db wrote on Jan 30^th, 2010 at 6:48am:


I'll just say that mining has legacy issues just like other industries previous to the environmental movement in the 70's and the National Environmental Policy Act.  Environmental regulators are very much aware of sulfide mining potential for acid mine drainage and recent reclamation activities involve making sure that any waste rock is managed so that limestone is used to neutrallize its potential to become acidic.  This has been successfully demonstrated.  The other legacy from sulfide ores are from smelter operations like Sudbury Ontario and still in use thoughout the world, in Russia and China.  The new cutting edge hydro process for PolyMet uses an autoclave and sulfide ore as the fuel instead of smelting the ore.  

starwatcher

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I'm having trouble with the DNR website at the moment, so I can't point to any specifics right now, but the underground water was evaluated in the Draft EIS. De-watering the pits would lower the local water table a little bit, and it could stay that way for 65 years. This and other factors could lower the flow in the Partridge River by as much as 9%, which they say shouldn't be enough to cause "significant" changes in the stream's morphology.

As a protective measure, a network of monitoring wells would be drilled in the areas adjacent to the site, especially down-gradient or in the general direction of subsurface flow. If these monitoring wells show a negative change in the chemistry of the subsurface water (which is supposed to be prevented by the multiple-layer liner systems in the pit itself), then a network of drawing wells will be activated to remove as much of the contaminated water from the aquifer as possible.

The liner system, along with the flooding of the pits to cover the waste rock, is in itself a pretty good way to handle the tailings. The sulfide minerals need to be exposed to air to develop sulfuric acid, so while underwater, they are *practically* inert. Simple lime treatments can also help control pH levels within the flooded pit and surrounding area. Also, it seems like one of the points of concern, aside from the sulfide-bearing minerals in the ore rock, is the sulfide-bearing sediments of the Virginia Formation, which would be exposed as the pit was excavated. This part would also be lime-treated and lined, to prevent any further acid formation.

But it should be noted that the Virginia Formation, and other rock units containing even greater concentrations of sulfides, are already exposed at the surface naturally in many other places across NE Minnesota - each contributing its own small amount of naturally-occurring weak acid runoff to the areas around it.

And generally speaking, in these hardrock areas, groundwater flow is very slow. So if a problem were to arise with the liner systems, a serious problem can most likely be avoided by the monitoring + drawing well network. These wells are a pretty standard thing, that part isn't exactly new technology.



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If I have it right, the "new technology" refers to systems on the processing end, not the extraction end. So this would be a cause for concern at the plant site, not the mine site. We can expect many safety measures to be in place with regards to the handling of waste / slurry material, and the "new technology" would probably create a waste stream that is less toxic / reactive than other systems in use at other processing sites. But I haven't had a chance to look into this part yet, so don't quote me on that.



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According to the State's Pollution Control Agency, most of the mercury deposited in Minnesota's waterways comes from the air, and 90% of that comes from other states and countries. Of the 10% of the total mercury deposited here that originates here, 21% of that comes from taconite processing - making up 2.1% of the total mercury found in our lakes, rivers, and fish. Burning coal and the use / disposal of products containing mercury are by far the largest contributors.

See (You need to Login or Register to view media files and links) for further details.


I want to again stress the fact that I am still up in the air about this project. But I am trying to add facts to the discussion as much as I can.

Looks like I responded at about the same time as AK.

WR,

They are ten miles away from the divide and thirty miles from the BWCAW.  All the experts and environmental agencies weighed in on it, reviewed the EIS and didn't flag it; you could be right, but it seems like a long distance to impact on groundwater.  

starwatcher

starwatcher wrote on Jan 30^th, 2010 at 9:08pm:


I have seen and know how "think tanks" and "group think" work. Another longshot was the space shuttle Challenger in January of 1986. Two engineers at Morton Thiokol held out but finally nuckled under pressure from the others in the end......that long shot cost us seven human lives and a couple billion worth of spacecraft. Three months later, another long shot now known as Chernobyl took place. Ya, 24 years have passed but the history books show that we never seem to learn from history. Don't test the "new technology" in an area where the cost of failure is very high. Try it and prove it elsewhere. The aquifers in that area are to valuable for an "experiment" in new technology.

WR