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Chile's huge open-pit copper mine goes underground

By Luis Andres Henao

Associated Press

Published: Thursday, Oct. 11 2012 9:50 a.m. MDT

In this Sept. 25, 2012 photo, workers build a steel frame inside a drilled tunnel under the Chuquicamata copper mine in the Atacama desert in northern Chile. Experts say that by 2019 the Chuquicamata copper mine will be unprofitable, so state-owned mining company Codelco is trying to head off closure by converting the open pit into the world's largest underground mine. Codelco believes the mine still has much more to give, with reserves equal to about 60 percent of all the copper exploited in the mine's history still buried deep beneath the crater.

Jorge Saenz, Associated Press

CHUQUICAMATA, Chile — From above, it looks like a colossal amphitheater carved from rock, or the vast crater from a meteorite that crashed into Chile's Atacama desert ages ago.

Inside the world's largest open-pit copper mine, dump trucks as big as two-story houses work around the clock to haul hundreds of tons of rock and minerals 2,790 feet (850 meters) to the surface of this elliptical, seemingly endless, man-made hole.

But the open pit has run its course at Chuquicamata — the storied mine that awoke the political awareness of a young Ernesto "Che" Guevara in the 1950s, inspired Marxist President Salvador Allende to nationalize the copper industry in 1971 and generated decades of prosperity for Chile.

After a century of exploitation, Chuquicamata has become too big, too deep and too old to continue digging in the open-pit method. The giant trucks that carry copper ore each guzzle 819 gallons (3,100 liters) of fuel a day driving 7 miles (11 kilometers) to the surface with ever-poorer loads as ore grade dwindle and copper yields fall.

Chuquicamata produced 443,000 tons of copper last year, but experts say that by 2019 it will be unprofitable.

So state-owned mining company Codelco is trying to head off closure by taking the daring step of converting the open pit into the world's largest underground mine.

Codelco believes the mine still has much more to give, with reserves equal to about 60 percent of all the copper exploited in the mine's history still buried deep beneath the crater. It has started digging more than 620 miles (1,000 kilometers) of tunnels underneath the pit in a $3.8 billion project to revive the mine.

"The technological challenges are enormous. We're talking about changing the biggest open pit copper mine in the world to the biggest underground mine in the world. This type of project is unique," said Juan Carlos Guajardo, head of CESCO, a Santiago-based mining think tank.

Engineers are building four huge floors underneath the pit, in addition to the tunnels, to extract 340,000 tons of copper a year from beneath the ground. The trucks will be replaced by conveyer belts that will carry ore to the grinding machines and the smelter.

Alvaro Aliaga, general manager of Chuquicamata's underground project, said the project will put Chile on "the vanguard of global mining.3/8

All over the world, the race for resources is forcing countries to spend more and drill deeper than they ever have before. Energy companies in the United States are using hydraulic fracturing to tap huge gas and oil reserves from Pennsylvania to Alaska. Argentina is preparing to explode rock to get unconventional oil and gas in Patagonia. Brazil has pioneered deep-water drilling techniques in the Atlantic.

These long-term, multibillion-dollar projects are creating technological feats and opportunities for new industries unseen since the U.S. space race.

"This resembles some of the projects in Argentina and Brazil in terms of its magnitude and the challenge they represent for engineering because they're works of a tremendous scope and with a huge impact on the national economy," said Aliaga.

Work has already begun on the tunnels at the mine, which is 745 miles (1,200 kilometers) north of Santiago in the world's driest desert.

Perforating the rock with a machine that looks like a giant yellow praying mantis, engineers lay explosives that blast through the cavernous walls for ventilation shafts.

"Two of these five tunnels are going to be built to inject clean air and make sure the dirty one comes out," Maria Cristina Vallejos, the only female miner at Chuquicamata, said as she took cover from a nearby blast. "They'll give us the best environmental conditions for the underground work."

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