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Bingham Canyon Mine – The World’s Deepest Open Pit Mine

Despite what you’ve probably heard from misinformed but well-meaning friends, parents, teachers and/or coworkers, according to actual astronauts, the Great Wall of China isn’t visible from outer space, at least to the naked eye.  

In fact, few of earth’s natural and manmade structures are, but some like the Grand Canyon, the great pyramids of Egypt, and the Amazon River can be seen from the heavens. 

Surprisingly, so can Utah’s Bingham Canyon Mine, or as it’s more commonly known to locals, Kennecott Copper Mine.  

Located just a stone’s throw southwest of downtown Salt Lake City, the Bingham Canyon Mine isn’t exactly a household name like the aforementioned marvels, but it is the world’s largest open pit mine.

More than 2.5 miles (4 km) across from rim to rim and plunging nearly 4,000 feet (1,200 m) below the earth’s surface, it’s owned by British-Australian natural resources conglomerate Rio Tinto Group, and the expansive facility has its own concentrator plant, refinery and smelters too. 

Since large-scale operation began in the early 1900s, it’s estimated that the mine has produced as many as 20 million tons of copper, more than any other mine in the world. 

But though its claim to fame is copper, the region’s ore is also rich in gold, silver, molybdenum and other precious resources, the collective annual value of which regularly exceeds that produced by any other mine. 

That said – big shocker  – large scale industrial mining is a particularly dangerous and environmentally unfriendly endeavor. 

Over the years the mine has experienced numerous accidents and mishaps, as well as more than a few events in which huge amounts of various toxins have been released into the region’s air, land and water. 

Worse yet, some claim that the most egregious episodes may not have been accidents at all, and that they’ve been going on behind the scenes for decades. 

Whatever the case, the Bingham Canyon Mine is a premier example of man’s unstoppable drive to dominate the environment, which sadly, often leads to the destruction of it as well. 

Now, the Bingham Canyon Mine.

History

Valuable minerals and precious metals were discovered in north-central Utah in the 1840s by brothers Thomas and Sanford Bingham, after whom the canyon and mine would eventually be named. 

The pair diligently reported their findings to Brigham Young, who just a few years later would succeed Mormon founder Joseph Smith as president of the Church of Jesus Christ of Latter-day Saints.  

But though Young recognized the immense wealth trapped in the region’s ore, at the time protecting settlements from hostile locals who considered Mormonism a dangerous cult was a far more pressing concern. 

When the Mormons packed up and moved to greener pastures in neighboring Weber County shortly thereafter, the resources were largely forgotten until two decades later, when a number of claims were filed and mining began in earnest. 

However tests indicated that the ore contained just 2% copper, and extracting it from the hard rock in which it was encased was prohibitively time consuming and expensive. 

Hence, most miners generally ignored copper and focused on gold and silver. 

For most of the 19th century, area mines were small affairs run by bedraggled families and gritty prospectors, most of which did little more than eke out meager livings in the harsh and unforgiving climate. 

A few did get rich, but it wasn’t until the turn of the century that large-scale open-pit mining began. 

In 1896 Samuel Newhouse and Thomas Weir acquired a number of claims, after which they formed the Boston Consolidated Gold and Copper Company.

The pair enjoyed success mining both copper and gold, but they eventually sold out in 1904 to new owners determined to increase efficiency and profits by investing heavily in mechanization and modernization. 

Despite a huge initial investment their gambit worked, and by 1912 the facility was the world’s largest industrial mining complex. 

Expansion and modernization continued at a breakneck pace, and by the 1920s nearly 20,000 workers from all over the world labored in and around the mine. 

Most lived in company-built shantytowns constructed in remote canyons nearby, but especially for immigrants and unskilled laborers, conditions were often deplorable.  

Outbreaks of diseases like cholera and typhoid were common, and in addition to long hours, the harsh climate, and low-quality food and water, mortality rates were high. 

However as mining techniques improved and the operation became even more mechanized, the workforce dwindled. 

Nearly a half century later in the ‘80s the number of workers had been reduced by more than 75%, and of the hundreds of small claims, nearly all had been bought up by two big players – Kennecott and the Anaconda Minerals Company. 

