That's good news that SFMI owes the 15% only on tailings, and not unprocessed ore (I assume both terms refer to the above ground piles). Because, according to the Idaho Geological Survey report (linked here a few times, maybe it could be added to the home page):

“The only mill site in the area with a significant amount of tailings is at the Dewey Mine.” p 19

The piles at the other sites (mostly mine sites, not mill sites) are unprocessed ore. The only sites with true tailings are the few mill sites, and evidently they don't have a lot.