mining hopes to build. In fact, the Vale mining company had used a method to judge dam safety created by a PolyMet adviser. And the tragedy in Brazil embodied the worst fears of some Minnesota environmental activists and the Fond du Lac Band of Lake Superior Chippewa, who warn PolyMet could pollute the St. Louis River.

Those groups, and some DFL state legislators, recently asked state regulators to reconsider authorizing PolyMet’s mining plan. “The DNR must modify the tailings … storage permit to require best practices, like dry tailings storage,” which don’t require a pond or dam, says a letter last month signed by 18 Democratic lawmakers. “Minnesota should accept nothing less after the tragic collapse of a similar tailings dam in Brazil that killed 250 people.”

The state Department of Natural Resources, however, says any similarities between PolyMet and the Brumadinho dam are limited. DNR Commissioner Sarah Strommen announced last week the agency would not change two critical permits granted to PolyMet last year after researching what happened in Brazil.

“We understand people’s concerns with these dam failures and whether those events indicate a fundamental design issue with PolyMet’s dam,” Strommen said in a news release. “Our analysis demonstrates that there are significant differences in site conditions, engineering design, and operating requirements and we remain confident in the safety of the PolyMet tailings dam as permitted.”

Here’s what we know about the criticism of the PolyMet’s tailings dam — and why state regulators approved it:

Same construction method as Brazil dam

Those who aim to stop PolyMet because it carries a risk of acidic runoff and water pollution have long criticized the company’s tailings dam. PolyMet expects to repurpose an existing tailings basin once owned by LTV Steel Mining for processing taconite. Waste from the mine is covered in water in a tailings pond, and the slurry is held back by a dam. 

A consultant hired by the DNR to research the state’s financial protections with PolyMet — but not dam safety specifically — has said the setup approved by DNR was “inherently unstable and irresponsible” and “will eventually fail.” Environmental groups have often used those words to recommend PolyMet switch to “dry stack” tailings, in which the company drains water from tailings and piles the sand-like remains.

three types of dam construction
Minnesota DNR
A graphic in a state DNR dam safety permit for PolyMet, showing three types of dam construction. PolyMet's use of the 'upstream' method is controversial, as the 'upstream' method was used by Vale mining company at the Brumadinho mine.
Twin Metals Minnesota, a company hoping to build a copper-nickel mine near the Boundary Waters Canoe Area Wilderness, recently announced it would use dry stack technology for much of its tailings, rather than covering the waste in water.

After the collapse in Brazil, PolyMet’s opponents once again raised questions about the possibility of a similar disaster in Minnesota.

The PolyMet dam will be built using what’s known as the “upstream” construction method, a common design in which the dam is built upward in step-like stages, slanting inward toward the center of the tailings basin. Upstream construction was used at the Brumadinho dam, and Brazil banned the method after the collapse. “It is shocking that Minnesota would permit PolyMet to open a new mine using such a risky system, when even Brazil now prohibits them,” the letter from DFLers says.

PolyMet also used the Olson Method — a safety assessment used to analyze the strength and stability of a tailings dam — and hired its creator, Scott Olson, as a consultant. The method was also used in Brazil for the Brumadinho dam.

In response, environmental groups such as WaterLegacy and Duluth for Clean Water, as well as the Fond du Lac Band, asked the DNR to reconsider PolyMet’s Dam Safety Permit and a Permit to Mine.

DNR: PolyMet is different

The DNR has dismissed the idea of PolyMet using dry stacking. The tailings storage is less feasible in wet environments, the agency says, and re-using the LTV Steel facilities would have less impact on wetlands, since the tailings basin PolyMet would repurpose already exists. 

Twin Metals plans to put about half of its tailings back into its underground mine, especially during cold and wet conditions. Since PolyMet is an open-pit mine, that is not an option and would risk pollution from a wet tailings pile, said Jess Richards, an assistant commissioner at DNR. PolyMet also intends to collect and treat water from the tailings basin to stop polluted seepage currently happening at the old LTV site.

