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Current Water Level: 5,290.90 ft Updated: 10.27.10 |
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Summer 2009
Comprehensive Berkeley Pit Information
1955: The year it all began
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.
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 swallow, began that year in a transition from underground to open pit mining.
The Pit would, in the next decade, swallow Butte neighborhoods like Meaderville, Dublin Gulch, and McQueen. The transition to open pit mining, a highly mechanized 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).
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 Continental Pit operation today is approximately 0.35% copper.
In order to economically extract copper from lower grade ore, the Pit was born.
Aside from, and more important, than economic motives, the Pit was also opened because of the simple fact that open pit mining is much less hazardous for the miners themselves. Best guesses put the number of deaths in Butte’s underground mines, which operated for about a century, from the 1860’s through 1976, at around 2,500, an average of about 25 deaths per year. Only six fatalities occurred over the life of the Berkeley, which was operated for 27 years from 1955 through 1982. The Continental Pit, which has been mined intermittently since 1980, has seen only one death.
But steep, continuous declines in copper prices following the 1974 spike led to the eventual shut down of Berkeley operations in 1982.
Throughout the history of mining in Butte, pumps were used to dewater the underground mines and, later, the Berkeley Pit. On April 23, 1982, ARCO, the owners of the former Anaconda Company holdings, announced that they were suspending their Butte operations. Along with the announcement, the underground pumps in the Kelley Mine were shut down. The result: the underground mines and the Berkeley Pit began to fill with acidic water.
The great advantage of the Berkeley is that it acts as a terminal sink: all contaminated ground and surface waters from Butte’s East Camp flow to it and are captured in it. Since 1982, ARCO, Montana Resources, the EPA, the DEQ and the local community have risen to the unique challenges of managing the Pit.
Historically, Butte’s resourcefulness made it a successful mining town that has far outlived the boom-and-bust cycle of many similar communities. That resourcefulness is today being applied in new ways in the many environmental restoration projects underway in the area, and in the management of the Berkeley Pit, all while mining continues successfully, and in ways that alleviate the impacts on the environment, just next door to the Berkeley at the Continental Pit.
In fact it can be said that mining continues today in the Berkeley Pit as Montana Resources copper recovery project is recovering the dissolved copper that exists in the water contained within the walls of the Pit (see "Montana Resources mines the water" for details).
Just as Butte transitioned from underground to open pit mining in 1955, in 2009 we are in the midst of an exciting transition from a landscape scarred by mining to a landscape that is restored where possible and managed responsibly.
Butte has the dubious distinction of being at the upper end of the largest complex of federal Superfund sites in the U.S. This Superfund complex extends from Butte and Anaconda 120 miles down the Clark Fork River to Missoula.
The word “Superfund” is tossed around a lot by local and state officials working in the Clark Fork Basin, but, to the average citizen of western Montana, the term might not mean very much. Nevertheless, Superfund is changing the landscape of western Montana, from the Berkeley Pit to the Anaconda Smelter all the way downstream to the former Milltown Dam.
In simple terms, Superfund refers to the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of 1980. This federal law, passed in the wake of environmental disasters like Love Canal, was designed to clean up abandoned hazardous waste sites that may endanger public health or the environment.
The law authorizes the Environmental Protection Agency (EPA) to identify parties responsible for contamination of sites and compel the parties to clean up the sites. Where responsible parties cannot be found, EPA is authorized to clean up sites itself using federal funding.
The Superfund cleanup process is very complex. It involves the steps taken to assess sites, place them on the National Priorities List, and establish and implement appropriate cleanup plans. This is the long-term cleanup process. EPA also has the authority to remove hazardous wastes where immediate action needs to be taken; to enforce against potentially responsible parties; to ensure community involvement; to involve states; and ensure long-term protection.
According to the EPA, as of May 26, 2009, there are 1,264 sites listed on the National Priority List, an additional 332 have been delisted, and 67 new sites have been proposed. There are currently 14 National Priority List sites in Montana, and two proposed sites.
Over 27 years ago, back in 1982, economic factors led the Atlantic-Richfield Corporation, or ARCO, now a subsidiary of British Petroleum, to cease mining operations at the Berkeley Pit. While underground mining had come to an end seven years earlier, the underground pumps continued to operate, pumping groundwater 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. 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. Soon 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 (see page 2).
The end of mining at the Berkeley also marked the beginning of the Berkeley Pit lake we see today. Deep in the Kelley Mine at the 3,900-foot level, the pumps used to dewater the underground mines and the Berkeley Pit ran until April 23, 1982. Without pumping, the Berkeley began to fill with water flowing into the Pit from both surface runoff and groundwater. Due to both the natural geochemistry of the area and mining activities, the water is highly acidic and contains high concentrations of dissolved heavy metals.
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.
In 1994, EPA and the Montana Department of Environmental Quality (DEQ) issued the Record of Decision (ROD) for the Butte Mine Flooding Operable Unit, which includes the Berkeley Pit. The ROD, according to the EPA, is a technical and legal document that: 1) summarizes the science behind the cleanup decision; 2) demonstrates how the remedy selection process was carried out; and 3) provides a thorough site history and includes public concerns, comments, and EPA responses.
