PolyMet water model raises doubts about FEIS

Last week, we reported again on the sharp difference of opinion between the Department of Natural Resources and the Great Lakes Indian Fish and Wildlife Commission, or GLIFWC, about how much untreated mine water would likely escape from the PolyMet mine and where it’s likely to flow. This week, I’m writing to tell you why I think it matters.

Obviously, no one, including the people who actually put the Final Environmental Impact Statement on PolyMet together could possibly have time to understand all aspects of it in detail. For the public, myself included, finding time to read even a portion of it, is daunting.

That’s why I’ve focused my attention on a single issue— groundwater discharge. It’s important, in part, because groundwater is the one type of mine discharge that won’t be treated by whatever wastewater system PolyMet, or anyone else, is likely to install at the NorthMet mine site. Groundwater leakage will likely carry with it contaminants that the treatment is designed to prevent in surface discharges.

And there’s another reason for a singular focus. By drilling down on one topic, you can get a sense of how much real science, versus public relations, there really is in an immense document like the FEIS. One topic can serve as a sampling of the larger whole.

As most folks who’ve followed this issue probably recall, the FEIS put out by the DNR last month predicts that very little groundwater will leave the mine— just ten gallons per minute, and it will flow to the south, i.e. into the St. Louis River watershed. GLIFWC, led by their lead scientist John Coleman strongly disagrees, arguing that hundreds of gallons per minute are likely to escape the mine, and most of that will flow to the north, into the Kawishiwi River watershed.

I’ve talked to Coleman at length, read his detailed submissions to the DNR and would say I probably understand his arguments as well as a non-scientist is likely to. At the same time, I’ve reviewed relevant portions of the FEIS and have received detailed responses from the DNR to a number of related questions that I’ve asked. The agency also declined to answer what I thought were some of the most critical questions of all, and that is troubling by itself.

I’m not a scientist, but that shouldn’t stop anybody from doing their best to inform themselves and draw their own conclusions. And based on my research, I think the DNR is extremely vulnerable on this issue. And I think they know it.

Here’s why:

• The geology of the site clearly supports a northward flow of groundwater. According to the FEIS, virtually the entire pit is encompassed in the Duluth Complex, that zone of sulfide-bearing rock that is the focal point of so much interest. That rock is relatively free of cracks and fissures, which means water doesn’t flow through it very readily. It’s sort of like a big bucket. Water can enter or leave at the surface, but it doesn’t flow in or out much at all at the sides. That’s a good thing if you’re trying to contain the discharge of untreated water.

There is, however, one exception. The north wall of the proposed NorthMet east pit butts up against a different zone of rock, known as the Virginia Formation, and this is what separates the east pit from the Peter Mitchell taconite pit located about 2,000 meters to the north. According to the DNR, the Virginia Formation is more permeable than the Duluth Complex. That means more water can flow through that rock. So our bucket analogy now has a twist. There’s a few very small holes on the north side of our bucket. Ask yourself, which way is the water likely to drain? All things being equal, most water will escape through the north wall of the east pit, and you don’t need a model to tell you that. Water will escape where there is the least resistance— that’s basic physics.

• The volume of flow will be substantially greater if water escapes to the north. The reason the FEIS predicts only minimal loss of groundwater is that it assumes a southward flow into the nearly impermeable Duluth Complex. If, as physics demands, the water escapes through the more permeable Virginia Formation, more mine water will escape treatment. Both models, Coleman’s and the one used in the FEIS, predict that hundreds of gallons per minute, or up to a million gallons per day, will flow through the Virginia Formation between the two pits. The only question is which direction. The FEIS model got the water to theoretically flow south, by assuming that the water elevation in the Peter Mitchell pit was more than three hundred feet higher than it actually will be at closure. DNR officials say the modelers did that intentionally, in order to maximize the model’s estimate of groundwater that would flow into the NorthMet east pit. Doing so would ensure they had adequate capacity to keep the mine dewatered during operations and to treat outflow from the surface after closure.

Water elevations matter, after all. The higher water sits, the more pressure it exerts, which is why we use water towers. If you assume that the water level in the Peter Mitchell pit is substantially higher than at NorthMet, it only makes sense that your model will predict a downhill flow to NorthMet. Coleman’s argument is equally straightforward— set the water levels in your model where they should be, and the results reverse, since, in reality, water levels in the NorthMet pit are expected to be higher than at Peter Mitchell.

The DNR claims that the model can’t be used to demonstrate a northward outflow, but they haven’t been to explain why in any reasonable fashion. When I really pressed them on it, the DNR declined to answer my questions. They either don’t have a credible explanation or they aren’t as interested in transparency as they claim.

• The Peter Mitchell pit and the NorthMet east pit are part of the same groundwater system. Essentially, they’re part of the same watershed, at least underground. The DNR won’t tell you this (I asked them specifically and they declined to answer) but their explanation of their water model is nonsensical otherwise. If the FEIS model suggests that an artificially high water level in the Peter Mitchell pit will push more groundwater into the NorthMet east pit, then the two are hydrologically-connected. If they weren’t, the inflow to NorthMet would be unaffected no matter how high you set the water level in the Peter Mitchell pit.

And if water can flow one way through rock, it can flow the other. It just depends which way is downhill. In the FEIS model, it’s downhill to NorthMet. Set the water levels where they should be, and the flow reverses, heading north.

• The DNR’s suggestion that a groundwater mound might form to block the northward flow of water is pure speculation. It’s also inconsistent with their own model, which suggests hundreds of gallons of minute will flow south from the artificially high Peter Mitchell pit. Are we to believe that the groundwater mound will only form if water flows north, but not south? The degree of groundwater penetration depends on the permeability of the rock that separates the surface from the groundwater aquifer, not on the direction of flow of groundwater. The co-lead agencies appear to be grasping at straws with this explanation.

It’s certainly fair to ask, who cares? Does it matter if a million gallons a day of untreated mine water escapes from NorthMet’s east pit? I don’t know the answer to that question, but I do know one thing— that’s the kind of effect that should have been studied and disclosed as part of the FEIS. It’s the kind of undisclosed effect that could very well upend this process in a federal court.

My take is that politics overrode the science, as is far too common in our society these days. If the DNR acknowledged in their FEIS that a million gallons a day of untreated mine water might escape the NorthMet pit and flow north, eventually into the Kawishiwi River watershed, this project would have been a non-starter politically. So I suspect they let PolyMet and their consultant, Barr Engineering, fudge it, and hoped no one would peer behind the curtain. If their handling of the water modeling is typical of the rest of the FEIS, Minnesotans should be highly skeptical that this is anything other than public relations dressed up as science. After ten years, Minnesotans deserved better.