KENNECOTT LEACH AND FLOTATION FACILITY —
The ammonia leach flotation process was pioneered in this building at the historic Kennecott Copper Mine. Modern mines use cyanide instead.
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The mine and the towns of Kennecott and nearby McCarthy were all located within what is now Wrangell St-Elias National Park. Kennecott (a misspelling of the nearby Kennicott Glacier) consisted of mining infrastructure (mill, flotation plant, crushers, etc.) as well as a town for the miners and their families. The ore came from five separate mines up in the hills to the NE: Erie Mine, Jumbo Mine, Bonanza Mine, Mother Lode Mine, and Glacier Mine. A system of tramways moved ore between the sites and the town. At its peak the town had around 300 people, and an additional 200-300 miners lived at the mines. Much of the infrastructure still remains and the town of Kennecott has become a tourist destination within the park.
Comparison to Pebble Mine
The Kennecott mine had relatively few long-term environmental impacts for a mine of its size, and has been used by supporters of the proposed Pebble Mine as an example to follow. However, there are significant differences between the two sites.
Acid Mine Drainage
…Acid mine drainage is a major problem with many hardrock mines, including almost all mines where the metal ore is bound up with sulfur (metal sulfide mines)…
The copper deposit mined by Kennecott was very high grade and the copper sulfides were found in conjunction with carbonate minerals. These carbonate minerals reacted to neutralize acid mine drainage. The high grade of copper (average 13%) meant that relatively little waste was produced by the mine, especially since much of the rich ore was removed selectively by pickaxe. In contrast, the deposit at the proposed Pebble Mine is 2000 times the volume, doesn’t contain significant acid neutralization potential (i.e. carbonate minerals), and the average copper grade is only 0.34%.
Additionally, the Kennecott mine is situated in a setting where the deposit is rapidly eroding, so downstream waters are already exposed to the mineral material, and downstream ecosystems are adapted to sediment and runoff from the mined area. In contrast, the Pebble deposit is buried under surficial sediment in an area that is eroding very little, and so is insulated from the environment if no mining occurs.
Created: Jan. 19, 2018