In 1996, as directed in the ROD, water flows from Horseshoe Bend, a drainage to the north of the Berkeley Pit, were diverted away from the Berkeley and instead pumped up to the Yankee Doodle Tailings Pond that sits along the west slope of Rampart Mountain. At this facility, the ground-up rock (also known as tailings) that is generated as a byproduct of the milling process is deposited in order to settle out the solids and recycle decanted water back into the mill system. The Horseshoe Bend diversion reduced the rate at which the Berkeley was filling with water, keeping up to 3,000 gallons per minute of surface water from flowing into the Berkeley.
In 1998, Montana Resources began pumping water out of the Berkeley Pit for copper recovery, a technique still used at the mine today. The copper-rich water is pumped over scrap iron, and, in a replacement reaction, the copper solidifies as sludge, while iron takes its place in the water, which returns to the Pit by gravity flow, thus not increasing or decreasing the total volume of Pit water.
The diversion of water from Horseshoe Bend was discontinued on June 30, 2000, when increased costs led Montana Resources’ Continental Pit mine to shut down. As a result of this shutdown, conditions contained in the 1994 ROD required Montana Resources and ARCO to begin design and construction of a water treatment plant. But, with copper prices rising, the mine again reopened in 2003, since which time it has continued to operate. Shortly after the Continental Pit reopened, the Horseshoe Bend Water Treatment Plant went online ahead of schedule on November 17, 2003, again diverting Horseshoe Bend flows and preventing this water from entering the Pit. The Horseshoe Bend plant, which will eventually be used to pump and treat Pit water in order to keep it below the critical level, uses lime (calcium hydroxide) addition to reduce the acidity of the water and cause metals to precipitate out. In the long term, treated Horseshoe Bend water and, eventually, Berkeley Pit water will be used by the active mine as long as it is operating. Montana Street, the official beginning of Silver Bow Creek.
Since the day the pumps in the Kelley turned off in 1982, water levels have risen over 3,100
feet in the East Camp bedrock system (which includes the Berkeley Pit, as well as the surrounding underground mine workings and bedrock aquifer), and over 230 feet in the separate West Camp system. Water-levels have changed very little in the shallow alluvial system adjacent to historic mining operations (see page 6 for details on the bedrock and alluvial aquifers). Current projections anticipate that pumping and treating of Berkeley Pit water will need to commence in 2023, although that date is dependent upon many factors: a reduction in waters flowing into the Berkeley would push the date further into the future, whereas an increase in water flows would necessitate an earlier date. The results from a performance test conducted in November 2007 indicate that the Horseshoe Bend Water Treatment Plant meets all discharge standards for contaminants of concern set by the EPA. Additional adjustments still need to be made to address pH issues (see page 10 for details).
Photos: 1) Holy Savior church in McQueen was buried to make way for Pit expansion; 2) The Berkeley Mine in the background was the starting point for digging the Berkeley Pit. Rich ore veins below the surface made it the logical place to begin open-pit mining.
What's in the Berkeley Pit water?
The water level at the Berkeley Pit has been recorded every month for more than 18 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. Here's an update on some of the results:
In the Berkeley Pit, samples are taken from anywhere between three and nine different depths and analyzed for various dissolved chemicals. Water quality conditions, such as temperature, pH, specific conductance, and dissolved oxygen are also measured at five to 10-foot intervals from the surface to a depth of 600 feet. These same conditions are also measured at a depth near the Pit bottom.
The Berkeley Pit is a chemically layered system, which means that the chemistry of the water changes with depth. The brownish-red water at the surface is actually the least contaminated water in the pit, and the lower layer the worst water quality. The color changes as well, going from brownish-red on top to bluish-green at the bottom.
At a certain depth, the chemistry of the water changes so rapidly that it forms a chemical boundary scientists refer to as the chemocline. Water above the chemocline is 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 is also less acidic (higher pH), with lower concentrations of metals. The two layers of water never mix unless stirred. The last time the two mixed was believed to be after a 1998 landslide that resulted in 1.3 to 1.5 million cubic yards of materials sloughing from the southeast wall of the Pit into the water.
Scientists believe this chemical stratification was caused by the many years that water from the Horseshoe Bend drainage was diverted into the Berkeley Pit. The water chemistry of the Horseshoe Bend drainage is less contaminated and less dense, so it simply remained on top of existing Pit water, creating the sharp division.
Tracking the chemocline is important to mine operators. For several years, Montana Resources has operated a process to recover copper from Berkeley Pit waters. In order to reap the most benefit, the mine needs to extract metals-rich water from below the chemocline, where there is more dissolved copper. The cementation process used in the “precip plant” results in water that has much less copper and much more iron. This water is then returned to the Pit, which increases the iron content of the water in the upper layer. This has caused the dividing line to drift downward in recent years, and as a result, Montana Resources has had to lower the pump intake.
In the future, the water chemistry in the Berkeley Pit is expected to continue to change. As described above, water recycling for copper recovery is changing the chemistry. Couple that with the fact that the lighter Horseshoe Bend water is no longer entering the Pit, and there will likely be a scientific debate over whether Berkeley will remain a chemically stratified system.
This question and others will only be answered through periodic sampling and continuous monitoring. The chemical changes of the Berkeley Pit will continue to be recorded year after year by the Montana Bureau of Mines and Geology as part of their responsibilities under the 2002 consent decree for this Superfund site.
As illustrated above, the quantity of metals dissolved in the Berkeley Pit water is much greater below the chemocline than above it. The deeper water is also more acidic (lower pH).
40 billion gallons: where does it come from?
