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Monitoring compliance points in the Berkeley Pit groundwater system

What is being done to manage the Berkeley Pit now?

The Horseshoe Bend Water Treatment Plant, completed in 2003, captures surface water to slow the rate of fill of the Berkeley Pit lake. In the future, the plant will capture and treat water to prevent Pit water from rising further. Photo by Justin Ringsak.
The Horseshoe Bend Water Treatment Plant, completed in 2003, captures surface water to slow the rate of fill of the Berkeley Pit lake. In the future, the plant will capture and treat water to prevent Pit water from rising further.

Water from the Horseshoe Bend drainage is diverted before reaching the Pit and treated in the Horseshoe Bend Water Treatment Plant for use in mining operations. In 2012, the plant treated about 5 million gallons of water per day. Sludge from the treatment process was returned to the Pit at a rate of 491,000 gallons per day. No water or waste leaves the Pit or mine site.

Water levels in the Pit, wells and mine shafts are monitored monthly. An evaluation of the rate of fill is performed each year to determine dates for future reviews and plant upgrades.

Berkeley Pit groundwater monitoring locations and water levels, including wells and abandoned mine shafts, June 2013. Graphic by Justin Ringsak.
Berkeley Pit groundwater monitoring locations and water levels, including wells and abandoned mine shafts, June 2013. Click on the image to view a larger version.
Monitoring compliance points in the Berkeley Pit groundwater system
Monitoring compliance points in the Berkeley Pit groundwater system. The water level a each point is monitored monthly by the Montana Bureau of Mines & Geology. When the water at any compliance point reaches the Critical Level (5,410 feet above sea level), pumping and treating of Berkeley Pit water will begin to prevent contaminated water in the Pit and groundwater system from spreading outward. Click on the image to view a larger version.

 

The Berkeley Pit looking west from Rampart Mountain near Butte, Montana. The Pit water and connected underground mines and wells are monitored monthly by the Montana Bureau of Mines & Geology. Photo by Matt Vincent.

How is the Pit monitored?

This image illustrates how the Berkeley Pit, with the lowest water levels in the area, acts as a sink that collects groundwater. Water levels indicated for each monitoring point are from June 2013.
This image illustrates how the Berkeley Pit, with the lowest water levels in the area, acts as a sink that collects groundwater. Water levels indicated for each monitoring point are from June 2013. Click on the image to view a larger version.

The Montana Bureau of Mines & Geology (MBMG) measures the water levels at the Pit and in connected mine shafts and wells each month. To monitor water quality, water samples are collected from the Pit semi-annually at multiple depths as safe access allows.

23 wells and 14 mine shafts supply information about the deep bedrock aquifer. 36 wells provide similar data about the alluvial aquifer, which is much closer to the surface. Each month, scientists manually check and record the water levels in these wells. Twice a year, they collect samples to analyze the water’s chemistry. All of this information helps scientists understand where the water is coming from and how it is moving underground.

Complete MBMG monitoring reports and data can be downloaded from our Monitoring Reports page.

The EPA also evaluates site progress and management through five year reviews. The third five year review for the Butte Mine Flooding Operable Unit (BMFOU), which includes the Berkeley Pit and underground mines, took place in 2011. For more information, or to download the 2011 report, click here.

Berkeley Pit groundwater monitoring locations and water levels, including wells and abandoned mine shafts, June 2013. Graphic by Justin Ringsak.
Berkeley Pit groundwater monitoring locations and water levels, including wells and abandoned mine shafts, June 2013.
The waterfall on the southeast rim of the Berkeley Pit, near the Horseshoe Bend Water Treatment Plant as it appeared in 2009. The waterfall has stopped flowing since a Feb. 2013 slough from the Pit wall knocked out a pump used for Montana Resources copper precipitation plant. Prior to Feb. 2013, the waterfall was created by Pit water returning after Montana Resources had removed most of the copper in the water in its precipitation plant. Photo by Justin Ringsak.

What was the waterfall on the northeast wall of the Pit?

The waterfall on the northeast rim of the Berkeley Pit, near the Horseshoe Bend Water Treatment Plant as it appeared in 2009. The waterfall has stopped flowing since a Feb. 2013 slough from the Pit wall knocked out a pump used for Montana Resources copper precipitation plant. Photo by Justin Ringsak.
The waterfall on the northeast rim of the Berkeley Pit, near the Horseshoe Bend Water Treatment Plant as it appeared in 2009. The waterfall has stopped flowing since a Feb. 2013 slough from the Pit wall knocked out a pump used for Montana Resources copper precipitation plant.

In past years, many visitors were curious about the waterfall visible from the Pit Viewing Stand. Montana Resources pumped water out of the Berkeley Pit, then removed the copper from that water before returning it to the Pit (click here for more information on mining copper from Pit water). The waterfall was created by this returning water. However, this activity stopped after the 2013 slough (click here for more information on the slough), so there is no longer a waterfall on the Pit rim.

