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Berkeley Pit

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Projects > Mines

The Berkeley Pit was an open-pit copper mine located in southwestern Montana, near the city of Butte. However, it was abandoned in 1982 and has since become a toxic pit full of highly contaminated water.

The water is a highly acidic mixture of dangerous chemicals, including arsenic, zinc and sulfuric acid. It also contains a high concentration of dissolved metals, including aluminum, cadmium, and lead. The water currently has a pH of 2.5.[1]

The Berkeley mine operated for 27 years, during which time it produced more than 1 billion tons of ore including copper, lead, zinc, gold and manganese. For some time it was the largest truck-operated open pit copper mine in all of the United States. This resulted in it being nicknamed “The Richest Hill on Earth.”[2]

After the mine’s closure and subsequent flooding, copper continued to be extracted by filtering the contaminated water at a rate of 400,000 pounds (181,437 kg) per month.[3]

Berkeley Pit was originally operated by Anaconda Mining Co. until it was purchased by Atlantic Richfield Co. (ARCO) in 1977. The entire mine complex was 1.5 miles (2.4 km) east to west, and one mile (1.6 km) north to south.[4] The total depth of the pit from the bottom to the highest rim is 1,780 feet (534 m).[5]

Contents

[edit] History

[edit] Origins

During the 1800s, Butte, Montana’s underground mines produced approximately 25 percent of the world’s copper.[6] During World War II, it produced nearly 80 percent.[7] By 1945, it had proven to be a wealth of minerals.

In 1947, Anaconda Mining Co. began its “Greater Butte Project”, where geologists discovered most of the mineral reserve was of a lower grade than originally thought, but close enough to the surface to be mined by open-pit methods.

Open-pit mines were more economical because even low-grade material could be recovered with shovels and trucks. It was also considered significantly less dangerous than underground mining.

The Berkeley Pit Mine was officially opened in March 1955. It began as a small test pit, but by the early 1960s it had become the largest truck-operated open-pit mining operation in the United States.[8]

A number of Butte communities were soon overrun by the site, namely the towns of Meaderville and McQueen, as Anaconda Mining purchased homes, businesses, and schools surrounding the mine.

[edit] New Owners, Abandonment, and Flooding

In 1977, the mine was purchased by Atlantic Richfield Co. (ARCO).

Five years later, ARCO abandoned the mine, shutting down the water pumping stations behind them. These stations were designed to prevent groundwater leaching in and filling the shafts. They were essential to the success and safety of the mine.

Without pumps, the pit filled with surface runoff and groundwater. By 1983, the water level rose more than 1,300 feet (390 m), filling the mine shafts and reaching the bottom of the pit.[9] This water became highly acidic and contained high concentrations of dissolved heavy metals. As the water level increased, so did its pH level.[10]

The level of acidity was caused by the high sulfur content in the surrounding rock. The sulfur reacted with the air and water to become sulfuric acid. Then as the acidic water flowed through the mine, it ate away at the metals contained in the rock and dissolved them into the water. The water then contained the chemicals arsenic, zinc, and sulfuric acid and the metals aluminum, cadmium, and lead.

Following the flooding of Berkeley Pit, the Butte Mine Flooding monitoring network was established. It was made up of the Montana Bureau of Mines and Geology, Montana Resources, and ARCO. Its job was to prevent any contaminated water from reaching nearby aquifiers or surface waters. For this purpose, it utilized 85 ground water monitoring sites, nine continuous water level recorders, and three surface water-gauging stations.[11] All the information collected from these monitoring stations was recorded in a database maintained by the network. The database contained over 2,000 complete water-quality analyses collected semi-annually.[12]

[edit] Record of Decision and Water Treatment Plant

In September 1994, the Environmental Protection Agency (EPA) and Montana Department of Environmental Quality (DEQ) issued a Record of Decision (ROD), a legal document summarizing the science behind the cleanup of the Berkeley Pit. It also established the critical water level: 5,410 feet (1,600 m).