When ARCO suspended underground pumping operations in 1982, groundwater levels on the Butte Hill began to rise. Nineteen months later the water level in the underground workings and surrounding bedrock reached the bottom of the Pit, allowing bedrock groundwater to start filling the Pit void.
Prior to that time alluvial groundwater seeped into the Pit from the east and south walls, beginning to fill the pit sump. ARCO also diverted water from its mining operations (leach pad water, Continental Pit, Horseshoe Bend, etc.) into the Pit following the 1983 shutdown of their entire Butte operations.
When Montana Resources began operations in 1986 a number of these surface water sources were diverted away from the Pit, however, the Horseshoe Bend water continued to flow into the Pit until April 1996 when it was incorporated in Montana Resource’s mining operations for treatment and disposal in the Yankee Doodle Tailings Dam.
When Montana Resources suspended mining operations from 2000 through 2003, about 7.5 billion gallons of water, or an average of 6 million gallons per day, went into the Pit. Of this total, an average of 3.4 million gallons per day came from rising groundwater flows in the underground mine workings and surface stormwater flow. An average of 2.6 million gallons per day came from the Horseshoe Bend drainage.
Montana Resources also diverted water from the Continental Pit into the Berkeley Pit for containment during their suspension.
Since the Horseshoe Bend Water Treatment Plant began operating in 2003, water flows from the Horseshoe Bend drainage have been diverted to the treatment plant. After treatment, this Horseshoe Bend water is entirely recycled or consumed in mining operations, or, in other words, no water is discharged off of the site.
About 2.6 million gallons per day from groundwater and stormwater still flow into the Pit, contributing to the rising level there. Eventually, when the water level approaches the critical level of 5,410 feet above sea level, water will be pumped from the Berkeley Pit and treated at the Horseshoe Bend facility. Present projections put this date around 2023. Having the plant in place provides assurance that the capability to manage Berkeley Pit water levels is there when it becomes necessary to treat Pit water.
If the mine was to suspend operations again, Horseshoe Bend drainage water would be treated to discharge standards at the plant, then transported by a pipeline constructed along the reconstructed Silver Bow Creek channel, also known as the Metro Storm Drain, to a point upstream from its confluence with Blacktail Creek near Montana Street. The flow from Blacktail Creek would further dilute the treated water, resulting in even lower concentrations of metals or other minerals.
Two aquifers feed into the Pit
Aquifers are places where water is found in permeable rocks and soils underground. The area around the Berkeley Pit contains two main underground aquifers - the alluvial aquifer and the bedrock aquifer. The alluvial aquifer is closer to the surface. Water flows freely through the layer of ground called the alluvium, a porous mixture of sands, gravels, and clays. Near the east wall of the Pit, the alluvium is saturated with water from this aquifer.
The bedrock aquifer runs deep below the ground. It is a "confined aquifer" trapped within fractured bedrock which water cannot easily pass through. In areas adjacent to historic mining activities, this aquifer was dewatered by large pumps located underground to allow for underground mining. Up to 5,000 gallons of water per minute were pumped from the underground mines to allow for mining, including the Berkeley Pit.
The large stainless steel pumps located in the Kelley Mine were turned off in 1982, and since that time the dewatered area has been filling back up.
These two aquifers are independent systems, separated by a thick layer of clay-rich weathered bedrock that hinders water from the alluvial aquifer from seeping down into the bedrock aquifer. Instead, water from both aquifers is flowing toward the Pit because it is the lowest spot in the area.
Monitoring wells installed throughout the area are used to closely track the water levels and the water quality of both aquifers. Since monitoring began, the alluvial aquifer has remained fairly constant, fluctuating only a few feet here and there depending on seasonal precipitation.
In contrast, the water levels of the bedrock aquifer in areas of historic dewatering have been steadily rising to pre-mining levels. Water levels in the bedrock system have risen hundreds of feet and show minimal seasonal trends.
The monitoring wells also allow scientists to measure the pressure differential between the two aquifers, expressed in pounds per square inch, or psi.
The downward pressure of the alluvial aquifer is much greater than the upward pressure of the bedrock aquifer. Even if the bedrock barrier separating the two aquifers was not there, water migration would still be downward, from the alluvium into the bedrock, because of this stronger downward pressure, technically referred to as the downward gradient.
The downward gradient will keep water confined within the Berkeley Pit even though the water level has reached the bedrock-alluvial interface at about the 5,260-foot level. At that level, the water in the Pit has come in contact with both aquifers, but pressure has continued to move water downward and toward the Pit, thus preventing contaminated water from entering the alluvial system.
The gradient would eventually reverse if the Pit water were to rise unchecked; however, the establishment of a maximum elevation (5,410 feet) for bedrock groundwater in the East Camp system will prevent water levels from reaching this critical point.
Pumping and treatment of Pit water will be well underway when the water in the Pit—or in any of the numerous monitoring wells—approaches the critical level. The Horseshoe Bend Water Treatment Plant, which went online in 2003 and is already operational, is equipped to treat the water that will eventually be pumped from the Berkeley Pit.
The 2002 Consent Decree established eight compliance points throughout the East Camp system and stated that the bedrock water level could not exceed the 5,410-foot critical water level at any of these sites.
If present trends continue, the monitoring and compliance point at the Anselmo shaft, which regularly marks the highest current water level on the Butte Hill, will be the first point to approach 5,410 feet. When that occurs, pumping and treatment of Pit water will commence.
