ILL DIGGING BRYA N S C H U T M A AT
he entrance to America’s deepest mine shaft sits on a plateau high above the Arizona desert, about an hour east of Phoenix. Tucked against the base of a ridge of steep cliffs, it looks southeast over miles of ragged boulder fields. What looks like a large capital A rises above its entrance. It’s the steel headframe used to hoist equipment in and out of the shaft, a concrete tube 30 feet wide that goes 6,943 feet straight down.
The No. 10 mine shaft, as it’s called, is on the southern edge of an old underground mine. For 86 years, the Magma Superior mine pulled copper and silver out of the surrounding mountains before closing in 1996 when the minerals ran out. Over its lifetime, Magma grew to include nine separate shafts, some of them miles apart. The final shaft, No. 9, was finished in the 1970s. After Magma closed, No. 9 sat abandoned for nearly 20 years before becoming part of the new Resolution Copper mine. It’s now the ventilation shaft for its younger, deeper cousin, No. 10, just a few hundred feet away.
Visited on a chilly day in December, the area around the top of the mine, the “collar” in mining terms, doesn’t look inviting. Steam clouds pour from the mouth of No. 9. It’s the hot air being drawn from the cave dug at the bottom of No. 10. That far down, rocks formed billions of years ago still carry heat from the molten core of the earth. Without the elaborate refrigeration system that pumps chilled air down No. 10, the bottom of the mine would be 180F, far too hot for a human to withstand. “You’d cook,” says Randy Seppala, 60, project manager for shaft development. Miners have long called this heat the “hand of the devil,” reaching up from the depths. Seppala works for Resolution Copper Mining, a venture between the two largest mining companies in the world, Rio Tinto and BHP Billiton. Together they’ve spent more than $1 billion, including $350 million sinking the No. 10 mine shaft, in hopes of tapping nearly 2 billion metric tons of ore. Less than 2 percent of it is believed to be copper. It might not sound like much, but that’s considered dense, making it the fourth-largest undeveloped copper deposit in the world.
Resolution Copper plans to dig four more shafts over the next 15 years. At peak production, this will be the biggest copper mine in the U. S., producing 100,000 tons of rock a day, and enough copper to meet a quarter of the country’s demand. It could also end up being a financial problem for its owners. The price of copper, along with lots of other commodities, has crashed as China’s economy has slowed. The Resolution mine is essentially an enormous bet that the thirdmost-used metal in the world is oversold and that prices will rebound by the time the mine opens in several years. “This is a pretty big gamble,” says Dane Davis, a commodity analyst at Barclays. “We’re in a new era for copper, and no one truly knows what demand is going to be like. So I would say this is quite risky.”
Before going down the No. 10 shaft, visitors learn how to put on an emergency breathing kit consisting of a nose clip, breathing tube, and small oxygen bag you attach to your belt. As the safety video points out, a fire or explosion can occur at any time in an underground mine. Your ability to survive depends on being prepared.
There are lots of ways to die in a mine. Roughly in order of likelihood, the most common include getting struck by objects falling down the shaft, falling down the shaft yourself, and being killed by an explosion. In the last case, it’s probably not the fire that kills you, or even the force of the blast. It’s the toxic gases that get released, particularly the high concentrations of carbon monoxide. According to Andy Bravence, Resolution’s mine superintendent and Seppala’s No. 2, the breathing kit can get used up in a few breaths if you’re hyperventilating. Dangerous levels of carbon monoxide are in the range of 3,500 parts per million. “One breath of that, and pretty much she’s gonna collect your insurance,” Bravence says. “It sucks all the oxygen out of the blood and knocks you out. Your next breath you won’t remember taking, and you’re pretty much done after that. But you know: Don’t worry.”
Bravence, 56, is wider and taller than Seppala, who’s lithe and lean. Both men have impressive mustaches and walk around most days in either jeans and steel-toed boots or navy blue canvas overalls called diggers, which have built-in boots. As we prep to go underground, they’re both in their diggers, Seppala with a camouflage baseball cap pulled low over his eyes, Bravence in his mining helmet. Seppala spends most of his time these days above ground, but Bravence goes down almost daily to check on the work.