The ROD stipulates that ARCO & Montana Resources must begin pumping and treating the pit water once it reaches the critical level. If not, both will be fined US$25,000 per day.[13] It is estimated the critical level will be reached between 2018[14] and 2021[15]. The date is dependent upon water flow into the pit. If the flow rate is reduced the date will be delayed, but if flow increases the date will be sooner.

In 1996, water was diverted away from the Berkeley Pit, reducing the fill rate by as much as 3,000 gallons (11,356 L) per minute.

In 1998, water was pumped out of the pit to recover the copper mixed within. The copper-rich water was pumped over scrap iron, where it solidified as sludge. Iron replaced the copper; thus the total volume of pit water would neither increase nor decrease. Montana Resources claims to have extracted approximately 400,000 pounds (181,437 kg) of copper per month by filtering the water.[16]

On June 30, 2000, water diversion was postponed. Meanwhile, ARCO & Montana Resources began designing a water treatment facility.

As of March 2002, ARCO and Montana Resources were ordered to pay US$87 million for the cleanup of the Berkeley Pit.[17] This money was intended to fund the construction of a US$20 million[18] treatment facility as well as pay for the ongoing management and operation of the plant.

The Horseshoe Bend Water Treatment Plant opened on November 17, 2003. Diversion soon recommenced. The treatment facility uses lime to reduce the acidity of the pit water. Treated water is used for future mining operations or pumped into a local storm drain.

As of early 2008, performance tests indicated the treatment facility was meeting all discharge standards.

Throughout the entire lifespan of the Berkeley Pit Mine, approximately 320 million tons of ore and 700 million tons of waste rock has been mined.[19] It has produced enough copper to pave a four-lane highway, four inches (10.2 cm) thick from Butte, Montana to Salt Lake City, Utah and 30 miles (48.3 km) further.[20]

The Berkeley Pit mine has generated at least US$48 billion in mineral wealth.

It is now a tourist attraction, charging visitors to gaze upon the lake from a viewing platform.

[edit] Consequences

As a highly toxic lake, the Berkeley Pit is the largest body of contaminated water in the United States.[21] It is also an environmental Superfund site, which the EPA describes as “an uncontrolled or abandoned place where hazardous waste is located, possibly affecting local ecosystems or people.”[22]

The most visible detrimental effect of the lake occurred in 1995, when 342 snow geese landed on the pit, drank from the water, and died.[23]

The water treatment facility was established in 2003 to help deal with the problem, but many environmentalists view it as simply “the best of a series of undesirable choices.”[24]

"The magnitude of the problem is so enormous, the best we can do is figure out an OK Band-Aid, and that's what this is," said Tracy Stone-Manning, executive director of the Clark Fork Coalition, a watchdog group that looks out for the Montana River.[25]

"It's a stunning thing. At this point, we do not know how to detoxify the Berkeley Pit," Stone-Manning said. "We do not know how to make the threat of that pit go away, except to pump and treat that water forever."[26]

However, some scientists believe allowing the water to rise to maximum critical level will eventually lower the water’s acid and metal content by reducing the amount of sulfur bearing rock exposed to the air.[27]

"That may improve water quality and make it cheaper to treat the water when the time comes.”[28]

Meanwhile, scientists have researched the pit and discovered a number of single-celled organisms living in it. Despite the water being 10,000 times more acidic than normal, a chemist named William Chatham found a small vegetative clump floating on the surface of the toxic lake.[29] Since then, scientists have isolated at least 142 different kinds of organisms, including algae, bacteria, protozoans, and fungi.[30]

Two scientists, Andrea and Don Stierle, are currently searching for sources of anticancer, antifungal, and antibacterial agents. They believe some pit microbes may be capable of producing compounds with potential pharmaceutical uses.