The amount of water in the alluvial aquifer, close to the surface, fluctuates with the seasons. The bedrock aquifer is filling back up to pre-mining levels. Pressure moves the water downward toward the Pit.
West Camp also part of mine flooding site
The anatomy of the thousands of miles of tunnels beneath the Butte Hill is daunting to consider and little understood by many. Important details, such as the distinction between the “West Camp” and “East Camp”, can cause consternation for many a curious observer.
The Berkeley Pit and surrounding underground mine workings and bedrock wells are referred to as the “East Camp”, and are separate from the “West Camp”, which is located more to the south and west. The Camps essentially refer to two water systems. In the East Camp, surface and underground water flows to the lowest point in the system, namely, the Berkeley Pit. The West Camp, whose waters never reach the Berkeley, is another story.
The West Camp lies southwest of the Berkeley Pit/East Camp drainage and includes the Travona, Emma, and Ophir mine workings. Just as in the East Camp, the groundwater in this area has been closely monitored since the suspension of pumping in 1982 to ensure that water levels do not rise high enough to significantly impact surrounding aquifers—in this case, 5,435 feet is the magic number.
Since November 1989, pumping operations have kept West Camp water below this level. In the late 1950’s, the West Camp mine workings were sealed off from the rest of the shafts and drifts on the Butte Hill by a series of barriers, or bulkheads—some made of wood, some cement.
Three main cement bulkheads block the connections between the Emma in the West Camp and the Original mine in the East Camp at the 1,600-foot level, and between the Emma and Colorado mines at the 1,400- and 1,000-foot levels.
Anaconda Company crews originally installed the bulkheads for two main reasons: 1) there were no plans to continue mining in the West Camp, and 2) they wanted to increase the efficiency of continuing mining operations in the other underground mines of the East Camp and the Berkeley Pit.
The bulkheads allowed the company to eventually reduce the volume of both groundwater pumped out from underground shafts and the area underground that required fresh air to be pumped in. However, even after the bulkheads were installed, water was pumped out of the West Camp Emma shaft until 1965.
When the Anaconda Company stopped pumping groundwater out of the West Camp entirely in 1965, the water level in the Travona shaft quickly climbed to over 5,500 feet. Water started seeping into Butte basements in the area bounded by Iron Street in the north, Front Street in the south, Montana Street in the west, and Maryland Street in the east (see image below).
Surface water seeps were also observed north of Centennial Avenue between Montana Street and Missoula Gulch. To reduce water levels, what became known as "Relief Well No. 21" was installed south of the Travona near Centennial Avenue.
Over the years, leakage has occurred through the underground bulkheads separating the East and West Camps, but according to monitoring data it appears that the two water systems remain mostly independent. The groundwater levels in West Camp shafts are several hundred feet higher than those in other East Camp mine workings, indicating that the bulkheads still effectively divide the two areas.
After studying the West Camp in the late 1980s, the U.S. Environmental Protection Agency (EPA) ruled that the water in the Travona shaft could rise to an elevation of 5,435 feet without threatening human health or the environment.
However, if the water were to rise above this level, EPA believes it could eventually flow untreated into Silver Bow Creek, and ARCO, the responsible party for the West Camp under federal Superfund law, would face daily fines starting at $5,000 and increasing to $10,000 after 10 days. The EPA’s concern in regard to West Camp water levels is due to the fact that these waters have elevated levels of arsenic, and thus pose a potential threat to human health.
To ensure that the West Camp water stays below that 5,435 feet mark, groundwater was initially pumped from the Travona shaft into a county sewer line and on to the Metro Sewer Plant off of Centennial Avenue. ARCO paid Butte-Silver Bow around $30,000 per month to treat this water, depending on the volume received. Treatment mainly involved reducing the water's arsenic content.
In 1998, ARCO installed a larger main pump south of the Travona near Centennial Avenue. It handles 100 more gallons per minute than the previous pump (330 compared to 230). The old Travona pump is now enjoying some downtime–it serves as a backup, used only when needed. But the old pump did its job well. For example, in September 1997, the Travona water hit 5,432 feet—just three feet below the critical mark.
ARCO diverted the West Camp water to the Lower Area One (LAO) lagoon treatment system below Centennial Avenue on March 21, 2002, incorporating this water with other LAO waters in their treatment system. The West Camp pumping system has operated almost continuously since its installation, with the only downtime being due to power outages from lightning and occasional maintenance.
The water level at the end of March 2008 was at an elevation of 5,424 feet, eleven feet below its compliance point. Since pumping began in 1989 more than 1.36 billion gallons (4,190 acre-feet) of water has been pumped from the West Camp system for treatment.
Water treatment plant working as expected
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, 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 November 2019. Any necessary upgrades would have to be completed by November 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.
Treatment technology thoroughly studied
The Berkeley Pit is literally world famous in the mine waste cleanup industry, and the final technology used in the Horseshoe Bend Water Treatment Plant, a High Density Solids (HDS) process, was selected after an assessment of tests and the demonstrated effectiveness of cleanup technologies from research groups around the world.
The Horseshoe Bend facility currently treats water from Horseshoe Bend, and will eventually be used to treat water from the Berkeley.
The treatment plant utilizes a two-stage lime (calcium hydroxide) precipitation process in combination with HDS technology. Lime, aeration and polymer addition remove metals from the water. The fully automated facility generates about 10 times less sludge than a conventional lime treatment plant. HDS technology produces denser sludge through a recycling process in which the sludge generated in the water treatment process is sent through the system many times.
