Giant open-pit Chilean copper mine moves underground

Chilean miners at one of the world’s biggest open-pit mines will soon be digging for copper underground, in a move to extend the life of the century-old site for 40 years. The Chuquicamata mine and six other pits owned by state company Codelco together provide 11 percent of world copper output – some 1.7 million tonnes a year, according to the firm. However the gargantuan Chuquicamata pit – five kilometers (three miles) long, three kilometers wide, and one kilometer deep – is reaching the point where it is no longer cost-effective to operate using current extraction methods. The solution? Go underground. “This will not be just any underground mine,” said Roberto Pasten, who manages Codelco’s Chuquicamata division. “We’re talking about this becoming one of the world’s two or three largest underground mines, so this isn’t an easy project,” Pasten said. The Chuquicamata mine produces some 300,000 tonnes of copper a year. Chile is the world’s biggest copper-producing country, accounting for 28 percent of global production, according to the Chilean Copper Commission. Chuquicamata is located in far northern Chile some 2,870 meters (9,400 feet) above sea level in one of the driest places on the planet. Known to locals simply as Chuqui, the mine employs nearly 6,000 people. The site is so vast that three-story-high Komatsu dump trucks, equipped with tires the size of two adults and capable of carrying a 330-tonne load, are swallowed into the hole as they zig-zag down 10 kilometers of road towards the pit floor. Dinosaur-sized mechanical shovels at the bottom claw into the ground with scoops large enough to hold a crew of workers, and dump piles of rock into the truck’s hopper. On each round trip, the giant 18-cylinder dump trucks guzzle the equivalent in fuel of what an average car uses in 21 months. “It’s becoming too expensive to transport each ton of minerals given how deep the pit is,” said Pasten. Although the mining operations will shift underground, the system and vehicles for extracting the copper are forecast to be less costly. “If we do not carry out these changes … definitely our level of production will collapse, and Codelco’s position in the world copper market will decline,” Pasten told AFP. After a decade on the drawing board, digging for the underground phase began in 2012 under former president Sebastian Pinera. Currently there are nine kilometers of tunnels linked mainly to the mine’s ventilation system, and another 7.5 kilometers for vehicles. Some 1,000 kilometers of galleries and tunnels are planned, equal to the distance between Paris and Berlin. About a quarter of the project has been completed, and when it is finished in 2019, it should extend Chuquicamata’s productive life for four more decades. In the meantime, both open-pit and underground operations will work at once, with the goal of producing 340,000 tonnes of copper a year. The old mine will be slowly abandoned, although a small section will remain as a historic site to remind Chileans what the mine represented for their country’s economic development. In 2007, Codelco closed down a camp near the mine where thousands of workers and their families lived. They were moved to the nearby town of Calama, population 150,000.