“So it’s not as simple as to say, ‘let’s just build a different tailings basin,’ ” Richards said in an interview.

Before the collapse in Brazil, the DNR’s regulators approved the idea of a tailings dam and basin. Their team included a member of panel that investigated a 2014 dam failure at the Mount Polley mine in British Columbia (which did not use an upstream design for its dam).

Still, Richards said the DNR “took a hard look” at concerns from the Fond du Lac Band and the environmental groups over several months. Their conclusion: PolyMet’s proposed dam is much different from the Brumadinho one in Brazil, Richards said.

First, the dam in Brazil was steeper and perched on the side of a mountain. PolyMet’s dam will be flatter and “on relatively flat ground,” says Strommen’s order affirming the permits. The Brumadinho dam also had a significant amount of water flowing into the tailings basin that was piped away from the area, the letter says. The order notes reports that the pipeline breached, causing water to spill into the basin for several weeks before the dam collapsed.

The dam in Brazil was also more at risk of earthquakes and near active mining operations and mine blasting that “threatened the stability of the dam,” Strommen wrote. In Minnesota, actual mining will be done about eight miles from the tailings basin.

Lastly, Strommen’s letter says the DNR independently reviewed Olson’s work. Olson himself did not review the Brumadinho dam’s stability analysis, and told the state it was used incorrectly in Brazil. Richards said the DNR checked whether the dam could fail in extreme circumstances, such as if there was “full liquefaction of the basin,” extreme rainfall or an earthquake.

“There’s a real big difference in the level of rigor and conservative assumptions that were put into the PolyMet analysis compared to the Brumadinho dam in Brazil,” he said.

Comments (19)

  1. Submitted by Elisa Wright on 08/13/2019 - 11:46 am.

    There are so many reasons Minnesota environmentalists do not like this Polymet/Glencore project. They also have a bad reputation when it comes to human rights & have had problems with their unions in other countries. Why are we so desperate for their jobs & why has Polymet put up with setbacks & environmental rules for so long? What’s in it for everyone that this project wasn’t abandoned long ago?

    The Democrat reasoning seems to be that this project has been around for a long time. It isn’t their fault. As long as the appropriate permits are issued, it’s out of their hands simply because there’s no law against it. They can’t make any new environmental laws because of the Republicans. Some Democrats even support the project.

    • Submitted by Christopher Williams on 08/14/2019 - 07:38 am.

      By “Some Democrats even support the project.”, you of course mean Amy Klobuchar and Tina Smith – both strong supporters of this project.

  2. Submitted by Elanne Palcich on 08/13/2019 - 12:58 pm.

    The former LTV tailings basin is already leaking. Cleveland Cliffs has handed the responsibility over to PolyMet. There’s more behind the scenes than is being presented here.

  3. Submitted by William Hunter Duncan on 08/13/2019 - 01:30 pm.

    Curious the DNR should be so confident about the future of the Polymet tailings dam, when this MN government did such a poor job watching over the Hector Mine Pit dam outside Biwabik Mn, that collapsed in 2018, spilling mine tailings into the Embarrass river (ironically, one would think this gov would be embarrassed about that.)

    Of course 70 years from now those responsible for Polymet etc copper/nickel mining will not be alive to answer for their decisions, which apparently is not this generation’s problem.

    (I tried to link an MPR story about the hector mone dam, but Minnpost just deletes the whole comment.)

    • Submitted by richard owens on 08/13/2019 - 04:38 pm.

      Here you go William:

      ““When we consider the recorded life of tailings dams structures (a century at most) compared to the length of time that they must function (millennia), the number of failures observed in the first century of their operation is not comforting,” wrote David M. Chambers in a report to the National Forest Service. “The statistics suggest a rather severe underestimation of risk continuing even today in tailings dam permitting and construction. Our society still does not fully appreciate the long-term implications of storing billions of tons of potentially-harmful and semi-fluid waste in large impoundments.”