The process resembles a snowball effect. Each time sludge particles are sent through, they grow in size as new particles attach to the old ones. At the end, the final sludge product – like a watery mud – is much denser.
The relatively low final volume of sludge – currently about 40,000 gallons per day in a 220,000-gallon slurry – is deposited in the Berkeley Pit, eliminating the need for a land-based sludge repository. Test results indicate that sludge disposal in the Pit may raise the pH of the water over a 10- to 20-year period, which could potentially decrease treatment costs for Pit water.
Due to the design of the system, treated water can easily be used in the concentration process at the adjacent Montana Resources mine, or, in the event that the mine ceases operations, discharged to Silver Bow Creek upstream from the confluence of Blacktail Creek and the Metro Storm Drain near Montana Street. The volume of treated water should add about 4.5 cubic feet per second (cfs) of flow to the creek, which represents about a 50 percent increase to the base flow of 10 cfs.
A performance test of the Horseshoe Bend plant was completed in November 2007, as mandated by the Record of Decision. Based on the performance review, water discharged from the plant meets all discharge standards for contaminants of concern set by the EPA. Additional adjustments still need to be made to address pH (see the article “Recent test shows plant working as expected” on this page for details). In general, plant operations are going as expected.
Montana Resources mines the water
The Past
Butte's Memory Book tells the story of Jim Ledford, a miner who lived in a log cabin below the famed Anaconda Mine. Alongside his cabin was an old dump containing scrap iron and tin cans. Mine water ran downhill through the dump, and Ledford noticed a heavy sludge formation. Out of curiosity, he had the sludge assayed and learned that it was 98-percent-pure copper.
Legend has it that Ledford told no one about his discovery. Instead, he quietly secured a one-year contract to handle the Anaconda mine water. He set up tanks, filled them with scrap metal, and ran the water through them. The undated account said his efforts earned him $90,000 that first year. His contract was not renewed.
A professional paper from a 1913 Butte mining conference tells a slightly different story. It states that in 1890 a William Ledford obtained a contract to handle water from the St. Lawrence Mine. The story ends the same, however, once the Anaconda Company realized the value of mine water, it built its own copper tanks, and copper precipitation using scrap iron became standard operating procedure. Thanks to Al Hooper for loaning his copy of the 1913 mining conference proceedings.
A third version of the story was relayed in the April 18, 1906 edition of The Montana Standard as part of a series of articles on “Queer Spots in Butte.” According to this version, in 1888 an old Welshman named Morgan who lived on the Butte Hill noticed copper dust left behind from tin cans thrown into a gully filled with runoff water from the mines. Morgan had the dust assayed and learned that it was almost pure copper. He experimented with the concept and developed a rudimentary precipitation plant, but died a few months after he had his plant operating successfully.
The story goes on to claim that a Butte Dutchman named Fred Miller dug holes in the side hill in the gulch below the St. Lawrence mine. He filled these holes with tin cans and scrap iron, allowing mine runoff water to flow over them.
For the next two or three years, he would collect the resulting copper dust every few weeks. Miller fraudulently claimed a monopoly on this system, and on several occasions tried to bluff out others on the hill who were experimenting with precipitation.
The story notes that at this point William Ledford secured a lease to the St. Lawrence water, and Miller’s heyday came to an end.
The Present
This method of copper recovery was not new: it dates back to medieval Europe. The Anaconda Company used it for years to recover copper from the water pumped from the underground mines, and the method is still used today. Montana Resources has mined copper from the rich mineral waters of the Berkeley Pit since 1998, pausing when mining operations were suspended from 2000 through 2003, then resuming in 2004. The mine pumps out roughly 13 million gallons of Pit water per day, or about 10,000 gallons per minute.
The Pit water is piped to the company's precipitation plant, built in the 1960’s next to a similar one from decades earlier. The water flows into concrete cells filled with scrap iron, and then chemistry takes over. Simply put, the iron in the cells and the copper in the water trade places. The water is returned to the Pit with a higher iron content, and the copper precipitates, or solidifies out of solution, clinging to the remaining iron.
The chemical reaction does not take long. Water stays in contact with the iron for only about an hour, and then it flows back into the Pit through a separate ditch along the old Horseshoe Bend channel, which can be seen from the viewing stand as the waterfall on the northeast rim of the Pit. Mine officials say that this constant circulation process should not affect the water level of the Pit, nor should the change in water chemistry have an effect on eventual water treatment operations.
Once per week, crews drain each cell to recover the precipitated copper. A front-loader scoops up the copper and scrap iron mixture and transports it to a vibrating screen. Water sprayed from high-pressure hoses knocks the copper through the screen into a tank below. Remaining iron goes back to the cells for reuse. The cement copper concentrate is then shipped to the concentrator and processed through a filter press to reduce the water content for rail shipment. By pumping water from the Berkeley, the company recovers about 400,000 pounds of copper per month.
The company also routed copper-rich Horseshoe Bend water through the precipitation plant from 1998 until the mine shutdown of 2000. The sale of this precipitated copper helped to offset water treatment costs. Once through the precipitation plant, Horseshoe Bend water was mixed with lime (calcium hydroxide) and pumped north to the Yankee Doodle Tailings Pond. Since the treatment plant went online in 2003, this Horseshoe Bend water has been kept out of the precip plant circuit.
