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.
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.
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.
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.
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 engulf, 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 industrialized form of mining, also meant fewer jobs for the city’s miners. But mining had always been the lifeblood of Butte, and so the community embraced the new mine, and there was little objection to the sacrifice of some of the city’s neighborhoods.
The Anaconda Company’s decision to begin open pit mining in Butte was not without its reasons. In 1955, copper prices were the highest they had been since the end of World War I in 1918. And the following year, 1956, would mark the highest copper price seen until 2006 (with the exception of the lone year 1974, when copper briefly spiked due to an end to price controls and the ongoing demands of the Vietnam War).
Those high prices gave the Company a big incentive to rethink its Butte operations. The most accessible parts of the Butte hill had already been mined out. Legend has it that Marcus Daly’s original ore vein was 30% copper. That is extraordinarily rich ore, and the veins of that quality could not last- as a point of comparison, when it opened, the ore mined at the Berkeley was about 0.75% copper, and the ore being mined at Montana Resources nearby Continental Pit operation today is approximately 0.25% copper. In order to economically extract copper from lower grade ore, the Pit was born.
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.
In the Berkeley Pit, samples are taken from anywhere between three to 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 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.
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.
Quality: HD Title : Be Afraid Release : 2017-04-01. Language : English. Runtime : 99 min. Genre : Thriller, Science Fiction. Stars : Brian Krause, Kevin Grevioux, Louis Herthum, Jaimi Paige, Callie Thorne, Jared Abrahamson.
Not long after John Chambers and his family arrive at their new home in a small country town of Pennsylvania, John begins to experience sleep paralysis. Lying there paralyzed, trapped within his own nightmare, other-worldly beings visit John. They are entities which exist in the darkest shadows of the night and can only be seen out of the corner of one’s eye. These encounters begin to haunt John, transforming to complete terror as he discovers the entities’ sole purpose… the abduction of his seven year old son. In the end, John will uncover the town’s horrific secret, a portal on his land, and make one last attempt to save his son before the shadow people permanently take him away to their world.
The Berkeley Pit will never overflow. In 1994 the EPA established the Critical Water Level (the maximum level the water will be allowed to reach) at 5,410 feet above sea level, which is one hundred feet below the rim.
Water levels are regularly monitored at the Pit, in historic underground mines, and in wells surrounding the Pit. Failure to keep the water below 5,410 feet would result in steep fines for the companies responsible for the site, BP-ARCO and Montana Resources.
In addition to careful monitoring, the Horseshoe Bend Water Treatment Plant was constructed to make sure water in the Pit remains below 5,410 feet. Pit water will be pumped, treated, and discharged when the level nears the critical point.
Even if the water was allowed to rise unchecked, it would still never reach the rim. The groundwater flow would reverse direction and, instead of flowing toward the Pit, as it does now, the water would flow away from the Pit, underground into the sandy aquifer beneath Butte’s valley.
Due to the underground flow, Pit surface water would never reach the rim. Considering the federal orders, potential fines, and frequent monitoring, Pit water will not rise unchecked.
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.
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 until a Pit slough in 2013 knocked out the necessary pump. The mine pumped out roughly 13 million gallons of Pit water per day, or about 10,000 gallons per minute.
In copper precipitation, 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 could 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 recovered 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.
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.
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.
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.
A 5.6 magnitude earthquake centered near Dillon on July 25, 2005 did not affect the Berkeley Pit. There was no Pit wall sloughing or change in the water levels in the Berkeley Pit, the underground mine shafts, the alluvial aquifer wells, or the majority of the bedrock monitoring wells.
However, two bedrock monitoring wells (A&B) showed changes. Well A showed an initial water level decline of about one (1) foot after the earthquake, and the level stayed lower for a number of days before rising again. Well B, which is located in an area that wasn’t dewatered as extensively by historic mining activities as other portions of the bedrock aquifer had a 9-foot drop in water levels in the month following the earthquake. Recently, the water elevation in Well B is rising again.
One possible explanation for the lower water level in these wells is that the earthquake opened up existing fractures in the bedrock surrounding the wells. Water then flowed into these fractures until the bedrock adjacent to them became saturated. When that happened, the water levels began to rise again.
Since the July earthquake, there have been two additional quakes in the region, one of which was centered in the Butte Basin. Both of these other quakes were considerably smaller in magnitude, and no effects were noted in the Berkeley Pit or bedrock monitoring wells.
The community has many common misconceptions about the Berkeley Pit. This section addresses a few of those most often heard false statements.
Migratory waterfowl are instantly killed if they land on water in the Berkeley Pit.
Hundreds of waterfowl land on the surface of the Berkeley Pit every month during the migration season, and they fly off within a few hours, either on their own or through MR’s hazing activities. The 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 Berkeley Pit. 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 Yankee Doodle Tailings Pond.