FAQ: Everything you need to know about PolyMet

Polymet CEO Jon Cherry
PolyMet CEO Jon Cherry at one of his company's buildings near Aurora, Minn.
Derek Montgomery / For MPR News

What is PolyMet proposing?

PolyMet wants to mine copper, nickel and precious metals for 20 years at a site located just north of Hoyt Lakes in the Superior National Forest. The NorthMet Deposit is part of what is known as the Duluth Complex, which stretches from about 150 miles north of Duluth all the way to the Canadian border. PolyMet would build three open pits and blast and drill to get to the ore containing minerals. Ore would be put in rail cars and shipped seven miles west to an old iron ore processing plant — LTV Steel — which closed in 2001. PolyMet is repurposing the facility to process up to 32,000 tons of copper and nickel per day.

How significant are the deposits?

The Duluth Complex is considered one of the biggest copper-nickel deposits in the world. PolyMet's mine would tap into just a small part of that, with the possibility of expanding later. PolyMet's goal is to produce 72 million pounds of copper, 15 million pounds of nickel and 106,000 ounces of precious metals annually.


Story: PolyMet an economic opportunity or too environmentally risky?
Map: Sites of proposed copper-nickel mines
Photos: Ramping up to mine copper
Timeline: PolyMet's history in Minn.

How does this proposal compare to other copper-nickel mines in the U.S.?

PolyMet's mine would initially be much smaller than many of the open pit copper mines in states like Arizona and Utah. But it's bigger than two copper-nickel mines in the Midwest. The Flambeau mine in Wisconsin operated during the '90s and produced about 362 million pounds of copper over the life of the mine — what PolyMet hopes to produce in just five years of mining. One other Midwestern copper-nickel mine is currently under construction in Michigan's Upper Peninsula. The Eagle Mine owned by Lundin Mining is being built underground, where mining would take place for eight years. That mine would produce more nickel but less copper than PolyMet.

Haven't we been hearing about this for years? What's new?

The first draft environmental impact statement for the project was released in 2009. But the draft was sharply criticized by the U.S. Environmental Protection Agency, which determined that the project would result in unacceptable and long-term water quality impacts.

In 2010, the Minnesota DNR, the U.S. Army Corps of Engineers and the U.S. Forest Service agreed to prepare a draft supplemental EIS that would improve the initial draft. This new version includes a proposed land exchange with the Superior National Forest into the draft, which is required for the project to proceed.

It also includes improvements PolyMet has incorporated into the project, designed to further mitigate environmental impacts. They include a cut-off wall around part of the tailings basin to trap water leaking from the site and water treatment plants that use a technology called "reverse osmosis" to purify water before it's discharged off-site.

What is the environmental impact statement and what does it determine?

The EIS is a 1,800 page document that analyzes the potential environmental impacts associated with the proposed mining project and examines ways those impacts can be mitigated. The Minnesota DNR, the U.S. Forest Service and U.S. Army Corps of Engineers are jointly leading the study's development, with input from cooperating agencies, including the U.S. Environmental Protection Agency.

After at least a 45-day comment public period, the agencies will incorporate any changes into a final EIS. Then, each of the lead agencies determines whether the EIS is "adequate." To be deemed adequate, the Minnesota DNR's Steve Colvin says the EIS must analyze the correct information, respond to substantive public comments in an appropriate way, and follow the EIS process as defined by law.

What happens if PolyMet's EIS is deemed adequate?

Barring any lawsuits, PolyMet can then begin acquiring the more than 20 required federal, state and local permits to develop a mining operation. Much of the information collected and analyzed in the EIS will be incorporated directly into the permitting process.

The main permit the company needs from the DNR is called the "permit to mine." DNR officials say permitting decisions are made on the technical merits of the project and whether or not it meets state rules and standards. Ultimately the DNR Commissioner, currently Tom Landwehr, makes the decision on whether to grant permission to mine.

Why are environmentalists concerned about the proposal?

They say copper-nickel mining is much more dangerous than iron ore mining, because the minerals are trapped in rock containing sulfide. When that ore is unearthed and exposed to air and water, it produces sulfuric acid, which if not contained, can leach heavy metals and contaminate ground and surface water. That process is often called "acid rock drainage" or "acid mine drainage." Environmental groups say a copper-nickel mine has never operated without polluting surrounding waterways, even when environmental impact statements for projects have been approved. They say it's too risky to permit mines with this track record in a water-rich and sensitive environment that drains into Lake Superior (the PolyMet proposal) or the Boundary Waters (the Twin Metals proposed development).

They are also concerned that PolyMet could pave the way for other nearby mines. Currently eleven other companies are exploring for copper, nickel and precious metals in the surrounding area. If those mines are all approved, mining opponents fear the cumulative impact of the operations could have damaging effects not only on water quality but on the pristine wilderness character of the area.

How does PolyMet plan to contain pollution?

At the mine site, waste rock with the lowest sulfur content will be placed in a stockpile with a groundwater containment system. Remaining waste rock will be temporarily stored on foundations and liners, and eventually backfilled into the mining pit and covered with water to reduce the potential for acid generation. Water control systems will be installed to capture and treat water that has come in contact with waste rock or the mining pits.