The equation below shows the main chemical reaction that takes place during the copper precipitation process:
Fe + CuSO4 becomes FeSO4 + Cu
Seasonal bird mitigation efforts ongoing
After several highly publicized incidences of bird deaths at the Berkeley Pit, a popular myth arose: migratory waterfowl are instantly killed if they land on water in the Berkeley Pit. In fact, hundreds of waterfowl land on the surface of the Berkeley Pit every month during migration seasons, and they typically fly off unharmed within a few hours, either on their own or through Montana Resource's hazing activities, also known as the waterfowl mitigation program. The 2002 Consent Decree recognizes that "birds exposed to Berkeley Pit water for less than 4-6 hours should not be at substantial risk." If a bird is observed suffering from the effects of water toxicity, it is netted and brought on board the houseboat used to patrol the Pit lake. The bird is placed in a 5-gallon bucket of fresh water and brought to shore. It is then transported to a veterinarian or released into fresh water at the north end of the Yankee Doodle Tailings Pond; tailings particles settle out on the south portion of the pond, leaving clear, alkaline (or non-acidic) water in the north end which mixes with snowmelt runoff from upper drainages, resulting in very low concentrations of dissolved metals.
In November 1995, a flock of snow geese landed on the Pit lake. After several days of stormy weather and fog, 342 birds were found dead. In response to this incident, the two responsible parties for the Pit under federal Superfund law, Montana Resources and British Petroleum-Atlantic Richfield, also known as BP-ARCO, implemented a waterfowl mitigation plan, which was approved by the EPA and other agencies in May 1998. This program is aimed at locating waterfowl in the area and then inciting the birds to fly away. An observation station was set up overlooking the Pit area. This station is an enclosed building equipped with spotting scopes and spotlights for night viewing to locate, count and identify species of waterfowl on the Pit lake.
Montana Resources’ personnel make hourly observations for birds during the spring and fall migrations, while the pit is not frozen, and cut back to 5-6 observations per day during non-migratory seasons. A variety of devices are used to chase birds off the water and out of the Pit. From the observation station near the southeast rim of the Berkeley Pit, Montana Resources’ personnel use rifles and shotguns to scare birds into the air.
In addition, three Phoenix Wailers – high-tech devices that emit predator and electronic sounds – are located near the surface of the Pit lake to discourage birds from landing. A 22-foot houseboat, docked near the pump barge, is used for periodic excursions on the water to haze waterfowl that ignore other warnings. Not all types of birds react to hazing. Typically, most ducks, geese and swans will react immediately to the noises. Diver birds such as grebes and loons tend to go underwater as a natural defense mechanism when they are alarmed.
Normally, if birds are not hazed or disturbed, they leave the Pit area at nightfall. If a dead bird is found on the water or near the Pit, then the US Fish and Wildlife Service is contacted. They decide if an autopsy is necessary.
From 1995 through 2004, 75 birds were found dead. The advances made to deter migrating waterfowl from landing on the water or staying on the Pit appear to be working. Thousands of birds land and are hazed off of the Pit each year. Though many local authorities decided that the 1995 incident was isolated and not likely to happen again with the safeguards that are in place, in October 2007, 37 birds, including ducks, geese, and one swan, were found dead at the Pit after a weekend of fog. It is unclear why mitigation activities failed to haze these birds away from the site, although the weather was almost certainly a factor. As the mitigation program continues, all involved continue to work to keep such incidents to a minimum.
Above the Pit: The Yankee Doodle Tailings Pond
North of the Berkeley Pit stands one of the largest earthen dams in the United States. The dam, constructed from waste rock mined out of the Berkeley Pit, stands over 650 feet (200 meters) tall. It holds back the Yankee Doodle tailings impoundment, also known as the Yankee Doodle Tailings Pond. As part of active mining operations, Montana Resources pumps tailings and water to the Yankee Doodle Pond. Lime rock is also added, resulting in a non-acidic pH (above 7.0) tailings slurry, thus mitigating or avoiding the phenomenon of acid mine drainage.
Tailings particles settle out on the south portion of the ponds. Snowmelt runoff from upper drainages also mixes with the water at the north end of the pond. These factors result in clear water with an alkaline (or non-acidic) pH and very low concentrations of dissolved metals at the north end of the pond.
When mining operations were suspended from 2000 through 2003, water was no longer pumped to the Yankee Doodle site, and the tailings deposited there began to dry out. In response to concerns from the community over dust clouds blowing in the vicinity of the tailings pond, Montana Resources spread about 1.5 million tons of rock, approximately 18 inches deep, over about 506 aces at the tailings impoundment site to keep the dust down. Since the mine reopened, the tailings deposit has remained wet, resulting in no further instances of tailings-dust clouds on Butte’s northern horizon.
Many are learning from Berkeley Pit
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.
Pit viewing stand is newly renovated
What if an earthquake were to strike?
There are several reasons why we don’t need to be overly concerned about the Pit in the event of an earthquake, including the fact that there has been no significant seismic activity in nearby faults during the 28 years that the Earthquake Studies Office has been monitoring the area.
In the mining region, the recorded seismic activity is mainly caused by a few mining blasts per week, however, two landslides in the pit have been recorded in the last 28 years and a few very small, non-mining related earthquakes are recorded within Butte Silver-Bow county annually. Most seismic activity in Montana occurs outside of Silver-Bow County, and in the worst-case scenario, a large earthquake could cause landslides or sloughing in the Pit, but would not cause the Pit to overflow. Such an earthquake would cause considerably more damage to buildings and structures in the Uptown area than to the landscape or Pit.
