starwatcher wrote on Dec 12^th, 2009 at 5:55pm:

The Polymet site is using the former LTV iron mining site, their mine development is farther away from the BWCA that the existing taconite operations, and it isn't even in the same drainage basin.  The water flows toward the St. Louis River and the BWCA / Quetico is on the other side of the continental divide.

I wasn't sure that was correct at first, but you're right. Excellent point. The Mesabi Range separates the St. Louis River drainage (#3 on DNR map below) from the Little Fork River (#76), the Vermillion River (#73), and the Rainy River (#72) basins. This contact also forms the Northern Continental Divide.

So, a contamination event at the NorthMet project sites won't affect the BWCA or Quetico waters... but it could potentially affect the waters of Lake Superior.

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kypaddler wrote on Dec 11^th, 2009 at 9:38pm:

p.s. On the underground vs. surface issue. A dumb question for my own edification: Is it much cheaper and much safer to come at the mineral from above ground, i.e. digging a pit?

It depends on the operation. These deposits are actually kind of low-grade, but they're big, and some of them like the NorthMet are pretty shallow. In this case, a bulk-tonnage earth-moving operation is the cheapest and most efficient way to get the ore from the ground to the processing plant. In other cases, where the ore targets are smaller, deeper, higher grade, etc., an underground approach would be the best bet. It really depends on a lot of different factors.