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No matter how many times you visit the Kennecott Utah Copper open-pit mining operation in western Salt Lake County you never get over the enormity of the operation.

Everything at the mine for many years has been on a large scale, and now that the $400 million modernization project is complete and operating smoothly, the bigness is even bigger. Consider for example:- In the mine, 5 billion tons of material - essentially an entire mountain - have been removed in the past 80 years, leaving a gaping hole in the Earth that is 21/2 miles wide across the top and more than one-half mile deep.

- Electric shovels loading the diesel trucks have a capacity of 27 to 30 cubic yards or 50 to 60 tons.

- The trucks hauling the material to the crusher have capacities of 170 to 200 tons and have tires 10 feet tall.

- The $400 million modernzation project itself was a significant amount of money pumped into the economy, much of it going to Utah companies and workers.

- Even the 2,100 Kennecott workers benefit in a big way from the mining operation. At the ribbon cutting ceremony Friday, G. Frank Joklik, president and chief executive officer of BP Minerals America, parent company of KUC, announced that 2,100 workers each will receive a $2,000 bonus, a total of about $4 million. For the union workers it is in addition to the $1,000 they received in 1986 and again in 1987.

In fact, the entire process is so amazing that it bears repeating.

A 60-inch by 109-inch Allis Chalmers gyratory crusher reduces the ore to pieces no larger that 10 inches.

After the material is crushed in the gyratory crusher it falls onto a 72-inch conveyor belt that runs through an old 3.2-mile railroad tunnel and two miles farther north of the mine. The conveyor moves material at 900 feet per minute and has a capacity of 10,000 tons per hour. This replaces the inefficient railroad system that hauled the material to the concentrator in Magna.

At the end of a 281/2-minute trip on the conveyor belt, the copper-bearing ore falls into a covered A-frame stockpile area that can hold 350,000 tons, a seven-day supply. From there it is taken from the bottom of the stockpile on three conveyors into the new concentrator building.

Once inside the concentrator building, ore is ground to quarter-inch size in three grinding mills 34 feet in diameter (the largest in the world) each driven by two 6,000-horsepower electric motors. Ore less than a quarter-inch in diameter is sent to six 18-foot diameter ball mills and ground to the consistency of face powder.

The finely ground ore moves to the flotation cells where the metal is separated from the waste rock. The metal-bearing particles are drawn off the surface of the 3,000 cubic-foot flotation cells (the largest in the world) and form the concentrate that is 28 percent copper.

The concentrate is pumped nearly 17 miles to the smelter in a 6-inch pipe and the waste material flows to the tailings pond in a 48-inch concrete pipe 13 miles away.

Annual production at the Kennecott operation is 200,000 tons of refined copper, 300,000 ounces of gold, 2.3 million ounces of silver and 12 million pounds of molybdenite.