Skull valley is bordered to the east by the Stansbury mountains and to the west by the Cedar mountains.
Since this area is deemed to be undesirable for farming or ranching or development... 
well we can't just can't let it sit there, so it's used for societies undesirable stuff.
Nuclear waste, impoverished Indian reservations, chemical weapon burn plants, and  bombing ranges have all combined to make this a "useful" area.