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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 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.

Many students and teachers are learning about science by visiting the Berkeley Pit in Butte, Montana.

Many are learning from the Berkeley Pit

Many students and teachers are learning about science by visiting the Berkeley Pit in Butte, Montana.
Many students and teachers are learning about science by visiting the Berkeley Pit in Butte, Montana.

From grade school through college, many classes have visited the Pit in order to learn about science, mining, and the history of the region.

In the past year, students from not only the Butte area, but also from around Montana made the trip to the Pit. Middle school students from Bonner school  and college students from Montana State University-Billings and the University of Montana Environmental Studies programs have visited the Pit and the Butte area annually for the past few years.

Teachers as well as students are learning from the Pit and taking that knowledge back to their classrooms. For example, in 2007 Montana Resources provided a tour of the Pit and surrounding area for a group of 15 western Montana teachers. Seeing the Pit up-close and in-depth provides teachers with real-world examples of science concepts and issues that can then be used to engage students in the classroom.

These inquisitive spectators have learned about the details of the Pit from a variety of community volunteers and experts. Butte resident Joe Griffin, an environmental science specialist with the Department of Environmental Quality, offers students a comprehensive view of the science surrounding the Pit.

Tad Dale regularly takes time away from his busy schedule at Montana Resources to share his wealth of knowledge about the Pit and mining. Scientists from the Montana Tech faculty often come out to discuss the Pit in light of their specialties, whether it is Andrea and Don Stierle talking about biology and their research on the unusual microbes living in the Pit environment or Colleen Elliott presenting the geological context of the Pit.

And, of course, thousands of tourists learn about the Pit every year through the Butte trolley system, guided by knowledgeable locals like Butte High School history teacher Chris Fisk. Thanks to the contributions of knowledgeable Butte citizens like these, the Berkeley Pit viewing stand serves as an exciting classroom for exploring environmental sciences.

Controlled groundwater areas for Butte Superfund sites, including Superfund Operable Unit borders and monitoring points, from the 2011 EPA Five Year Review on Butte/Silver Bow Creek.

Priority Soils: The Other Superfund cleanup project in the Butte area

Controlled groundwater areas for Butte Superfund sites, including Superfund Operable Unit borders and monitoring points, from the 2011 EPA Five Year Review on Butte/Silver Bow Creek.
Controlled groundwater areas for Butte Superfund sites, including Superfund Operable Unit borders and monitoring points, from the 2011 EPA Five Year Review on Butte/Silver Bow Creek. Click on the image to view a larger version.

When the Horseshoe Bend Water Treatment Plant starts operating later this year, the contaminated waters from the Berkeley Pit and underground mines should be managed safely for years to come. In the meantime, another cleanup project – called the Butte Priority Soils Operable Unit – is just now reaching its critical decision point (i.e., the Record of Decision, scheduled by the end of 2003). Over the next several months, there will be a series of public meetings about this project, and the Committee would like to share information to help citizens understand the issues and encourage participation in the decision-making process.

Where is the Butte Priority Soils cleanup site?

Generally, the project includes the residential yards and mine dumps on the Butte Hill and in Walkerville, and the water drainages weaving down the Hill to Silver Bow Creek. The site is about five square miles and includes most of the urban area from Walkerville on the north to Silver Bow Creek on the south, along with the Clark Tailings below Timber Butte.
It’s also important to understand what the Priority Soils does NOT include. It’s separate from the Berkeley Pit and underground mine flooding project, which, as we’ve reported in PITWATCH for several years, is the responsibility of Arco and Montana Resources. The Priority Soils is also separate from the Montana Pole cleanup and the Streamside Tailings project along Silver Bow Creek, both of which are ongoing and the responsibility of Montana Department of Environmental Quality. In the big picture, all these cleanup activities will have to fit together, but for now, Priority Soils stands alone.

What is the cleanup task?

The job is two-fold:

  1. to eliminate direct contact with mine waste on the Hill, thus protecting human health; and
  2. to prevent the heavy metals in those mine waste materials from getting into storm water and groundwater and finding their way to Silver Bow Creek, thereby protecting life in the stream and the DEQ’s $85 million creek cleanup project.

Is some work already complete?

