That's Some Pile of Rocks

Visiting the World's Largest Open-pit Copper Mine, Kennecott Utah Copper

View from Visitor Center

You would not be reading this story were it not for copper. Without copper you wouldn't have electricity to power your computer - and you probably wouldn't even have a computer. Lights would be hard to have, as would an oven to heat dinner, an engine to make the truck go, turbines to produce electricity, batteries to power flashlights. All those take copper, or one of its genetic offspring, bronze and brass. Copper is versatile, strong, easily pounded and stretched and shaped to endless applications, it resists corrosion and is a good conductor of heat and electricity. Everyone, in short, uses copper.

Of course, all that copper has to come from somewhere, and chances are pretty good that if you could trace the copper in your life back to one geologic spot, it would likely be "The Pit," formerly called "The Hill," a hole in the Oquirrh Mountains southwest of Salt Lake City so huge it can be seen from space and one which has, over the last century, been the world's most productive producer of the metal.

The Pit, and the towering slag piles that surround it, slumbers on the western horizon, visible from every part of the Salt Lake Valley. It is undeniably huge - in winter it can be snowing on the top of the pile and spring-like on the bottom - so huge that its scale is difficult to comprehend. Here goes: 4,000 feet deep and 2.5 miles wide, filled with mammoth dump trucks and cranes which only appear to inch across the terrain like tiny bugs.

Another Pile of Rocks Since mining here began in 1906 more than six million tons of copper have been produced, along with vast quantities of by-products like gold and silver and molybdenum. And since 1992, more than a million visitors have walked up to the edge of the mine and peered in.

Not an Easy Way to Get Rich

About 18 million years ago as the Great Basin - the rough country between Salt Lake City and Reno - was being stretched and pulled, mountains thrust up along geologic faults and valleys lowered. In the middle of one of the ranges a huge vein of copper thrust towards the surface in the form of a 9,000-foot high mountain.

Back in 1848, three guys by the name of Bingham - father Erastus and sons Sanford and Thomas - were grazing cattle in the central part of the west slope of the Oquirrhs and accidentally discovered what they thought were copper-bearing ores. They showed the ores to Brigham Young, who was then the Mormon church prophet and territorial leader, but Brigham Young told the men to concentrate on grazing and forget about the rocks. A few years later, in 1860, an Army colonel by the name of Patrick Connor sent some men into the Oquirrh Mountains near where the Bingham men had grazed. The men found the same metal-bearing ores. Connor set the men to work, helping to kick off what would become a huge rush for minerals.

Free Rocks! By the 1870s narrow Bingham Canyon was crowded with homes and shops supporting thousands of men who trooped daily into tunnels which snaked into "The Hill" and the surrounding mountains. By the turn of the century as many as 20,000 people of 40 different nationalities lived and worked in the communities spread along the canyon. Like many places in the West, it was the influx of mining labor that helped bring about a surprising ethnic diversity.

At first, miners sought ores by riding rail cars into mining tunnels, dynamiting the rock, and then dumping the ores into the rail cars and sending it all back out. Then about the turn of the century some brilliant young metallurgical engineer figured out it would be easier to get to the rock by simply slicing the mountain apart. Rather than tunnel in to The Hill, huge machinery began to, scoop by scoop, pull the mountain apart. The Pit was born.

In 1903 the canyon's miners were consolidated into the Utah Copper Company, which in 1936 became the Kennecott Copper Company. Since the 1940s large expansions and advancements have gradually upped the mine's effectiveness and wealth.

Six Easy Steps to Get Copper!