After the initial PITWATCH article on earthquakes in the Spring of 2005, there was a 5.6 magnitude earthquake centered near Dillon on July 25, 2005. This earthquake was felt in Butte, but there was no evidence of any sloughing or rise in water level in the Pit.
According to the Earthquake Studies Office, there have been approximately 20 very small earthquakes within 25 km of Butte in the past year, ranging in magnitude from -.2 to 1.9. Nineteen of these were less than magnitude 1.0, and only 4 were located within Silver-Bow County. Three of these events were non-mining related events in Butte and were not large enough to be felt.
There have been no reports, past or present, of any earthquake damage to the Pit and the last earthquake greater than magnitude 1.0 in the area was a 2.8 on October 9, 2005, located 3.3 kilometers west-southwest of Butte along Silver Bow Creek.
This topic was covered in the 2005 Spring and Fall issues of PitWatch, which can be found at: http://www.pitwatch.org/2005.htm.
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.
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.
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.
Catching up with past Science Fair winners
And announcing our winners for 2009
Since 1997, the Berkeley Pit Education Committee has given awards to area students competing in annual Montana Tech Science and Engineering Fairs who use their projects to explore important topics related to the Berkeley Pit and mine waste cleanup technologies.
At the 2009 fair, three East Middle School students received awards for Pit-related projects: Jessica Robertson for her project on cementation, Katie Metesh for her project on geothermal heating, and Robin Gammons for her project on mining copper from Butte’s groundwater. Many past winners have gone on to pursue careers in science and technology.
Kels Phelps won his first Berkeley Pit awards in 2001 and 2002. Kels went on to win a Berkeley Pit award again in 2006 for his project on the metabolites produced by a microbe growing in the unique environment of Silver Bow Creek. His research involved isolating a compound produced by the microbe and analyzing its potential for medical applications. Kels was able determine the compound’s molecular structure, and found that it displayed activity in inhibiting enzyme reactions associated with various disorders such as multiple sclerosis, Huntington’s disease, and cancer metastasis.
A double-major in philosophy and religion at Pacific Lutheran University in Tacoma, Washington, Kels is currently completing a semester studying abroad in Trinidad and Tobago. He feels that his experience doing research in the Butte area has served him well.
“The opportunities that I was able to take advantage of, specifically due to the Berkeley Pit and the Upper Clark Fork, provided excellent intellectual stimulation and helped me prepare for college.”
Emily Munday won Berkeley Pit awards in 2000 and 2003 for her projects studying mining’s impact on Silver Bow Creek using aquatic insects as bioindicators of stream health. She delved deeper into Silver Bow Creek water quality by analyzing parameters such as pH; conductivity; copper concentrations in sediments, insects and water; and nutrient levels.
“I ultimately learned that copper mining has negative impacts on stream health, something that many Buttians know,” Emily stated when asked to reflect on her experience with the science fair. “However, I also learned that after remediation, Silver Bow Creek is recovering and can someday be very similar to what it was historically – before Butte's mining days. If we continue to care for it, and locate and block or treat ongoing pollution sources like metals runoff from the hill and eutrophication from the waste water treatment plant, Silver Bow Creek will recover and be the trout fishery it once was.”
Emily currently attends Boston University, where she is busy earning a degree in marine science. As part of her studies, she traveled to Belize for a coral reef study. Last summer she interned with the Water Environment Federation at the national headquarters in Alexandria, Virginia, helping with the national Stockholm Junior Water Prize competition. This summer, she has a research grant to assess coral reef health in marine protected areas in the Caribbean. She also swims for the BU Terriers, which she describes as her “20-hour per week part-time job.”
“Studying impacted areas in my hometown and learning that there is hope for recovery made me want to use science to protect beautiful places. I am studying marine science because the ocean is an important source of biodiversity, food and oxygen production, and beauty. I want to help people learn about it so we can save it.”
Alexandra Antonioli was a recipient of a Berkeley Pit award in 2002 for her project investigating whether modification of a native Berkeley Pit microbe could be used to enhance the organism’s ability to bind heavy metals. Researchers at Ohio State University had modified an algal strain so that it could bind metals such as cadmium from contaminated soil. Alexandra’s goal was to insert the same gene used to modify the algae into a native Berkeley Pit yeast species. Initial results with the newly modified yeast were promising, but more research is needed to determine the full impact of the organism.
Alexandra graduated from Yale University in 2007 with a B.S. degree in Biophysics and Biochemistry. After graduating she worked full-time as a research assistant in Professor Scott Strobel’s laboratory for two years. Her research investigated an RNA structural motif called the K-turn in the Azoarcus group I intron. This type of advanced research involved structural biochemistry and crystallography.
In August 2009, Alexandra will enter the University of Colorado’s Medical Scientist Training Program where she will earn dual M.D. / Ph.D. degrees. She looks forward to being closer to Montana and is excited for a career in academia as a physician scientist.
“My interest in research started with science fair and the research with the Berkeley Pit. I was fortunate to find mentors like Professor Andrea Stierle and Professor Grant Mitman who encouraged and helped me gain valuable research skills. I think that their excitement about research helped inspire me to study science and continue with research throughout college.”