“Early tests indicate that some of those organisms may help produce the next generation of cancer drugs.”[31]

However, Andrea Stierle is quick to clarify that even if the test results were independently replicated, it would be years before any drugs could be replicated.[32] The Steirle’s are currently negotiating privately with pharmaceutical companies testing some of the compounds they have discovered, with the hopes of possibly turning them into new drugs.

Other researchers hope these organisms will aid in cleaning up the “toxic stew.”[33]

[edit] Equipment Used

[edit] References

  1. Berkeley Pit: History, 2008-09-24.
  2. Berkeley Pit: History, 2008-09-24.
  3. Tanner, Adam. Montana faces eternal clean-up of toxic lake. The Mining News, September, 2005. (accessed: 2008-09-24)
  4. Berkeley Pit: History, 2008-09-24.
  5. Berkeley Pit. MontanaKids.com, 2008-09-24.
  6. Benson, Rod. Where did the water in the Berkeley Pit come from?. ForMontana.com, 2008-09-24.
  7. Berkeley Pit Superfund Site. The Car Wash Guys, 2008-09-24.
  8. Jenkins, Robert E.; Lorengo, Jerry A. Butte, Montana: The Mines. BNET, January/February 2002. (accessed: 2008-09-24)
  9. Berkeley Pit and BMF Operable Unit. MBMG, 2008-09-24.
  10. Berkeley Pit and BMF Operable Unit. MBMG, 2008-09-24.
  11. Berkeley Pit: History, 2008-09-24.
  12. Berkeley Pit and BMF Operable Unit. MBMG, 2008-09-24.
  13. Berkeley Pit. MontanaKids.com, 2008-09-24.
  14. Butte Berkeley Pit Copper Mine. Sprol.com, June, 2005. (accessed: 2008-09-24)
  15. Official PitWatch website
  16. Tanner, Adam. Montana faces eternal clean-up of toxic lake. The Mining News, September, 2005. (accessed: 2008-09-24)
  17. United States and Montana Reach Agreement with Mining Companies to clean up Berkeley Pit. US Department of Justice, March, 2002. (accessed: 2008-09-24)
  18. Hot Topic of the Day: Wednesday, March, 27, 2002. Missoulian.com, 2008-09-24.
  19. Official PitWatch website
  20. Official PitWatch website
  21. United States and Montana Reach Agreement with Mining Companies to clean up Berkeley Pit. US Department of Justice, March, 2002. (accessed: 2008-09-24)
  22. Official PitWatch website
  23. Hot Topic of the Day: Wednesday, March, 27, 2002. Missoulian.com, 2008-09-24.
  24. Hot Topic of the Day: Wednesday, March, 27, 2002. Missoulian.com, 2008-09-24.
  25. Hot Topic of the Day: Wednesday, March, 27, 2002. Missoulian.com, 2008-09-24.
  26. Hot Topic of the Day: Wednesday, March, 27, 2002. Missoulian.com, 2008-09-24.
  27. Berkeley Pit. Everything2.com, 2008-09-24.
  28. Berkeley Pit. Everything2.com, 2008-09-24.
  29. Matthews, Mark. Could a Toxic Lake Yield Life-Saving Microbes? Washington Post, March, 1999. (accessed: 2008-09-24)
  30. Maag, Christopher. In the Battle Against Cancer, Researchers Find Hope in a Toxic Wasteland. The New York Times, October, 2007. (accessed: 2008-09-24)
  31. Maag, Christopher. In the Battle Against Cancer, Researchers Find Hope in a Toxic Wasteland. The New York Times, October, 2007. (accessed: 2008-09-24)
  32. Maag, Christopher. In the Battle Against Cancer, Researchers Find Hope in a Toxic Wasteland. The New York Times, October, 2007. (accessed: 2008-09-24)
  33. Matthews, Mark. Could a Toxic Lake Yield Life-Saving Microbes? Washington Post, March, 1999. (accessed: 2008-09-24)