Today, the process of extracting small amounts of copper from large amounts of rock is funner to watch than to read about. But for the die-hard curious, here is a condensed version:

  • Geologic scientists chart the present and future boundaries of the pit and gauge which layers of rock have the richest deposits. Every aspect of the mine is carefully planned and analyzed well in advance of any actual mining.
  • Ammonia nitrate explosives drilled into the mountain help to loosen bedrock. After the charges explode massive shovels, capable of lifting out over 90 tons of rock in each bite, cut into the mountain and load the ore on gargantuan dump trucks with ten-foot tall tires. The trucks are capable of carrying 240 tons of rock at once.
  • The rocks are sent on a five-mile conveyor to the Copperton Concentrator where they are reduced to pieces about the size of a basketball, then sent about 15 miles north to another concentrator.
  • In a semi-autogenous grinder mill the rocks are ground into half-inch diameter bits, and later into a fine powder.
  • The powder goes into a 3,000-cubic foot cell where air and reagent are injected into the mixture to form a bubbly froth. Molybdenum, a steel-hardening alloy, is separated from the mixture, which is sent on to the smelter.
  • In the smelter, iron, gold, silver and sulfur are pulled out of the mix and the copper concentrate is heated to produce molten copper. The molten material is quenched with water, slowly cooled, the sent to another furnace where more sulfur is extracted. Finally, for ten days, electricity is run through the copper to produce a 99.9 percent pure block, which is sold to customers. Different facilities handle gold and silver, which are produced in tiny but very valuable quantities. The waste rock is dumped onto an enormous tailings pile near Interstate 80 and the Great Salt Lake.

Copperton Recent upgrades to the Kennecott facility has made this facility the cleanest, most efficient copper producer in the world, the company says.

Environmental Quandary

All this wealth, of course, does not come without a price. The early decades of the mine were especially hard on the environment. Hillsides denuded of trees sent flashfloods into the valley. Contaminants crept into the groundwater. Scoured slopes became an ecological wasteland. Smoke from the smelter, especially sulfuric smoke, blanketed the Salt Lake Valley with a choking smog. And today, because of the enormous quantities of 'waste' rock the company hauls off the mountain, the U.S. Environmental Protection Agency has labeled the mining company one of the nation's largest 'polluters.'

But in as many ways as open pit mining has scarred the land, Kennecott has worked to heal it, too. In the 1960s the company began an aggressive seeding program in the Oquirrhs, and billions of dollars spent beginning in the 1970s helped to clean the air and clean and conserve the water. The company owns almost half of the entire Oquirrh range, with peaks reaching above 10,000 feet, and sound environmental management has made the range an Eden of wildlife and biological diversity.

A View from the Top I would rather look at a mountain than a huge human-made pit, but at the same time I realize the need for copper and what it gives to me. Standing at the mining visitor center, looking south at the serrated walls of the mine, I am amazed at the algebraic structure of the pit. From the summit of West Mountain, far above the mine, I can not honestly look down at the pit and say it is not a beautiful thing. It is beautiful, in an odd way, not just for its color or its lines, but also for it sheer mass and volume. And it is beautiful, too, in scale, for it is what we have built to help run society.

Seeing the hole:

From downtown Salt Lake City, take Interstate 15 south to 7200 South (about 10 miles from downtown). Exit and head west for a few blocks, then turn south at the stop light (following the signs to the mine) and then west again on 7800 South. Proceed through the unsightly towns of West Jordan and South Jordan until the road turns into state Route 48 and begins to climb through fields. In about eight miles there is a junction with state Route 111. To visit Copperton, a beautiful historic community hard against the mine, continue straight. To get to the visitors center, head south another four miles. On the right is a large copper-colored sign for the mine. Turn in, pay a $3 per vehicle fee, and drive up the mountain to the visitors center. The center is open from 8 a.m. to 8 p.m. every day from about April 1 to October 31. Entrance fees are donated to local charities.

An alternate way to see the mine is to continue south on state Route 111 through the town of Lark and take a left (west) into Butterfield Canyon. Follow this dirt road (open only in the summer) for about a half-hour to the crest of the Oquirrh Mountains, then take a four-wheel drive road which heads north from the summit. In about 15 minutes the road tops out on West Peak, 9,068 feet, where you can look down at the entire mine complex and even hear its dull roar.

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