MONTANA Skyrocketing electricity prices in Montana are indirectly raising the level of Butte’s Berkeley Pit, a 900-foot-deep, 30 billion-gallon soup of acid-mine runoff that ranks as the nation’s largest Superfund site. In mid-July, copper-mining company Montana Resources suddenly halted its Butte operations, blaming high electrical rates for the shutdown. During normal operations, the mine is […]