The Berkeley Pit is a former

open pit Open-pit mining, also known as open-cast or open-cut mining and in larger contexts mega-mining, is a surface mining technique of extracting rock or minerals from the earth from an open-air pit, sometimes known as a borrow. This form of mining ...

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish ...

mine in the

western Western may refer to: Places *Western, Nebraska, a village in the US * Western, New York, a town in the US *Western Creek, Tasmania, a locality in Australia *Western Junction, Tasmania, a locality in Australia *Western world, countries that i ...

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...

, located in

Butte, Montana Butte ( ) is a consolidated city-county and the county seat of Silver Bow County, Montana, United States. In 1977, the city and county governments consolidated to form the sole entity of Butte-Silver Bow. The city covers , and, according to th ...

. It is long by wide, with an approximate depth of . It is filled to a depth of about with water that is heavily

acidic In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a s ...

(2.5

pH level In chemistry, pH (), historically denoting "potential of hydrogen" (or "power of hydrogen"), is a scale used to specify the acidity or basicity of an aqueous solution. Acidic solutions (solutions with higher concentrations of ions) are ...

), about the acidity of

Coca-Cola Coca-Cola, or Coke, is a carbonated soft drink manufactured by the Coca-Cola Company. Originally marketed as a temperance drink and intended as a patent medicine, it was invented in the late 19th century by John Stith Pemberton in Atla ...

, lemon juice,Edwin Dobb. "New Life in a Death Trap". ''Discover'', 2000. or

gastric acid Gastric acid, gastric juice, or stomach acid is a digestive fluid formed within the stomach lining. With a pH between 1 and 3, gastric acid plays a key role in digestion of proteins by activating digestive enzymes, which together break down the ...

. As a result, the pit is laden with

heavy metals upright=1.2, Crystals of lead.html" ;"title="osmium, a heavy metal nearly twice as dense as lead">osmium, a heavy metal nearly twice as dense as lead Heavy metals are generally defined as metals with relatively high density, densities, atomi ...

and dangerous chemicals that leach from the rock, including copper,

arsenic Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, bu ...

cadmium Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...

zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic t ...

, 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 ( ) is a brand of gasoline stations currently owned by Marathon Petroleum after BP sold its rights. BP commercializes the brand in Northern California, Oregon and Washington, while Marathon has rights for the rest of the United States an ...

(ARCO), until its closure on Earth Day in 1982. When the pit was closed, the water pumps in the nearby Kelley Mine, below the surface, were turned off, and

groundwater Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidat ...

from the surrounding aquifers 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 natural

water table The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water. It can also be simply explained as the depth below which the ground is saturated. Th ...

. The Berkeley Pit is currently one of the largest

Superfund Superfund is a United States federal environmental remediation program established by the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA). The program is administered by the Environmental Protection Agen ...

sites. The water, with dissolved oxygen, allows

pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Fe S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic luster and pale brass-yellow hue giv ...

and

sulfide mineral The sulfide minerals are a class of minerals containing sulfide (S2−) or disulfide (S22−) as the major anion. Some sulfide minerals are economically important as metal ores. The sulfide class also includes the selenides, the tellurides ...

s in the ore and wall rocks to decay, releasing acid. The acidic water in the pit carries a heavy load of dissolved heavy metals. A water treatment plant has been operating since October 2019. The Berkeley Pit is a tourist attraction, with an adjacent gift shop. An admission fee is charged to go out on the viewing platform.

History

The underground Berkeley Mine was located on a prominent

vein Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenate ...

extending to the southeast from the main Anaconda vein system. When

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 1,000,000,000 tons of material were mined from the Berkeley Pit. Copper was the principal metal produced, although other metals were also extracted, including

silver Silver is a chemical element with the Symbol (chemistry), symbol Ag (from the Latin ', derived from the Proto-Indo-European wikt:Reconstruction:Proto-Indo-European/h₂erǵ-, ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, whi ...

and

gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile ...

. Two communities and much of Butte's previously crowded east side were consumed by land purchases to expand the pit during the 1970s. The Anaconda Company bought the homes, businesses and schools of the working-class communities of Meaderville, East Butte, and McQueen, east of the pit site. Many of these homes were either destroyed, buried, or moved to the southern end of Butte. Residents were compensated at market value for their acquired property.

Pollution, toxicity, and cleanup

The Berkeley Pit is a part of the Silver Bow Creek/Butte Area

Environmental Protection Agency A biophysical environment is a biotic and abiotic surrounding of an organism or population, and consequently includes the factors that have an influence in their survival, development, and evolution. A biophysical environment can vary in scale f ...

site, considered one of the largest in America, and the pit itself was added to the federal Superfund site list in 1987. It is one of sixteen Superfund sites in Montana, and the Berkeley Pit is the final unrestored section of the Silver Bow Creek/Butte Area site. In 1995, a flock of migrating

geese A goose ( : geese) is a bird of any of several waterfowl species in the family Anatidae. This group comprises the genera ''Anser'' (the grey geese and white geese) and '' Branta'' (the black geese). Some other birds, mostly related to the she ...

landed in the Berkeley Pit and died. A total of 342 carcasses were recovered.

ARCO ARCO ( ) is a brand of gasoline stations currently owned by Marathon Petroleum after BP sold its rights. BP commercializes the brand in Northern California, Oregon and Washington, while Marathon has rights for the rest of the United States an ...