At the processing plant site, PolyMet has proposed to build a groundwater containment system to collect water seepage from the tailings basin, which covers an area roughly two square miles in size. That water would then be funneled into a water treatment plant that would use "reverse osmosis" to purify the water.

What is reverse osmosis and how effective is it?

Reverse osmosis is a technology that forces water under high pressure through a semipermeable membrane that traps minerals, salts, chemicals and other impurities in the water. It's been used in water desalination plants since the 1970s. It's also employed at wastewater treatment facilities. More recently some mines have begun to use it to treat water before discharging it to the environment.

PolyMet is proposing to build a reverse osmosis water treatment plant at the processing plant site during mine operation, and a second facility at the mine site after closure. The company has built a test facility in Virginia where it has successfully processed about three million gallons of water. PolyMet officials say they added the technology to mine plans after the initial draft EIS was criticized by the EPA in 2010 to meet Minnesota's 10 mg/liter sulfate emission standard designed to protect wild rice.

Mine critics don't question the technology itself, but they're skeptical as to whether PolyMet will be able to successfully capture all the water at the mine site and from the tailings basin that will then be treated by reverse osmosis. For example, they say the bedrock under the tailings basin is fractured, and argue that some water will escape the site before it can be treated by reverse osmosis. They also say the technology is very energy intensive, and produces a byproduct known as "brine" that has to be disposed of properly. Finally, they argue that the technology is very expensive to run, and question who will pay to operate the plants if they're needed for up to 500 years or even longer after the mine is closed.

What does Minnesota law say about this kind of mining?

State rules governing nonferrous metallic mineral mining were written in 1992. They cover in detail reclamation standards that must be met, in addition to permit requirements and administrative procedures.

The rules lay out a goal for mining companies to close mines in such a way "that it is stable, free of hazards, minimizes hydrologic impact and release of substances, and is maintenance free." Critics of PolyMet's proposal say the long-term water treatment will require violates the spirit of Minnesota law. But the company and the DNR have said long-term treatment is allowed as long as all water quality standards are met.

Who would be responsible for cleaning up any pollution after the mine has closed?

State law requires mining companies to commit money up front to pay for any maintenance, water treatment or other cleanup that might be needed after the mine closes. This financial assurance can come in many forms, including cash, bonds and trust funds. State officials would decide when to officially close the mine and "release" the mining company from responsibility. If pollution were detected after closure, the state would be responsible for taking action to clean it up. Whether the state would have to cover those expenses would depend on what kind of financial arrangement had been made with the mining company.

How would PolyMet extract metal from rock?

The beginning of the process is identical to iron ore mining, which is why PolyMet is proposing to reuse LTV Steel's old taconite facility. Giant mills crush the ore to a fine powder, each particle about the diameter of a human hair.

But rather than using magnets to separate the iron after it's ground up, PolyMet will run the crushed up ore through a series of 10'x10'x10' floatation tanks, where different "collector agents" cause the metallic particles to stick to bubbles that froth to the surface. The foam is scraped off, the water squeezed out, and the result is a copper or nickel concentrate that will be sold for further processing.

How much rock needs to be mined to extract the metals?

PolyMet's ore body has a "strip ratio" of about 1.4 to 1. That means for every ton of ore the company digs up to ship via rail to the processing plant, they will have to move about 1.4 tons of waste rock. Then, within the ore itself, the metal content is roughly .75%, combined , for copper, nickel, and various precious metals.

PolyMet plans to process 32,000 tons of ore per day. That means, each day, to produce 240 tons of metal, the company will generate 76,800 tons of waste rock, that will either be stored at the mine site, or in the tailings basin. Or, put another way, PolyMet will move 320 tons of rock for every ton of metal it produces.

The mine site is located within the Superior National Forest. Is mining allowed on national forest land?

PolyMet owns the mineral rights to the NorthMet Deposit near Babbitt, but the U.S. Forest Service does not believe that gives the company the right to surface mine. The agency says that would be inconsistent with the Weeks Act, the law under which the Superior National Forest originally purchased the land.

To eliminate that conflict, PolyMet has proposed a land exchange with the Forest Service as part of the EIS. Under the exchange, the company would trade several privately owned tracts of land inside National Forest boundaries in St. Louis, Lake and Cook Counties, for the land where PolyMet wishes to mine.

When would mining begin?

The second half of 2015, at the earliest. Assuming the regulatory agencies deem the final EIS adequate, PolyMet hopes to finalize the land exchange with the U.S. Forest Service and obtain all required permits in the first half of 2014. That would allow for construction to start in the second half of 2014. Officials say it will take approximately 15 months to develop the mine, refurbish the processing plant, and build a floatation circuit to produce metal concentrates. If the EIS is approved, however, lawsuits are likely, which could slow progress considerably.

Could mining last more than 20 years?

PolyMet has indicated it could expand the project beyond what is described in the environmental impact statement. But the EIS only covers the 20-year plan and is specific about how much area would be mined and how much waste would be generated. If PolyMet wants to expand the mining site or increase its production and waste output, a new environmental study would be conducted to assess the impact of that expansion.

How many jobs would be created?

The project would create 360 full-time jobs, in addition to roughly 1,000 temporary, construction jobs — equal to about 2 million construction hours, the same amount of time required to build Target Field. A University of Minnesota-Duluth study predicts the project will create an additional 600 spin-off jobs.