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The water level in the Berkeley Pit in 2013, compared to the Critical Water Level. Current projections show that the water level in one of the monitoring compliance points around the Pit, such as the Pilot Butte or Anselmo mine shafts, will reach the critical level around 2023, triggering pumping-and-treating of Pit water to maintain its level below the critical point. Photo by Ted Duaime of the Montana Department of Mines & Geology.

Current and Critical Water Level Comparison

The 2013 print edition of PitWatch included the following photo from the Montana Bureau of Mines & Geology (MBMG), intended to show the current water level relative to the Critical Water Level.

The water level of the Berkeley Pit in 2012, compared to the Critical Water Level for the Berkeley Pit system. Image from the Montana Bureau of Mines and Geology.
The water level of the Berkeley Pit in 2012, compared to the Critical Water Level for the Berkeley Pit system.

Some PitWatch readers asked for a version of this image that used a current photo of the Berkeley water level, and MBMG created this new image to better illustrate the current and critical levels.

The water level in the Berkeley Pit in 2013, compared to the Critical Water Level. Current projections show that the water level in one of the monitoring compliance points around the Pit, such as the Pilot Butte or Anselmo mine shafts, will reach the critical level around 2023, triggering pumping-and-treating of Pit water to maintain its level below the critical point. Photo by Ted Duaime of the Montana Department of Mines & Geology.
The water level in the Berkeley Pit in 2013, compared to the Critical Water Level. Current projections show that the water level in one of the monitoring compliance points around the Pit, such as the Pilot Butte or Anselmo mine shafts, will reach the critical level around 2023, triggering pumping-and-treating of Pit water to maintain its level below the critical point. Photo by Ted Duaime of the Montana Department of Mines & Geology.

Under the management plan for the Berkeley Pit, the water level in the Pit itself will never reach that critical level. Because water levels in some of the compliance monitoring points around the Pit are consistently higher than the level in the Pit itself, it is extremely likely that water at one of those monitoring points (such as the Pilot Butte or Anselmo mine shafts) will reach the critical level while the Berkeley Pit water level is still several feet below it. When the water level at any compliance point reaches the critical level (current projections put this time at 2023), pumping-and-treating of Berkeley Pit water will begin, maintaining the level in the Pit below the critical level.

Berkeley Pit water quality has shown changes over time. It is regularly monitored by the Montana Bureau of Mines & Geology. The reddish color typically observed is due to high concentrations of iron solids. Photo by Justin Ringsak, 2009.

What’s in the Berkeley Pit water?

The water level at the Berkeley Pit has been recorded every month for more than 23 years. In addition to that monitoring, scientists at the Montana Bureau of Mines and Geology have been sampling and analyzing water from the Berkeley Pit twice a year for its chemical composition and physical properties.

Berkeley Pit Facts 2013. Graphic by Justin Ringsak.

In the Berkeley Pit, samples are taken from anywhere between three to nine different depths and analyzed for various dissolved chemicals.

Berkeley Pit water quality has shown changes over time. It is regularly monitored by the Montana Bureau of Mines & Geology. The reddish color typically observed is due to high concentrations of iron solids. Photo by Justin Ringsak, 2009.
Berkeley Pit water quality has shown changes over time. It is regularly monitored by the Montana Bureau of Mines & Geology. The reddish color typically observed is due to high concentrations of iron solids.

Water quality conditions, such as temperature, pH, specific conductance, and dissolved oxygen, are also measured at five- to ten-foot intervals from the surface to a depth of 600 feet. These same conditions are also measured at a depth near the Pit bottom.

In past years, the Berkeley Pit was a chemically layered system, which means that the chemistry of the water changed with depth. The brownish-red water at the surface was actually the least contaminated water in the pit, and the lower layer the worst water quality. The color changed as well, going from brownish-red on top to bluish-green at the bottom.

At a certain depth, the chemistry of the water changed so rapidly that it formed a chemical boundary scientists refer to as a chemocline. Water above the chemocline was chemically lighter, in other words, less dense, than the water below. The layering of the two waters is similar to oil floating on water. The water above the line was also less acidic (higher pH), with lower concentrations of metals.

A chemocline, or a difference in water chemistry depending on water depth, was seen in the Berkeley Pit prior to about 2011. Since that time, mixing of the water in the Pit lake has  caused the water chemistry to become more uniform. Graphic by Justin Ringsak.
A chemocline, or a difference in water chemistry depending on water depth, was seen in the Berkeley Pit prior to about 2012. Mixing of the water in the Pit lake over time has caused the water chemistry to become more uniform. Click on the image to view a larger version.