Today Alexandra considers the Berkeley Pit from a scientific perspective. “As a scientist, I view the Berkeley Pit as a place for exploration and discoveries. Andrea and Don Stierle’s lab has shown that numerous compounds can be isolated from Berkeley Pit waters that have potential antibiotic and anticancer properties. This type of research is extremely challenging because it may take years to isolate, develop, and characterize one compound. However, the rewards of finding a new compound with the drug potential to help thousands of lives are immeasurable.”
To describe her hometown to people in Boston, Emily still refers to the Berkeley Pit with a kind of stubborn pride. “I think that when it is cleaned up, we still need to remember what it looked like so we can use it as an example of how humans can change and destroy a landscape so we don't make similar environmental mistakes in the future.”
Kels offers a similar view of the Pit, acknowledging the good and the bad. “I think that the Berkeley Pit is the result of some very serious mistakes, and I am a hearty proponent of efforts to contain the damage, and eventually try to restore it, in some way, to some semblance of naturality. I also find it very encouraging to know that, even from such a huge environmental crisis as this, there are positive discoveries that can be made. The compound isolated in my 2006 research doesn't even begin to scratch the surface of the potential for novelty that lies in the Berkeley Pit. As long as we have to live with it, we must continue to use it in this way.”
This is one of the most common questions asked about the Pit, and fortunately the short answer is no.
The likelihood of the Pit ever overflowing is very, very low. The 1994 Record of Decision and 2002 Consent Decree established the maximum level that the water will be allowed to reach to ensure that the Berkeley Pit is lowest point in the cone of depression (refer to the Pit Water Level graphic).
Wells have been established to monitor water levels. Failure to keep the water below the 5,410-foot mark would result in steep fines for BP-ARCO and Montana Resources. The Horseshoe Bend Water Treatment Plant is already in-place and operating. It has the capacity to treat water from the Berkeley Pit when it becomes necessary. This will ensure the water level remains below 5,410 feet in perpetuity.
Finally, if for some unforeseen reason the water level in the Berkeley Pit was allowed to rise unchecked, the water would still never overtop the rim of the Pit. The groundwater flow would eventually reverse direction and, instead of flowing toward the Pit, as it does now, the water would begin to flow away from the Pit into the void spaces between the sand grains in the alluvial aquifer.
This underground water movement would prevent the Pit surface water from ever approaching the rim. Given the federal orders, potential fines, and frequent monitoring activity, the water will not be allowed to rise unchecked.
Here are a few other common questions and answers:
What is the current water level of the Pit?
As of April, 2009, the Pit's water level was 5,280.29 feet above sea level. The water level climbed about 7.35 feet since March 2008. Since June 1996, when PitWatch was first published, the water has risen about 152 feet. The rate of rise has been decreasing over time, and should continue to decrease in the years ahead as the widening circumference of the upper part of the Pit collects the water.
Is the water level in the Pit rising according to predictions?
The most recent evaluation of monitoring data confirms previous predictions that it will be approximately 2023 when water levels will approach the critical level of 5,410 feet above sea level. The current model and prediction assumes the amount of water flowing to the Pit will stay fairly constant – enough water to raise the level in the Pit about six to eight inches per month.
Also, data indicate that the water level at the Pilot Butte shaft is the highest among all the monitoring points in the program. As shown on the timeline (pages 8-9), a design assessment must be completed four years before the water level in any of the designated wells or shafts is expected to reach 5,410 feet and the treatment plant must be ready to operate two years ahead of time. This timeline is reviewed and evaluated every year and updated as needed. Note that water levels in the Pit have been rising more slowly than predicted in the 1994 Record of Decision.
How is the Horseshoe Bend Water Treatment Plant operating?
The treatment plant treats an average of about 3.4 million gallons of water per day. This water currently comes from the Horseshoe Bend flow. All treated water is used in mine operations, and the residual sludge from the treatment process is returned to the Berkeley Pit at a rate of 250,000 gallons per day. No water is discharged off of the site.
A performance test of the Horseshoe Bend plant was completed in November 2007, as mandated by the Record of Decision. Based on the performance review, water discharged from the plant meets all discharge standards for contaminants of concern set by the EPA. Additional adjustments still need to be made to address pH (see page 10 for details). In general, operations are going as expected.
Will the Horseshoe Bend Water Treatment Plant empty the Berkeley Pit?
No. In the 1994 Record of Decision, the agencies involved decided that it would be unfeasible for the Potentially Responsible Parties (PRPs) to ever completely empty the Berkeley Pit. The remedy selected for the Berkeley Pit is to treat all water inflows to maintain the level below 5,410 feet above sea level.
Would changes to the national Superfund program affect the operation of the Horseshoe Bend Water Treatment Plant?
No. The Berkeley Pit site is the responsibility of BP-ARCO and Montana Resources. Thus, the plant will not be affected by any changes to the EPA's Superfund program. The legally binding Consent Decree, which was signed by the responsible parties in 2002, established the financial commitment to operate and maintain the water treatment plant in perpetuity.
What is the waterfall on the northeast wall of the Pit?
Historically, the waterfall was created by the Horseshoe Bend flow north of the Berkeley Pit, but that water is now treated and used in Montana Resources mine operations. Since February 2004, water returning to the Pit from the "precip plant" forms the waterfall.
The waterfall flowing down the northeast wall of the Berkeley Pit is highly visible from the Viewing Stand. Historically, the water came from the Horseshoe Bend drainage, but now it is Pit water returning after having been run through the precipitation plant where copper was removed. (Photo by Josh Peck)
This issue was prepared with assistance from the Clark Fork Watershed Education Program, www.cfwep.org.