, the custodian of the pit, denied that the toxic water caused the death of the geese, attributing the deaths to an acute

aspergillosis Aspergillosis is a fungal infection of usually the lungs, caused by the genus '' Aspergillus'', a common mould that is breathed in frequently from the air around, but does not usually affect most people. It generally occurs in people with lung di ...

infection that may have been caused by a grain fungus, as substantiated by Colorado State University

necropsy An autopsy (post-mortem examination, obduction, necropsy, or autopsia cadaverum) is a surgical procedure that consists of a thorough Physical examination, examination of a Cadaver, corpse by dissection to determine the cause, mode, and manner o ...

findings. These findings were disputed by the State of Montana on the basis of its own lab tests. Necropsies showed their insides were lined with burns and festering sores from exposure to high concentrations of copper, cadmium, and arsenic. (Levels of copper are high enough that Montana Resources has mined copper directly from the water.) On November 28, 2016, several thousand snow geese died after a large flock landed in the pit's water to avoid a snowstorm. Immediately after the event, officials made efforts to scare birds away and prevent more from landing in the area. An official report issued in 2017 by the U.S. Fish and Wildlife Service found that the 3,000 to 4,000 snow geese that died at the Berkeley Pit were killed by exposure to sulfuric acid and heavy metals. The Berkeley Pit started utilizing Phoenix Wailers, which have been effective in deterring birds from landing at or staying in Berkeley Pit for an extended period of time. (A Wailer is a machine that causes birds to move away from airport runways and helipads, using high fidelity natural sounds such as distress calls, alarm calls and cries of predators.) Studies have shown that the Wailers have been effective in limiting bird deaths in most cases, but they have not worked as well when faced with a large number of birds. Staff also use firearms to scare away birds during spring migration seasons. Construction began on a treatment plant at the Berkeley Pit in 2018, to treat water in the Pit before it would contaminate local

. The treatment facility will be able to treat ten million gallons of water per day. Construction of the $19 million facility was completed in August 2019 and the first discharge of treated water into a local creek happened in October 2019.

Important dates

*1994 – September, 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, USEPA 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) – USEPA 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.

Geography

The mine is at , at an altitude of 4,698 feet (1432 m) above mean sea level.

Geology

The Butte mining district is characterized by the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...

Boulder

batholith A batholith () is a large mass of intrusive igneous rock (also called plutonic rock), larger than in area, that forms from cooled magma deep in Earth's crust. Batholiths are almost always made mostly of felsic or intermediate rock types, su ...

which

metamorphosed Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock (protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, causi ...

surrounding rocks during the

Laramide orogeny The Laramide orogeny was a time period of mountain building in western North America, which started in the Late Cretaceous, 70 to 80 million years ago, and ended 35 to 55 million years ago. The exact duration and ages of beginning and end of the o ...

. Ore formation occurred with the

intrusion In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...

of the Butte

quartz Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical ...

monzonite Monzonite is an igneous intrusive rock, formed by slow cooling of underground magma that has a moderate silica content and is enriched in alkali metal oxides. Monzonite is composed mostly of plagioclase and alkali feldspar. Syenodiorite is an ob ...

pluton In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...

. Mining of

sulfide minerals The sulfide minerals are a class of minerals containing sulfide (S2−) or disulfide (S22−) as the major anion. Some sulfide minerals are economically important as metal ores. The sulfide class also includes the selenides, the tellurides, t ...

began in the district in 1864. Placer deposits were mined out by 1867. Silver

lode In geology, a lode is a deposit of metalliferous ore that fills or is embedded in a fissure (or crack) in a rock formation or a vein of ore that is deposited or embedded between layers of rock. The current meaning (ore vein) dates from the ...

s were then the most productive until copper was discovered in 1881.

Open-pit mining Open-pit mining, also known as open-cast or open-cut mining and in larger contexts mega-mining, is a surface mining technique of extracting rock or minerals from the earth from an open-air pit, sometimes known as a borrow. This form of min ...

started in 1955.

Copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish ...

has historically been the main metal produced, though

lead Lead is a chemical element with the Symbol (chemistry), symbol Pb (from the Latin ) and atomic number 82. It is a heavy metals, heavy metal that is density, denser than most common materials. Lead is Mohs scale of mineral hardness#Intermediate ...

manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy u ...

and

have been produced at various times. File:Butte Cross Section.PNG, Geologic cross section File:Butte District Geology.PNG, Butte District

geologic map A geologic map or geological map is a special-purpose map made to show various geological features. Rock units or geologic strata are shown by color or symbols. Bedding planes and structural features such as faults, folds, are shown with str ...

File:Butte Mineral Zones.PNG, Mineral zones

Organisms in the water

A protozoan species, ''

Euglena ''Euglena'' is a genus of single cell flagellate eukaryotes. It is the best known and most widely studied member of the class Euglenoidea, a diverse group containing some 54 genera and at least 200 species. Species of ''Euglena'' are found in f ...

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.

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.

References

External links

Berkeley Pit Photos from the Montana Department of Environmental QualityPitWatchISS 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 Nov 2013 *{{HAER , survey=MT-36-D , id=mt0098 , title=Butte Mineyards, Berkeley Pit, Butte, Silver Bow County, MT , photos=3 , color=1 , cap=2 , link=no 1955 establishments in Montana 1983 establishments in Montana Anaconda Copper Butte, Montana Copper mines in the United States Environmental disasters in the United States Historic American Engineering Record in Montana History of Montana Geography of Silver Bow County, Montana Geology of Montana Mines in Montana Open-pit mines Superfund sites in Montana Surface mines in the United States Tourist attractions in Butte, Montana