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Berkeley Pit
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Berkeley Pit
The Berkeley Pit is a former open pit copper mine in the western United States, located in Butte, Montana. It is one mile (1.6 km) long by one-half mile (800 m) wide, with an approximate maximum depth of 1,780 feet (540 m). It is filled to a depth of about 900 feet (270 m) with water that is acidic (4.1 - 4.5 pH level), about the acidity of beer or tomatoes. As a result, the pit's water is laden with heavy metals and dissolved metals that leach from the rock in a natural process known as acid rock drainage. The pit's water content includes (but is not limited to) dissolved copper, arsenic, cadmium, zinc, and sulfuric acid.
The mine was opened in 1955 and operated by the Anaconda Copper Mining Company, and later by the Atlantic Richfield Company (ARCO), until its closure on April 22, 1982. When the pit was closed, the water pumps in the nearby Kelley Mine, 3,800 ft (1,200 m) below the surface, were turned off, and groundwater began to slowly fill the Berkeley Pit, rising at about the rate of one foot (30 cm) per month. Since its closure, the water level in the pit has risen to within 150 feet (46 m) of the "protective water level", above which the polluted water might flow into a nearby creek and other local water sources. As a result, a water treatment plant has been operating at the site since October 2019.
The Berkeley Pit can be visited by tourists, with a viewing stand and small visitor center.
The underground Berkeley Mine was located on a prominent vein extending to the southeast from the main Anaconda vein system (sometimes called "the richest hill on earth"). When open pit mining operations began in July 1955, near the Berkeley Mine shaft, the older mine gave its name to the pit. The open-pit style of mining superseded underground operations because it was far more economical and much less dangerous than underground mining.
Within the first year of operation, the pit extracted 17,000 tons of ore per day at a grade of 0.75% copper. Ultimately, about one billion tons of material were mined from the Berkeley Pit. Copper was the principal metal produced, although other metals were also extracted, including silver and gold.
Many of Butte's original ethnic mining communities including Meaderville, McQueen, East Butte, Dublin Gulch, and Finn Town were consumed by land purchases to expand the pit eastward during the 1970s. The Anaconda Company bought the homes, businesses and schools built over remaining ore deposits. Homes were either destroyed by pit expansion or moved to the southern end of Butte. Although residents were compensated for their acquired property, many thriving ethnic communities were disintegrated.[citation needed]
The Berkeley Pit is located within the Butte Mine Flooding Operable Unit, a part of the Silver Bow Creek/Butte Area Environmental Protection Agency Superfund site. The pit itself was added to the federal Superfund site list in 1987.
The Berkeley Pit is a low spot and acts like a sump for contaminated water. For this reason, it is currently an active part of the remedy for this operable unit. A pilot water treatment project was initiated in 2019. It began treating and releasing Berkeley Pit water into Silver Bow Creek at the confluence with Blacktail Creek. This was done to protect the local groundwater from eventually becoming contaminated by rising pit water. The plant cost $19 million and was designed to treat ten million gallons of water per day.
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Berkeley Pit
The Berkeley Pit is a former open pit copper mine in the western United States, located in Butte, Montana. It is one mile (1.6 km) long by one-half mile (800 m) wide, with an approximate maximum depth of 1,780 feet (540 m). It is filled to a depth of about 900 feet (270 m) with water that is acidic (4.1 - 4.5 pH level), about the acidity of beer or tomatoes. As a result, the pit's water is laden with heavy metals and dissolved metals that leach from the rock in a natural process known as acid rock drainage. The pit's water content includes (but is not limited to) dissolved copper, arsenic, cadmium, zinc, and sulfuric acid.
The mine was opened in 1955 and operated by the Anaconda Copper Mining Company, and later by the Atlantic Richfield Company (ARCO), until its closure on April 22, 1982. When the pit was closed, the water pumps in the nearby Kelley Mine, 3,800 ft (1,200 m) below the surface, were turned off, and groundwater began to slowly fill the Berkeley Pit, rising at about the rate of one foot (30 cm) per month. Since its closure, the water level in the pit has risen to within 150 feet (46 m) of the "protective water level", above which the polluted water might flow into a nearby creek and other local water sources. As a result, a water treatment plant has been operating at the site since October 2019.
The Berkeley Pit can be visited by tourists, with a viewing stand and small visitor center.
The underground Berkeley Mine was located on a prominent vein extending to the southeast from the main Anaconda vein system (sometimes called "the richest hill on earth"). When open pit mining operations began in July 1955, near the Berkeley Mine shaft, the older mine gave its name to the pit. The open-pit style of mining superseded underground operations because it was far more economical and much less dangerous than underground mining.
Within the first year of operation, the pit extracted 17,000 tons of ore per day at a grade of 0.75% copper. Ultimately, about one billion tons of material were mined from the Berkeley Pit. Copper was the principal metal produced, although other metals were also extracted, including silver and gold.
Many of Butte's original ethnic mining communities including Meaderville, McQueen, East Butte, Dublin Gulch, and Finn Town were consumed by land purchases to expand the pit eastward during the 1970s. The Anaconda Company bought the homes, businesses and schools built over remaining ore deposits. Homes were either destroyed by pit expansion or moved to the southern end of Butte. Although residents were compensated for their acquired property, many thriving ethnic communities were disintegrated.[citation needed]
The Berkeley Pit is located within the Butte Mine Flooding Operable Unit, a part of the Silver Bow Creek/Butte Area Environmental Protection Agency Superfund site. The pit itself was added to the federal Superfund site list in 1987.
The Berkeley Pit is a low spot and acts like a sump for contaminated water. For this reason, it is currently an active part of the remedy for this operable unit. A pilot water treatment project was initiated in 2019. It began treating and releasing Berkeley Pit water into Silver Bow Creek at the confluence with Blacktail Creek. This was done to protect the local groundwater from eventually becoming contaminated by rising pit water. The plant cost $19 million and was designed to treat ten million gallons of water per day.
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