Complex sentence: Coeur Alaska's Kensington mine (located north of Juneau) had not operated since 1928, and the company required a permit to dispose of up to 4.5 million tons of tailings.
Split into simpler sentences: Coeur Alaska's Kensington mine (located north of Juneau) had not operated since 1928. The company required a permit to dispose of up to 4.5 million tons of tailings.