Berkeley Pit
Berkeley pit is a former open pit copper mine on the northeastern edge of the US city of Butte in the state of Montana . The open pit , which was built in the course of mining since 1881 from 1955, is 1,600 m long, 800 m wide and 540 m deep and filled with 120 million cubic meters of sulfuric acid water ( pH value = 2.5). The water contains a large amount of dissolved heavy metals and other dissolved substances, including arsenic , cadmium , zinc and sulfuric acid .
The copper mining stopped in 1982.
history
From 1881 to 1947 94,900 tonnes of copper in the Anaconda Copper Mine from Anaconda Copper in civil engineering dismantled. From 1955, the Berkeley pit opencast mine was opened on the site by the Atlantic Richfield Company . In 1977 Anaconda Copper was bought by the Atlantic Richfield Company (ARCO). In 1982, the open pit was closed down . The ore was smelted in Anaconda (Montana), 40 kilometers north-west .
After the mine was closed, the pumps were removed and the pit filled with groundwater .
Environmental impact
The biggest problem is the existing pyrite (FeS 2 ). This sulfur mineral ("copper pebbles") reacts with the low-oxygen water under the action of microorganisms to form sulfuric acid. Heavy metals in the rock dissolve in acidic water. Water with a high acid content can dissolve many more heavy metals than water with a neutral pH (pH 7). The current copper content of the water is around 187 ppm .
In 1995, 324 snow geese died from contaminated acidic water. ARCO dismissed this as a bacterial disease. Since then, an observation center has tried to protect the birds. Among other things, they are scared off with rifle shots and there are also automatic alarm systems. This works well for certain bird species like ducks and geese , but not for other birds. Waterfowl often go into hiding when there is danger. The birds do not die immediately, but 4 to 6 hours of exposure to the water create a lethal limit.
In December 2016, a large flock of wild geese landed on the water fleeing a snow storm. Thousands of wild geese died within hours.
The locals fear the exhaust gases that rise from the pit.
Redevelopment
There have been some attempts to rehabilitate the pit, but the acid content has remained very high. A complete renovation would require funds that no one wants to raise. Moreover, opinions are divided as to who would be responsible for the redevelopment. ARCO's job would be according to the polluter pays principle , but the company evades this responsibility. The state of Montana doesn't want to invest because it believes ARCO is responsible. The necessary strict measures are now to be financed from federal funds for environmental disasters .
Web links
Individual evidence
Coordinates: 46 ° 1 ′ 2 " N , 112 ° 30 ′ 37" W.