“Potash had been mined from Bonneville since the early 1900s, but it wasn’t until the 1990s that the Bureau of Land Management, tasked with overseeing public lands including the Bonneville Salt Flats, determined that potash mining “may be causing the salt layer to thin and retract” and that ‘such diminshment would degrade the unique geology and historical relevance of the site and would disrupt the recreational opportunities that have been part of the BSF for over 80 years.’”