The northeast rim of the Berkeley Pit in July 2013, after a Feb. 2013 slough from the Pit wall knocked out a pump used for Montana Resources copper precipitation plant. When the precipitation operation was ongoing, Berkeley Pit water was pumped to a precipitation plant where copper was removed from the water. The water was then returned to the Pit, creating the waterfall seen in past years. Photo by Fritz Daily.
The northeast rim of the Berkeley Pit in July 2013, after a Feb. 2013 slough from the Pit wall knocked out a pump used for Montana Resources copper precipitation plant. When the precipitation operation was ongoing, Berkeley Pit water was pumped to a precipitation plant where copper was removed from the water. The water was then returned to the Pit, creating the waterfall seen in past years.
The Horsheshoe Bend Water Treatment Plant at the Berkeley Pit

What is the Horseshoe Bend Water Treatment Plant?

The Horseshoe Bend Water Treatment Plant can be seen on the northeast edge of the Pit. The plant was constructed in 2002-2003 to fulfill the EPA Record of Decision, which requires that surface water flowing into the Berkeley Pit be captured and either used in the mining process or treated.

The Horseshoe Bend Water Treatment Plant, completed in 2003, captures surface water to slow the rate of fill of the Berkeley Pit lake. In the future, the plant will capture and treat water to prevent Pit water from rising further. Photo by Justin Ringsak.

The Horseshoe Bend Water Treatment Plant, completed in 2003, captures surface water to slow the rate of fill of the Berkeley Pit lake. In the future, the plant will capture and treat water to prevent Pit water from rising further.

The plant was designed to treat up to 7 million gallons of water per day using lime (calcium oxide) to raise the pH (reduce the acidity of the water) and remove metals. As pH rises, metals come out of the water and form sludge. The sludge is separated from the water and returned to the Pit at a current rate of about 491,000 gallons per day. Montana Resources incorporates the treated water into their mining process.download full movie The Discovery

In 2012 the plant treated about 5 million gallons of water per day. This water comes from the Horseshoe Bend drainage north of the Pit. The plant has been working continuously since it came online in November 2003. No water or waste leaves the Pit or mine site.

The Horeseshoe Bend Water Treatment Plant, seen here in 2009, was constructed in 2002-2003 to fulfill the EPA Record of Decision, which requires that surface water flowing into the Berkeley Pit be captured and either used in the mining process or treated. Currently the plant is used to capture and treat surface water that would otherwise flow into the Pit. Treated water is then used in Montana Resources mining operations. Photo by Justin Ringsak.

The Horeseshoe Bend Water Treatment Plant, seen here in 2009, was constructed in 2002-2003 to fulfill the EPA Record of Decision, which requires that surface water flowing into the Berkeley Pit be captured and either used in the mining process or treated. Currently the plant is used to capture and treat surface water that would otherwise flow into the Pit. Treated water is then used in Montana Resources mining operations.

A timeline projecting future Berkeley Pit management.

Will the Treatment Plant be able to meet the demand to pump-and-treat Pit water in the future?

A treatment pond at the Horseshoe Bend Water Treatment Plant (2009). Photo by Justin Ringsak.
A treatment pond at the Horseshoe Bend Water Treatment Plant (2009).

Yes, after a treatment technology review and upgrades to the plant are completed.

The 1994 EPA Record of Decision and 2002 Consent Decree require a review of treatment technologies when the Critical Water Level (5,410 feet) is about four years away. The review will consider the plant’s ability to treat both Pit water and water coming from the Horseshoe Bend drainage to the north. Based on the review, the Treatment Plant will then be upgraded to best treat the water.

Upgrades must be completed two years before the critical level is reached. Projections show water levels at one of the compliance points connected to the Pit will near the critical level around 2023, so a treatment review would take place in 2019, with any needed upgrades completed by 2021, as indicated by the timeline below.

This timeline reflects project changes agreed to in the Consent Decree that governs Berkeley Pit management. The timeline is reviewed and adjusted by the Montana Bureau of Mines & Geology each year. Any future timeline changes will be reported in PitWatch and on the PitWatch website at www.pitwatch.org. Graphic by Justin Ringsak.
This timeline reflects project changes agreed to in the Consent Decree that governs Berkeley Pit management. The timeline is reviewed and adjusted by the Montana Bureau of Mines & Geology each year. Any future timeline changes will be reported in PitWatch and on the PitWatch website at www.pitwatch.org. Click on the image to view a larger version.

 

Water in the Berkeley Pit rising over time, 1979-2013. Photos from the Montana Bureau of Mines & Geology, Justin Ringsak, and Fritz Daily.

1982-2013: 31 years since pumps stopped

Over 31 years ago economic factors led the Atlantic-Richfield Corporation, or ARCO, now a subsidiary of British Petroleum, to cease mining operations at the Berkeley Pit in Butte, Montana. Underground mining had come to an end seven years earlier, but the underground pumps had continued to operate, pumping groundwater out from the mines and the Berkeley Pit.