One descends No. 10 in a giant bucket or in a metal cage. Both travel at 500 feet per minute, or a little faster than 5 miles an hour. Yellow decals in the cage warn of hazards using pictures of stick people in various states of danger: One has an arm caught between gears; another is getting hit by falling rocks. The concrete shaft runs by, almost close enough to touch through a few half-dollar-size holes.
“What happens if we turn off our helmet lights?” I ask.
“You find the true definition of dark,” Seppala says. We turn them off. Blackness, and the rumbling cage.
After eight minutes a low roar from below picks up. By now, about 4,600 feet from the surface, and 400 feet below sea level, the air pumped down by the refrigeration system has lost its chill. At this depth, Resolution has built a second cooling station, dug laterally off the mine shaft. Here, the air gets circulated through a second set of giant cooling coils, built into the rock and encased in metal. Two fans, 5 feet wide, blow the freshly chilled air back to the bottom of the mine. A giant duct carries it the remaining 2,300 feet down.
Back in the cage, it takes an additional seven minutes to get all the way to the bottom of the mine. Seppala steps out and immediately wipes fog off his custom-made safety glasses. Steaming hot water pours off the rocks; during construction, workers bored into an ancient lake trapped thousands of feet underground by impermeable rock, and it’s leaking into the mine. It’s like standing in a tropical rainstorm. A digital hydrometer on the wall registers 100 percent humidity. Overhead, cooled
air gushes out of a metal duct, blowing the rain sideways and keeping the temperature in the mid-70s.
In a few years, this tunnel will have offices and high- speed Internet where engineers and geologists can work without having to go back up to the surface. Right now it’s a hot, wet cave: Steam billows past floodlights hung from the ceiling; pipes and cables, some of them jiggling, run along wet, rocky walls; a frontend loader stays dry under a party tent bought at Walmart.
Seppala walks warily around in the rain, a spotlight on his yellow hard hat pointing the way. At the bottom of the mine, a 170-foot lateral tunnel is laid out like a cross. On the left is the pumping station. A 6-foottall submersible pump in 20 feet of water beneath the shaft fills a dumpster-size tank. From the tank, two large pumps each shoot 700 gallons a minute up to the surface, where it’s treated and used by local farmers. If the whole thing stopped working, the tunnel would flood in 15 hours. Two life preservers hang nearby, just in case.
Across from the pump station, a thick vein of cables delivers 4,100 volts of power into a metal shed. Perfectly dry, bright, and clean inside, it’s filled with racks of humming electrical gear, transformers, and switches. The shed runs everything from the lights to the pumps to the drills to the immaculate, industrial-use portable toilet. A two-man drill crew works at the head of the tunnel, boring test holes into the rock. They look like Spider-men: Wire mesh covers the lenses of their safety glasses in a protective black screen. Seppala motions off to the side of the tunnel, his arm cocked at a 45-degree angle. “It’s up that way,” he says, meaning the copper deposit, still behind several hundred feet of rock. “That’s the whole reason we’re down here.”
Southeastern Arizona has been mined for more than a century, but it wasn’t until the 1990s that geologists found the massive deposit next to No. 10. For decades they speculated about something bigger lurking beneath the shallower veins of copper running under the desert. Whatever was down there was deep though, more than a mile down, and far outside the reach of cost-effective mining techniques. Then, in 1994, as the Magma mine was running out of copper, a team of geologists bored a test hole under the Tonto National Forest and hit pay dirt. Deposits this big are usually strip-mined, but this one is too deep, so Rio Tinto will mine it from the bottom up. As it’s drilled and blasted from below, the ore will crumble and drop into a series of chutes and conveyors. This type of mining, called block caving, has been around since the 1950s, but it’s never been done at anywhere close to this depth or on this large a deposit.