      • Submitted by William Hunter Duncan on 08/14/2019 - 03:39 pm.

        Thank you, Richard. Precisely what I keep saying about this. No one has any right to force future generations to deal with our pollution…but that does not matter to those who will profit from this. Like the old adage goes…”So what, I’ll be dead when it becomes a problem.”

        Faith that future generations can take care of this (or that this generation can) reminds me a lot of my Christian friends when I talk about ecological destruction leading to pollinator extinction, soil loss and pollution eventually leading to human famine, etc: ‘God would never let that happen.’

  4. Submitted by Dave Paulson on 08/13/2019 - 01:50 pm.

    From Stommens letter, Dr. Olson consulted for the Brazilian mining company for 2+ years before their dam failure, but not on the dam safety during that time “which he did not review”. Then Olson claims his method was miss-applied, so he must have reviewed the original analysis AFTER the dam failure, when he would have a very strong incentive to find flaws in the application of “his method”.

    The DNR would be more persuasive if they named their so-called outside consultants who looked at the dam model, and gave us their credentials, exact technical conclusionsand what data they started with. We only have Polymet’s word for the opinion of Dr. Olson their consultant.

    Given a dam failure and 250 dead, and dam design analysis with the “Olson Method” this design analysis should should be both picked apart and transparent as possible. Remembering all the game-paying and obfuscation that occurred around the 35W bridge collapse, we should be skeptical of state agencies risk analysis.

    And it matters not to the actual veracity of the final decision criteria how long the review has been underway. For the same length of time Polymet has been making changes to the mine plan and submitting new information (as it should be). And whether it took one minute or 2 decades the final fact set is just as correct.

  5. Submitted by joe smith on 08/13/2019 - 05:07 pm.

    Dam was built in early 1970’s. Not sure it is even applicable to 2019 standards and building in USA versus Brazil.

    • Submitted by richard owens on 08/14/2019 - 10:33 am.

      50 years is a long time for a human being or a family, but for geological forces, it is but a blink in time.

      The permits use the phrase “perpetuity” to describe maintenance agreements on these containment ponds. Like cemeteries, “perpetuity” is something we can hardly imagine, let alone plan to budget for or to administer.

      And yet our agreement with the companies will require enforcement, and some way to pay for maintenance long after the company and the resources are gone. Given our propensity to have institutional memory loss, it isn’t likely the end times of the agreement (when we’re dead and gone) will be faithfully executed by politicians and legislators who will have other concerns than tailings berms.


      In more recent history, the IRRRB is an example of Minnesota’s attempt to plan for the “end of mining”, and restore both the land and communities from the depressed and barren state they were in before taconite gave one more economic push.

      As a Ranger (or familiar visitor, as you may be, Joe) you would be very interested I think in this: a three part series on the history of NE MN through the 20th century and into the taconite era.

      Good reading!

      “After the Mines: Can the IRRRB Help the Iron Range Prepare for the End of Mining?
      By Bob Kelleher and Amy Radil
      December 6, 1999


      “Part One: The History
      Once a wild paradise of clear lakes and pine forest, mining and logging transformed the Iron Range into a dingy desert of huge open pit holes and scraggly second growth woods and stumps. After just 50 years of intensive mining, Minnesota’s reserves of high-grade iron ore, once thought inexhaustible, were nearly spent. Meanwhile, the Great Depression had idled America’s industries and forced Minnesota’s iron miners into work camps and soup lines. Demand for steel was absolutely flat. A workforce of 12,000 miners in the 1920s shrank to less than 2,000 in the 1930s.

      • Submitted by joe smith on 08/14/2019 - 12:24 pm.