Due to mixing in the Berkeley Pit lake over time, this previously layered system disappeared around 2012, and the Pit water has since become more uniform.

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.

Water treatment plant working as expected

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.

Looking northeast from the Berkeley Pit viewing stand, visitors can see one of the most important components in the future management of the Pit: the Horseshoe Bend Water Treatment Plant. Sitting on four acres near the former McQueen neighborhood, about 600 feet east of the Berkeley Pit, the treatment plant was constructed in 2002-2003. It sits on native land that is very stable, and the plant was built to withstand the maximum probable earthquake.

The facility was designed to treat up to seven million gallons per day, or about 5,000 gallons of water per minute. The facility cost approximately $18 million to build, and, depending on how much water is treated, operating expenses run about $2 million per year.

Once the Berkeley Pit water comes online, which is projected to happen in 2023, annual operation and maintenance costs could be as high as $4.5 million. Under the terms of the 2002 Consent Decree negotiated with the government, BP-ARCO and Montana Resources have agreed to provide financial assurances to pay operation and maintenance expenses in perpetuity. The two companies also paid all construction costs for the facility.

The actual construction of the treatment plant was a massive undertaking. It is estimated that workers put in 125,000 hours of total labor, and the facility also required more than 4,500 cubic yards of concrete.

The general construction contractor and subcontractors were all from Montana, with several from Butte, and, during the course of construction, they reported no safety incidents of any kind.

As per the schedule listed in the 1994 EPA Record of Decision and included in the 2002 Consent Decree, based upon current water level projections, a review of the Horseshoe Bend Water Treatment Plant design and operation would begin in 2019. Any necessary upgrades would have to be completed by 2021, two years before Pit water itself is currently projected to be pumped and treated in 2023.

In November, 2007, a performance review of the Horseshoe Bend plant was completed by Montana Resources, ARCO, and North American Water Systems, with cooperation from the Montana Bureau of Mines & Geology, the Department of Environmental Quality, and the EPA.

The performance test was undertaken to ensure that the treatment system is capable of meeting the water quality standards set in the Consent Decree for the site. For this test, only water from the Horseshoe Bend drainage was treated, as water from the Pit is not yet required to be pumped and treated at the plant.

The test began on November 18, 2007, and continued for 72 hours. All of the water quality standards for contaminants of concern were met. Additional adjustments still need to be made to address pH. For this test, the pH was kept at a high (basic or alkaline) level in order to effectively remove contaminants of concern and meet water quality standards.

The optimization of the plant in the future may result in a lower pH. Additionally, methods of adjusting the pH prior to discharge to Silver Bow Creek have been evaluated conceptually. Any method of adjusting the pH will be formally evaluated, if necessary, before any water from the plant is discharged to Silver Bow Creek.

Limnocorrals, experimental enclosures which physically isolate a known volume of water and allow for the testing of various experimental manipulations at a relatively low cost, deployed in the Berkeley Pit. Photo by Nicholas Tucci.

Research continues on Pit Water

The unique environment of the Berkeley Pit and the surrounding Butte area has created numerous avenues for scientific exploration, both by local scientists and by researchers around the globe.

The research potential of the site is tremendous, and may represent a real renaissance for a geographic area characterized by years of mining, milling, and smelting waste. Research efforts have been undertaken locally at Montana Tech, the Montana Bureau of Mines and Geology, and MSE, and research groups from around the world have studied Pit water.

On a more local level, a cursory scan of Montana Tech Library resources turns up 23 thesis publications devoted specifically to researching aspects of the Berkeley Pit, as well as many more Pit-related research publications. And the research covers a diverse array of topics, including environmental engineering, geology, communications, metallurgy, chemistry, and physics.

A 1994 thesis by David Klemp, a graduate student in the Montana Tech Environmental Engineering program, investigated fog from Berkeley Pit water, a site familiar to most Butte residents. A 1996 thesis by Neil Massart, also from the Environmental Engineering program, offered an economic analysis of a crystallization process that was part of a broader evaluation of the potential for innovative technologies to remediate the Pit.

A large volume of additional research has focused on the study of various methods for bioremediating Pit water or the use of different technologies to treat Pit water. Other studies, like that carried out by Montana Tech Chemistry and Geochemistry graduate student Licette Hammer in 1999 and a similar study done by graduate student Margery Willett in 2001, focus on the amount and types of organic carbon present in the Pit, and the relationship between organic carbon and the larger Pit ecosystem.

