I talked to my cousin who lives in Casper and works in the largest open pit coal mine in the U.S. He said last Tuesday night it was -29*F on the thermometer with the winds roaring. They cannot walk the big dragline over frozen ground (company policy) - they have to take a dozer, cut the frozen ground away to unfrozen ground, smooth it out then move the dragline. He said that it was so cold that the ground would freeze before they could get it smoothed out. They got it moved, but it wasn't fun.
If you've seen "Monster Machines" on the discovery channel, about half of that was filmed in their mine.