Due largely to rising labor and energy costs and unstable commodity prices, the ‘80s and ‘90s were characterized by multiple closures. 

The mine was first sold to BP Minerals and later to Rio Tinto, the latter of which undertook yet another massive modernization program beginning in 1989 that ultimately cost more than 2 billion USD in today’s money.   

The mine’s outdated 1,000+ car railroad network which had faithfully transported thousands of tons around the site every day for decades was scrapped in favor of a system of conveyors and pipelines that together reduced operating costs by more than 25% and returned the operation to profitability. 

Without getting into the geological “weeds,” Bingham Canyon’s ore is largely composed of copper deposits contained within massive quartz veins that have pushed their way up and through the sedimentary rock strata over millennia. 

Made up of multiple zones, the site is characterized by a central magnetite core surrounded by concentric layers of ore containing copper, gold, silver, molybdenum, zinc and lead.   

Recovery and Production

From the bottom of the crater and the stepped terraces protruding from the mine’s towering walls, ore is blown into manageable chunks using explosives deposited inside deep boreholes. 

After epic blasts that release thousands of tons of overburden, the newly freed material is loaded into massive 3,000+ horsepower diesel haul trucks that carry more than 200 tons to the surface at a time. 

Next, the material is transported via conveyor approximately 3 miles (4.8 km) to Magna, Utah where it’s pulverized by large crushers called concentrators.  

Then, the various components including copper, gold, silver, lead, molybdenum, platinum and palladium are extracted by flotation, leaving behind gobs of useless slurry called gangue which is deposited in large tailings pits. 

The valuable concentrate is then whisked to the smelter about 18 miles (29 km) away, where it’s dried and injected along with oxygen into a 2,370 °F (1,300 °C) flash furnace. 

The smelting process releases impurities that are skimmed off in the form of slag, though other byproducts like sulfur dioxide aren’t considered waste, since it can be turned into sulfuric acid, of which the mine produces about 1 million tons annually. 

The remaining copper still contains about 30% impurities by weight, but after another round of smelting it’s nearly 98% pure. 

At this stage the copper is cast into 700-pound (320 kg) plates that are transported by rail to the finishing refinery where they’re submerged in huge vats of acid. 

When electricity is run through the solution the anodes dissolve slowly, and the suspended copper – now 99.99% pure – redeposits itself on hanging cathodes. 

Remaining impurities are then removed and trace amounts of precious metals like gold and silver settle to the bottom of the vats where they’re recovered by chemical processes and smelted in induction furnaces.  

These days the mine employs approximately 2,500 workers that process more than 400,000 tons of material daily.  

The mine runs around the clock 365 days a year, and on average 500 workers are present during the day, while about 350 work the night shift.  

Annual copper production typically tops 400,000 tons, or between 8 and 12% of the United States’ domestic yearly consumption. 

Environmental History

Though the mine’s environmental woes date back much farther, they largely came to light in the ‘80s and ‘90s when much of the area’s groundwater was found to be contaminated with lead and arsenic, and it didn’t take much to figure out that they’d come from the nearby mine.

But though these contaminants had been accumulating in relatively small quantities for nearly a century, they were now present in dangerously high concentrations. 

Clean up had been an ongoing process, but efforts took on a new urgency in 1994 when the Environmental Protection Agency (EPA) proposed including a southern portion of the mine on its Superfund National Priorities List. 

For those not familiar with the term, the federal Superfund program was founded in 1980 to classify and clean up the country’s most contaminated sites.

Needless to say, this classification would have been embarrassing and bad for business, and it would have exposed the mine’s corporate owners to unimaginable liability.  

Rio Tinto successfully avoided the dreaded “Superfund” designation, and as a result the company was able to sidestep many regulatory actions and sanctions by voluntarily cleaning up a large portion of the mess it had created.  

By some estimates, since the early ‘90s the company has spent more than 400 million USD and secured more than 25 million tons of waste, though detractors claim that their efforts are a drop in the bucket compared to what needs to be done. 

Even as far back as 1904 sulfur dioxide emissions were blamed for significant crop damage among local farmers. 