Yes. In fact, a substantial amount of the cleanup of Priority Soils has occurred – about $50 million of work by current estimates. Over the past 15 years, several projects have been completed, with the understanding that all this work will be reviewed as part of the final decision. Major projects include: the Alice Pit/Dump (1998); several areas in Walkerville (1988, 1994, 2002); the Missoula Gulch, Buffalo Gulch and Kelley ditches and retention ponds (1997-99); railroad corridors (2001-03); and Lower Area One, including the reconstructed Silver Bow Creek, the Colorado Tailings removal, and the Clark Tailings project (1993-2000).

In all, more than 175 mine dumps covering more than 400 acres have been partially removed and capped, and more than 180 residential yards have been cleaned up (lead soil removals). The caps generally consist of placing 18″ of clean soil materials with organic amendments over the wastes and planting native vegetation to hold the soil in place and minimize erosion. To complement the caps, a system of storm water collection facilities – the new drainage ditches and retention ponds – has been installed to collect water that may still contain heavy metals and prevent those contaminants from reaching Silver Bow Creek.

What Other Areas and Issues Must Be Addressed?

The major cleanups still ahead include the Parrot Tailings near the Civic Center and the Metro Storm Drain corridor, which once was the historic Silver Bow Creek channel that flowed through town, and a large area north of the Kelley Mine, surrounding the Mountain Con Mineyard and the Granite Mountain Memorial.

In addition to cleanups, other issues include deciding what type of water treatment system should be used to ensure groundwater, surface water or storm water leaving the area will not pollute Silver Bow Creek heading west of town. Another big decision will be to determine whether the projects already completed were done satisfactorily and will be permanent, or whether additional work is needed.

Perhaps the most important issue is to determine how the reclaimed areas and water management facilities will perform in the long term and be effectively maintained. As part of the Record of Decision, it will be critical to set the right performance standards for treatment and long-term care, and then determine how much money it will take to get the job done properly.

Is Butte on the hook for the Priority Soils cleanup?

Unlike every other cleanup around Butte, where the citizens have been protected from any Superfund liability, Butte-Silver Bow was named as a Potentially Responsible Party or PRP to conduct the Priority Soils cleanup. In 1990, EPA decided that since the publicly owned storm water system carried wastes off the Hill to the creek, the community was partly liable for the problem.
However, Arco is also a PRP for Priority Soils, and for the most part over the past 15 years, Arco has paid all costs for cleanup work. As part of the upcoming Record of Decision and then a Consent Decree for the Priority Soils project, Butte’s “share” will be determined.

For much more on Butte Priority Soils and other area Superfund projects, visit the Citizens Technical Environmental Committee (Butte CTEC) website.

Consent Decree Announced


Berkeley Pit, 2006.
Berkeley Pit, 2006. Click on the image to view a larger version.

Pitwatch Issue Volume 7, Number 1

In March 2002, the Atlantic Richfield Company (ARCO) and Montana Resources (MR) agreed to sign a Consent Decree, a legally binding document that will be entered in federal court. The Consent Decree requires these companies to reimburse EPA and DEQ for past costs, and pay now for future oversight costs. It also guarantees that these companies will perform a number of tasks and provide financial assurances to pay all costs to complete the required work.

Most importantly, the Consent Decree sets a firm schedule for Arco and MR to build a water treatment facility, and confirms their obligations to operate and maintain the facility – including sludge disposal – in perpetuity. Also included in the Consent Decree are commitments to enhance the waterfowl protection program at the Berkeley Pit, to establish a groundwater control area surrounding the Berkeley, to fund the Montana Bureau of Mines and Geology (through the EPA and DEQ) to continue the mine flooding monitoring program, and to fund public education activities (e.g., PITWATCH).

As part of the process, ten changes were made to the Record of Decision (1994). For example, changes were made to recognize new stream and discharge standards for the treated water, to allow Continental Pit water treatment in the Horseshoe Bend plant, and to allow sludge disposal in the Berkeley Pit. Another change eliminates the requirement to reevaluate treatment technologies when the water level in the Pit reaches the 5,260′ level, since the treatment plant will already be built. The Consent Decree also clarifies which cleanup tasks will be done under the Superfund program and which will be done under the State’s active mine permit reclamation program.

The Consent Decree was released on March 26, 2002 for public comment until May 4, and is expected to be finalized thereafter. Contact the Committee with any questions.