        The answer to the question of can the IRRRB help reconstruct the Range is a resounding no!!! The IRRRB has wasted money, time and worst of all hope up here. I’m not sure how much time you’ve spent up here but mine pits are few and far in between, definitely much less than 1% of the Range is mining pits. We have mature full growth forests all over the North East. As a matter of fact, we need to log Federal land to reduce all the standing dead timber that will eventually burn if not harvested. Trees have a life span and will fall, burn to regenerate the forest just like it has happened for thousands of years.

  6. Submitted by Joe Musich on 08/13/2019 - 10:07 pm.

    I would like to se the Hector mine study reported here. This seems to be an aoorioriate place for the kink to be presented. After all oversight is the go to word that nring us here.This seems to be an example where failure in our own state mining industry occurred.

  7. Submitted by William Hunter Duncan on 08/14/2019 - 03:48 pm.

    I wonder if supporters of this would still care so little for future generations if we passed a law that said the descendants of those who profit from this mining are financially responsible for cleanup, in perpetuity?

    Of course that would be immoral. But apparently, making somebody else’s descendants pay for it is not….

  8. Submitted by Ralph Wittcoff on 08/14/2019 - 04:56 pm.

    This stuff is toxic for 500 years. If a flood such as occurred in 2012 were to occur after this travesty is built, Knife River, not to mention Duluth, will be under four feet of sulfuric acid. Once again: A 900 acre lake of sulfuric acid sludge behind an earthen dam just up the hill from Lake Superior — what could go wrong? Time to replace the DNR with an agency which actually protects our natural resources (and realizes that fresh water is our most valuable natural resource). And time to replace the MPCA with an agency which actually protects us from pollution. Out with stooges for international corporations.

  9. Submitted by Paul Udstrand on 08/15/2019 - 09:21 am.

    We do have earthquakes in MN every once and an while, no one can claim we won’t have one ever again or in the next 200 years or whatever. There’s a difference between considering a problem and dismissing a problem. I always get nervous when someone claims to have “considered” extreme weather conditions because time and time again we find that systems are overwhelmed by conditions no one anticipated, despite having claimed to have anticipated them.

    I think in a scenario like this the risk needs to zero, that’s a high bar but it’s the only bar that makes sense because failure can’t be an option.

  10. Submitted by richard owens on 08/15/2019 - 04:51 pm.

    A little off-topic, but NEWS: The Koch brothers, who have pushed Minnesota to approve pipelines for Alberta’s Tar Sands, have decided to exit the Tar Sands business by selling their stake and releasing other leases.

    This is victory of sorts, as many of the biggest players are no longer invested in Canadian bitumen.

    “In the years prior to the asset sale, Koch has blamed the Alberta NDP government for the regulatory uncertainty that, the company said, forced it to suspend a planned US$601-million (C$800-million) project in the province.”

    “Even earlier than that, Koch said Canada’s signing of the Kyoto Accord on emissions reduction was the reason for it to abandon another project, Fort Hills, which would have sucked in some US$2.6 billion (C$3.5 billion) in investments. Fort Hills is now Suncor property and operating, despite the Kyoto Accord.”

    When the biggest fossil fuel players see the writing on the wall, the world can only get cleaner, faster.

    I doubt Enbridge will get the new pipelines they think they want.

  11. Submitted by Julie Stroeve on 08/16/2019 - 09:40 am.

    Where’s the prohibition to declaring bankruptcy after all the mining is over? Bankruptcy is the company’s M.O. Private profits and social bailouts. Unless I see a guarantee by the Brazilians that it will build unbreakable storage and prevent sulfuric acid poisoning of our lands, air and water, I’m a no go on PolyMet.

  12. Submitted by Jim Grinsfelder on 08/21/2019 - 07:14 am.

    Glencore is refusing to accept liability for Polymet (they own 70% of Polymet). This project should not go forward. Polymet will extract the metals, Glencore will extract the cash. Minnesota and US taxpayers will be left with the mess. Privatized profits and socialized costs, no thanks.

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