In addition to the regular staff of scientists and undergraduate assistants at Montana Tech, the Stierles, at center, have also worked with local high school and middle school students over the years on science fair projects focused on Berkeley Pit microbes. The realization that a compound that could help cure cancer could be lurking in the Berkeley Pit is thrilling. They like to think that their microbes could be some of the richest "ore" ever mined from the Richest hill on Earth. Photo courtesy of Lisa Kunkel, The Montana Standard.
In addition to the regular staff of scientists and undergraduate assistants at Montana Tech, the Stierles, at center, have also worked with local high school and middle school students over the years on science fair projects focused on Berkeley Pit microbes. The realization that a compound that could help cure cancer could be lurking in the Berkeley Pit is thrilling. They like to think that their microbes could be some of the richest “ore” ever mined from the Richest hill on Earth. Photo courtesy of Lisa Kunkel, The Montana Standard.

Local scientists Drs Andrea and Don Stierle, both faculty members in the Department of Chemistry and Geochemistry at Montana Tech, recently garnered national publicity for their research, ongoing since 1996, on microbes living in the Berkeley Pit Lake. The unique nature of the Pit environment creates habitat for unusual microbes, sometimes called “extremophiles”, which could in turn produce novel chemistry with potential medical uses. The organisms themselves may also be effective bioremediators of the wastewater in which they grow.

The Stierles, aided by undergraduate research assistants at Montana Tech and local high school students and collaborating with scientists at Montana State University and the University of Montana, are “mining” these Pit microbes. They have already isolated several exciting new compounds, including a migraine preventative and several compounds with promising anticancer potential. They have also found an intriguing fungus that appears to pull metals from the Pit water itself.

The research process is complex. Microbes must first be isolated from water and sediment samples and established in pure cultures. A variety of carbon and nitrogen sources are used to determine which growth conditions yield the most active natural products. Extracted microbial cultures are tested to determine if they have potential as antibacterial, antifungal, anticancer, or immune system modulating agents.

The Stierles have been awarded almost $3 million in federal funding from the National Institutes of Health and the US Geological Survey to support their ongoing efforts at drug discovery from an acid mine waste lake.

Other scientists have experimented with the potential of algae to clean or bioremediate the Berkeley Pit. For most of the past decade, Dr. Grant Mitman, a Montana Tech biology professor, has been studying the ability of algae to remove heavy metal contaminants from Pit water. Through various metabolic, physiological, and biochemical processes, algae have the potential to reduce soluble metal ions in acid mine waters.

Limnocorrals, experimental enclosures which physically isolate a known volume of water and allow for the testing of various experimental manipulations at a relatively low cost, deployed in the Berkeley Pit. Photo by Nicholas Tucci.
Limnocorrals, experimental enclosures which physically isolate a known volume of water and allow for the testing of various experimental manipulations at a relatively low cost, deployed in the Berkeley Pit.

Dr. Mitman, along with graduate student Nicholas Tucci, applied this potential bioremediation solution in the Berkeley Pit in 2006. Algae occur naturally in the Pit, but lack nitrate, a common nutrient found in most fertilizers that is essential for algal growth. If nitrate is added to Pit water, the naturally occurring algae can potentially reach a concentration of millions of cells per milliliter, a virtual green soup of suspended organisms that have an ability to permanently remove dissolved metals from the pit. These organisms have been used to remediate other pit lakes around the world, and may one day lead to the natural restoration of the Berkeley Pit.

In the spring of 2004, Mitman and Tucci deployed nine acid- and metal-resistant cylindrical limnocorrals along the eastern edge of the Berkley Pit Lake. Limnocorrals are experimental enclosures which physically isolate a known volume of water, and allow for the testing of various experimental manipulations at a relatively low cost.

In this case, 500 gallons of pit water were used to fill the limnocorrals, and varying concentrations of nitrate were added as the experimental variable.

To determine if algal growth had an effect on Berkeley Pit water, water quality and algal populations in nutrified limnocorrals were continually monitored and compared with those in non-nutrified limnocorrals.

After the first year of data collection, concentrations of algae in the nutrified limnocorrals had increased from undetectable levels to two million cells per milliliter, and, as a result of this algal growth, both iron and arsenic concentrations in Pit water were significantly reduced. No significant changes in water quality or algal growth were detected in the non-nutrified limnocorrals.
Researchers are planning longer-term experiments testing the ability of algae to clean Berkeley Pit water. Algae, like other biological organisms, need time to achieve a substantial and healthy population. Long term experiments will be necessary to fully determine the potential for bioremediation in the Berkeley Pit.

While substantial research has been done on the Pit, there is clearly still a lot to learn. That is an exciting prospect for the Butte community, and in the future what we can learn from the Pit could represent the greatest treasure of the Richest Hill on Earth.