Berkeley Pit

The Berkeley Pit is a former open pit copper mine in the western United States, located in Butte, Montana. It is long by wide, with an approximate maximum depth of . It is filled to a depth of about 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, below the surface, were turned off, and groundwater began to slowly fill the Berkeley Pit, rising at about the rate of per month. Since its closure, the water level in the pit has risen to within 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 Berkeley Pit is a former open pit copper mine in the western United States, located in Butte, Montana. It is long by wide, with an approximate maximum depth of . It is filled to a depth of about 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, below the surface, were turned off, and groundwater began to slowly fill the Berkeley Pit, rising at about the rate of per month. Since its closure, the water level in the pit has risen to within 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. ==History== 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 considered more economical and less dangerous to workers 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 Finntown 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 to some extent for their acquired property, many thriving ethnic communities were lost. ===Protozoans=== A protozoan species, Euglena mutabilis, was found to reside in the pit by Andrea A. Stierle and Donald B. Stierle, and the protozoans have been found to have adapted to the harsh conditions of the water. Intense competition for the limited resources caused these species to evolve the production of highly toxic compounds to improve survivability. Natural products such as berkeleydione, berkeleytrione, and berkelic acid have been isolated from these organisms which show selective activity against cancer cell lines. Some of these species ingest metals and are being investigated as an alternative means of cleaning the water. ===Important dates=== 1994 – September, U.S. Environmental Protection Agency (EPA)/DEQ issue Record of Decision (ROD) for Butte Mine Flooding Operable Unit. 1996 – April, Montana Resources (MR) and ARCO divert Horseshoe Bend (HSB) drainage water away from Berkeley Pit to slow filling rate, per ROD. 2000 – July, MR suspends mining operations due to high energy costs; HSB water allowed to flow back into pit, increasing pit filling rate. 2002 – March, US EPA and Montana Department of Environmental Quality (MDEQ) enter into a Consent Decree with BP/ARCO and the Montana Resources Group (known as the Settling Defendants) for settlement of past and future costs for this site. 2002 (mid/late) – US EPA and MDEQ issue order for Settling Defendants to begin design of water treatment plant for HSB water. Settling Defendants issue contract and begin construction of treatment plant. 2003 – November, MR resumes mining operations. 2003 – November 17, HSB water treatment plant comes on line slowing pit filling rate. ==Geology== The mine is at an altitude of 4,698 feet (1432 m) above mean sea level. According to the Record of Decision, the pit water level is not to exceed 5,410 feet above sea level. The Butte mining district is characterized by the Late Cretaceous boulder batholith which metamorphosed surrounding rocks during the Laramide orogeny. Ore formation occurred with the intrusion of the Butte quartz monzonite pluton. Mining of sulfide minerals began in the district in 1864. Placer deposits were mined out by 1867. Silver vein lodes were then the most productive until copper was discovered in 1881. Open-pit mining started in 1955. Copper has historically been the main metal produced, though lead, zinc, manganese, silver and gold have been produced at various times. File:Butte Cross Section.PNG|Geologic cross section File:Butte District Geology.PNG|Butte District geological map File:Butte Mineral Zones.PNG|Mineral zones ==Photos== File:BerkeleyPit2.jpg|The Berkeley Pit mine in Butte Montana. File:BerkeleyPit3.jpg|The Berkeley Pit mine in Butte Montana. File:BerkeleyPit4.jpg|The Berkeley Pit mine in Butte Montana. ==See also== Auditor (dog) Chemocline Dark Money List of Superfund sites in Montana Water pollution in the United States Bingham Canyon Mine (in Utah) ==References== ==Further reading== ==External links== Berkeley Pit Photos from the Montana Department of Environmental Quality PitWatch ISS image of Berkeley Pit (dated August 2, 2006) Butte, Montana toxic waste site turned tourist attraction yielding compounds that may be medically, environmentally useful "Casualties of Copper: The Berkeley Pit, Montana." Sometimes Interesting. 20 November 2013

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