I would say the coal mines that are still active have been overall positive and have fairly robust environmental programs. There are however, numerous old coal mine shafts that were abandoned (and these are pretty old) which have been placed under the Abandoned Mine Lands Division of Public Service Commission. I have no knowledge on the plans for eventual decommissioning of the active mines themselves. I believe the AML stuff is funded by a federal tax on coal production. As coal production decreases in the future, that may shift the financial burden elsewhere, because I'm not sure it's building a trust fund capable of handling future mine closures.
And, of course, there are a fair number of acres now in the area north of Highway 83 causeway between Sak and Audubon that are the remnants of surface mining of coal. I don't know the history on that and why it was left in the form it is currently, but it's now a WMA. Fritz may know a bit more on this topic.
Of course, the above is a bit different in the sense that the coal mines are quite large and are actively mining. This topic is on an industrial processing facility. To compare apples to apples, I would think some of the wastelands created by the oil service companies up on the north side of Williston would be a bit more appropriate. In particular, when I was going to school up there, someone came to the professor who taught some hazardous materials/waste/environmental courses and asked us to look at a parcel of land he was thinking about buying for a DOLLAR from the city. It was an old oilfield tubing and drill pipe cleaning location. The company that owned it went out of business and the city eventually obtained it through forfeiture on property tax delinquency. The guy wanted to use it as a pasture for his horses. Bottom line, we found a number of underground storage tanks that were filled with used and new solvents, piles of scale that was cleaned off of pipe, stacks of old barrels that were a mixture of full of unknown chems, or rusted out and empty.
The environmental liability of obtaining that chunk of land (probably less than 10 acres) was staggering. Scale piles from drill pipe tend to be radiologically contaminated, and the presence of unmonitored and possibly leaking underground and above ground storage tanks and old barrels of solvents could have easily bankrupted the guy.
Not sure whatever happened to that parcel of land, but I am guessing someone eventually just bladed it flat and put it back into an industrial use. I'd still consider the place a not-worth-the-risk of owning, regardless of the asking price.
Like I've suggested before, I am not necessarily opposed to this project at face value, but there's a reason it's being proposed in ND.