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Why proposed solutions to sulfide-mine pollution won’t work

Financial assurance, reverse osmosis and compromise have been promoted as viable ways to protect Lake Superior and the BWCA.

boundary waters
Sulfide mining threatens two of the greatest water resources in the nation, Lake Superior and the Boundary Waters Canoe Area Wilderness.

Despite machinations by PolyMet Mining Corp. and the Minnesota Department of Natural Resources to camouflage the fact, Minnesota’s Arrowhead is facing perpetual pollution and water treatment from PolyMet’s NorthMet Project, if its mine is permitted.

Financial assurance, reverse osmosis and compromise have been promoted as solutions to sulfide mining in Minnesota, as viable ways to ultimately protect two of the greatest water resources in the nation, Lake Superior and the Boundary Waters Canoe Area Wilderness.

Then there are always the familiar standbys: ignorance and delusion.

Financial assurance is not the answer. It is not the answer for one simple reason. If a bonding company does take on the risk of PolyMet or any other sulfide mine, PolyMet’s SDEIS indicates there is high probability that sulfide-mining contamination of surface water, sediments, ground water and soil cannot be cleaned up in our lake district. Money cannot fix the unfixable — or replace the irreplaceable.

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Reverse osmosis is not the answer. Sulfide mining in water-intensive areas has never been done without contaminating surrounding waters. Reverse osmosis is not “new” technology. It has been around for decades. If it could solve water contamination caused by metal mining it would have done so by now. Reverse osmosis cannot even solve water pollution at Minnesota’s taconite mines, which are operating under variances or expired permits. In addition, in Minnesota, mining permits are often written to deliberately leave out or weaken important contaminant parameters.

The company neglects to point out that reverse osmosis will only treat part of the contamination from PolyMet’s proposed NorthMet Project, only treating discharge water at the end of the 20-year operation; it will not treat water going to the tailings basin for the proposed 20 years of production. As multiple types of waste chemicals concentrate in the basin (alleged in the proposal as a closed system) the treatment will become less effective, (e.g. 80% of 1000 ppm leaves 200 ppm, 80% of 2,000 ppm leaves 400 ppm). Keep in mind that many of the stream standards are in the parts-per-billion level.

A filtration system is only as good as the water you put into it. The proposed closed loop system of PolyMet is comparable to leaving a gallon of dirty water (total dissolved solids) in the bathtub each time you take a bath. All mining companies say they will have no discharge and will keep recycling. However, it does not work that way. Minntac is a closed system. The only solution to its contaminated wastewater is to contaminate surrounding waters. Reverse osmosis was tested for Mesabi Nugget and it was found to be too costly or it did not work. The company could not meet standards and obtained a variance to violate Minnesota’s water-quality standards.

Reverse osmosis for PolyMet is not scientifically defensible. No testing has been done that is relevant to the actual mining and treatment situation for this application. No substantive data indicates that reverse osmosis will work to fully meet water-quality standards. In PolyMet’s case reverse osmosis was tested, but using what? It is unclear just what was run through the reverse osmosis system. Was wastewater used from its mineral extraction bulk sample testing? Compared to what PolyMet proposes to actually run through a full-scale treatment system, the “real” water will be much worse. Pre-filter plugging and reject water disposal will be major issues. PolyMet underestimates the quality and quantity of input water that will need to be treated.

All filtration systems (reverse osmosis and nano-filtration) require backwashing (backflushing) the pre-filters and the final filter. Since the pre-filter waste is a concentrate of the input wastewater, it will likely be aquatically toxic. Depending on the quality of the input water, up to 40% of the input water can be this reject back flush. The proposal is to return reject water to the tailings basin. Sludge may go to a landfill, but is untested and likely to be aquatically toxic. Precipitation (rain, snow) will impact the hydrometallurgical residue facility (solids dump). The solids dump will cause leaching. Since the waste particles will be similar to silt or clay, treatment of the solids to prevent toxic leachate will be difficult if not impossible to treat into perpetuity.

Ignorance is not the answer. PolyMet takes only a small number of samples in its environmental testing processes, which does not represent what will occur in the real world. The heterogeneous mixture of rocks is not consistent and small samples cannot reflect anywhere near actual field conditions. This can be demonstrated with field data from both the Dunka mine and MinnAmax, which has demonstrated that water quality is much worse than the small-scale lab testing that has been performed. This difference is caused by the heterogeneity (disseminated) nature of the entire deposit; one spot will have lots of sulfur, another spot will have little sulfur. They have only taken a very limited number of environmental laboratory samples in this heterogeneous deposit. In comparison, to evaluate the economics of the minerals, they report taking thousands of analyses to define the 1% of the minerals that are of economic interest.   

The mine pits will eventually fill with water. The north wall of the East pit is Virginia Formation. It is well documented that this formation contains high sulfates and other heavy metals. This fractured mineralized wall will leach acid and metals. The mine pits will eventually discharge, carrying contaminated pit water to the wetlands and the Partridge River. “The East Pit, West Pit, and Category 1 Stockpile are permanent features that would continue to provide solute-loading [metals and sulfate] for a minimum of 200 years.” (SDEIS) How the agencies picked a minimum of 200 years is a mystery; nothing is going to stop it. Take a look at the toxic Berkeley Pit if you want a preview.

The current PolyMet mine is designed for the 100-year storm (a 1980s statistical description of a 1% chance of a very high precipitation storm); given climate change, this design is insufficient. Scientific studies suggest the facility must be designed to withstand a 500-year storm, because the 1980s’ 500-year storm is now occurring almost as often as the 100-year storm. For PolyMet this is critical; it must be able to manage huge volumes of wastewater. If the storage and/or treatment system is insufficient, untreated wastewater overflows to the nearest stream partially treated or untreated.

Compromise is not the answer. In the news recently the sulfide-mining issue has been portrayed as an internal DFL problem; it is far bigger. This is a political issue that has crossed party lines. This is about Minnesota, not about any political party. Minnesotans love their lakes. They care about their children’s health. Republican or Democrat.

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Sulfide mining is not an issue solved by “compromise,” as some suggest. Compromise what? There is no acceptable trade-off for perpetual water pollution and increased neurological damage to our children, some of it inheritable, for unknown numbers of generations. Compromise how? By selling out our children and our waters? That’s hardly a solution in the public’s best interest.

The answer: PolyMet’s SDEIS “No Action Alternative.” No permit. No sulfide mining in Minnesota’s Arrowhead.

C.A. Arneson lives on a lake in the Ely area.

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