The 1982 suspension of mining coincided with the stoppage of pumping, allowing groundwater to begin rising in the underground mines and eventually into the Berkeley Pit.

Water in the Berkeley Pit rising, 1979-2013. Photos from the Montana Bureau of Mines & Geology, Justin Ringsak, and Fritz Daily.
Water in the Berkeley Pit rising, 1979-2013.

With ARCO’s suspension of mining in the neighboring East Berkeley Pit (now known as the Continental Pit) on July 1, 1983, the future of mining on the Butte Hill was uncertain at best.

EPA LogoSoon after, the Berkeley Pit was classified as a federal Superfund site by the United States Environmental Protection Agency (EPA). According to the EPA, a Superfund site is an uncontrolled or abandoned place where hazardous waste is located, possibly affecting local ecosystems or people.

The end of mining at the Berkeley also marked the beginning of the Berkeley Pit lake we see today. 3,900 feet deep underground in the Kelley Mine , the pumps used to dewater the underground mines and the Berkeley Pit ran until April 23, 1982. Without pumping, the Berkeley Pit began to fill with water flowing in from both surface runoff and groundwater. Due to the natural geochemistry of the area and mining activities, the water is highly acidic and contains high concentrations of dissolved heavy metals.

This image from the Montana Bureau of Mines & Geology illustrates the connections between historic underground mining tunnels and the Berkeley Pit. After groundwater pumping ceased in 1982, the tunnels, and eventually the Pit, began to fill with water.
This image from the Montana Bureau of Mines & Geology illustrates the connections between historic underground mining tunnels and the Berkeley Pit. After groundwater pumping ceased in 1982, the tunnels, and eventually the Pit, began to fill with water.

By 1985, ARCO had sold a portion of its holdings to Montana businessman Dennis Washington. Mining operations in the Continental Pit, as well as heap leaching of old Berkeley Pit leach pads, were resumed by his new company, Montana Resources.

The future site of the Berkeley Pit in Butte, Montana as it appeared in 1952.

1955-1982: Berkeley Pit history

The Berkeley Pit in 1963, shortly after the construction of the Weed Concentrator seen below the Pit, with the city of Butte, Montana to the bottom and right in the photo.
The Berkeley Pit in 1963, shortly after the construction of the Weed Concentrator seen below the Pit, with the city of Butte, Montana to the bottom and right in the photo.

Over the active lifespan of the Berkeley, approximately 320 million tons of ore and over 700 million tons of waste rock were mined from the Pit. Put another way, “The Richest Hill on Earth” produced enough copper to pave a four-lane highway four inches thick from Butte to Salt Lake City and 30 miles beyond.

The historic Berkeley mine in Butte, Montana, where the Berkeley Pit started in 1955. Photo from the Butte-Silver Bow Archives.
The historic Berkeley mine in Butte, Montana, where the Berkeley Pit started in 1955.

In 1955, mining in Butte saw the light, literally. Excavation on what would become the Berkeley Pit, named from one of several nearby historic underground mines that the Pit would later engulf, began that year in a transition from underground to open pit mining.

A street in Meaderville, one of the Butte neighborhoods destroyed to make way for Berkeley Pit expansion between 1955 and 1982. Photo from the Butte-Silver Bow Archives.
A street in Meaderville, one of the Butte neighborhoods destroyed to make way for Berkeley Pit expansion between 1955 and 1982.

The Pit would, in the next decade, swallow Butte neighborhoods like Meaderville, Dublin Gulch, and McQueen. The transition to open pit mining, a highly industrialized form of mining, also meant fewer jobs for the city’s miners. But mining had always been the lifeblood of Butte, and so the community embraced the new mine, and there was little objection to the sacrifice of some of the city’s neighborhoods.

The Anaconda Company’s decision to begin open pit mining in Butte was not without its reasons. In 1955, copper prices were the highest they had been since the end of World War I in 1918. And the following year, 1956, would mark the highest copper price seen until 2006 (with the exception of the lone year 1974, when copper briefly spiked due to an end to price controls and the ongoing demands of the Vietnam War).

The Holy Savior church, along with several historic neighborhoods in Butte, Montana, was buried to make way for Berkeley Pit expansion. Photo from the Butte-Silver Bow Archives.
The Holy Savior church, along with several historic neighborhoods in Butte, Montana, was buried to make way for Berkeley Pit expansion.

Those high prices gave the Company a big incentive to rethink its Butte operations. The most accessible parts of the Butte hill had already been mined out. Legend has it that Marcus Daly’s original ore vein was 30% copper. That is extraordinarily rich ore, and the veins of that quality could not last- as a point of comparison, when it opened, the ore mined at the Berkeley was about 0.75% copper, and the ore being mined at Montana Resources nearby Continental Pit operation today is approximately 0.25% copper. In order to economically extract copper from lower grade ore, the Pit was born.
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