To set things right, the following year they collectively filed a class action suit against the mine’s owners in the US District Court of Utah. 

In 1906 a federal judge awarded them damages and ruled that ore containing more than 10% sulfur could no longer be smelted, and as a result production slowed dramatically. 

Then less than a decade later in 1912, both private and government organizations raised alarms about a new threat – high levels of asbestos. 

Used primarily as insulation, as asbestos aged and dried it released minute particles into the atmosphere that were inhaled and came into contact with exposed skin, causing everything from fibrosis and lesions to mesothelioma and arterial hardening.

But though asbestos was a huge problem for Kennecott Corporation long before Rio Tinto bought the mine, even darker days were on the horizon as public awareness of environmental issues increased after Rachel Carson’s book Silent Spring was published in the summer of 1962. 

Despite these legal and public health woes however, in 1966 the mine was designated a National Historic Landmark under the name Bingham Canyon Open Pit Copper Mine. 

During the ‘70s and ‘80s additional environmental issues came to light, after which a number of state and federal regulatory agencies filed suit. 

The EPA estimated that more than 70 square miles (180 square km) of the once pristine Oquirrh Mountains were now hopelessly contaminated after decades of leaks, spills and runoff. 

The pollution was so bad that many of the small creeks in surrounding canyons were perpetually choked with foamy “yellow boy” that gave the area an eerie otherworldly appearance. 

Then in 1988, state engineers and inspectors determined that the town of Magna faced imminent annihilation from an immense pit containing more than a billion tons of toxic slurry that were held in place by an inadequate dam-style retaining wall that was likely to fail during the next earthquake. 

In fact in recent decades there have been nearly a dozen earthquakes in the vicinity, some of which measured nearly 3.5 on the Richtor scale and were centered just a few miles from Magna. 

A number of mitigation strategies were proposed, and the company ultimately spent nearly 1 billion USD reinforcing the pit, but though a looming tragedy was averted, critics pointed to the cozy relationship between company executives and regulators that kept the magnitude of the situation out of the limelight.  

Throughout the ‘90s the company paid a number of outwardly hefty fines related to its environmental misfortunes, but based on annual revenue most amounted to little more than polite slaps on the wrist, despite the fact that by some estimates, the mine’s toxic runoff may have killed more than 25% of the fish, birds and amphibians in the vicinity, and caused untold human suffering, much of which wouldn’t be fully realized until decades later.   

These days the long-term effects of the underground water supply contamination have taken on new importance as the populations of Salt Lake City and its suburbs continue to grow. 

In all likelihood, residents and governments of Utah’s largest cities will be forced to resort to reclaiming surface water as water use increases. 

Chemical spills have always been a major component of the mine’s environmental impact, and it’s often claimed that though many incidents are reported, many more are swept under the proverbial carpet.  

In recent years, some of the most notable include a 1.3 million-gallon sulfuric acid spill in 2000, and 240,000-gallon arsenic and lead spill in 2003, and another 160,000-gallon sulfuric acid spill in 2010. 

And then there are the landslides…

On the morning of April 10, 2013, approximately 165 million tons (2.5 billion cubic feet or 925,000 cubic meters) of earth dislodged and thundered into the bottom of the pit in what may have been the largest non-volcanic landslide in recent North American history. 

Thankfully there were no injuries or deaths, thanks to a state-of-the-art radar system the company had previously installed to monitor ground stability. 

The investment paid off, giving engineers and safety personnel ample time to evacuate both workers and equipment before the incident.

However the immense clean up effort severely curtailed production, and since then a number of smaller landslides have occurred, including one in mid-September of 2013, and another in late May of 2021, neither or which were as large as the one in 2010.  

2030s and Beyond

The Bingham Canyon Copper Mine by Doc Searls is licensed under CC-BY

Rio Tinto recently applied for permission to expand its largest tailings pond by as many as 700 acres. 

And yes, this is the same tailings pond that was dangerously close to inundating Magna just a few years back. 

Though already filled to capacity with chemical laden tailings, if approved by the company’s board and state and federal regulators, the project would pave the way for at least another decade of operation. 

According to some sources, the mine may stay open well into the 2030s, after which what remains may be prohibitively expensive to extract. 

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