The machines that mine Alaska
One of nineteen Caterpillar 793D trucks in the Fort Knox fleet. This one’s new and cost $4.2 million; it can haul a 240 ton load.
Photo by Greg Martin for Kinross Fort Knox.
Elephants likely aren’t the first thing that comes to mind when talking about mining in Interior Alaska, but they are an apt metaphor for the equipment used at Fort Knox gold mine.
Fort Knox, owned by Canadian mining firm Kinross Gold Corporation, is located about twenty-five miles northeast of Fairbanks. The mine is dominated by an enormous pit that is more than 1,400 feet deep and a half-mile across. The pit resembles a gigantic inverted ziggurat, with thirty-foot benches ringing the sides. From the top, what looks like a line of Matchbox-size trucks rumble down the road to the active mining area where they are filled with ore before heading back up the pit to the crusher or heap leach.
Only when they come near does the scale of the whole operation become apparent. This is where the elephants come in.
“We ask the school kids ‘How many male African elephants do you think can fit into this 240 ton haul truck?’” says Anna Atchison, manager of community and government relations for Fort Knox. The question is an icebreaker on schoolkids’ tours of the mine, but it’s also a pretty good indication of the size of the trucks. The answer is thirty-five.
The huge trucks are necessary for the scale of operations at Fort Knox, where more than 5 million ounces of gold have been produced since 1996. The gold itself is microscopic. In the more than one hundred years of mining in Interior Alaska, the nature of the ore bodies, as well and the methods and mining equipment, are constantly changing, refined, and updated.
The Bucyrus Erie 1300 W walking dragline is affectionately named “Ace in the Hole.” The dragline is capable of moving 33 cubic yards per bucket-load of overburden every minute.
Photo courtesy of Usibelli Coal Mine
Big Change in Equipment
When prospectors first moved through Interior Alaska in search of gold in the late 1800s, they carried the standard mining equipment of the day: a pick, shovel, and gold pan.
Onsite, they constructed sluicebox and rocker boxes to separate the gold from the paydirt. But Interior Alaska’s goldfields were far different from those of the Klondike, where gold was found relatively close to the surface. Alaska’s precious metal was often buried under twenty feet of frozen silt and muck.
Wood fires and later steam points were used to thaw the ground. Pressurized hoses were aimed at the hills to wash away the overburden. Later, huge dredges were brought in to sift every possible ounce of gold from the valleys.
Today, most small to mid-size placer miners use Caterpillar D8 or D9 bulldozers to move earth, says Marty Williams, who has been a product support representative for thirty years at N C Machinery in Fairbanks.
Even those have changed over the years, he says.
“Like automobiles, they’re more environmentally friendly, more green,” says Williams. “They’re much more complex. Most of them are equipped with computers.” Even the oils and lubrication agents are improved. He sees a lot of that change how the equipment runs in the winters, which often see temperatures of forty to sixty degrees below zero in Interior Alaska.
“In the early ‘70s, our cars wouldn’t run very well when it got to forty below,” Williams says. That’s rarely a problem today, he notes.
A view of the trucks at the Fort Knox mining site from the top of the pit helps show the scale of the mine.
© Julie Stricker
Ace in the Hole
At Usibelli Coal Mine in Healy, summer maintenance can often be more difficult than for winter, says Bill Brophy, vice president of customer relations at Usibelli.
“In the summer months, you have warmer temperatures, so engines and transmissions run at higher temperatures,” he says. The temperature of the tires is a major factor in performance and safety, Brophy notes. The condition of the roads is also a factor.
In the summer months, roads can frequently get rutted or get a washboard effect, whereas in the winter months, the roads are essentially frozen and more stable. “Once they’re graded with a road grader, they’re just like a paved highway,” Brophy says. “They’re more comfortable for an operator and they’re more comfortable to travel.”
Brophy likes to quote mine founder Joe Usibelli about the challenges of mining coal: “Mining coal is easy. Getting to it is the hard part.”
The coal seams are layered under many feet of dirt and rock. Brophy says there are four basic ways of moving the overburden:
• A bulldozer, which is used to push material short distances
• A shovel and a daisy chain of trucks, which are choreographed so that a truck is always ready for the load from the shovel, but neither is kept waiting
• A drill rig and explosives, which are used to cast blast the material away from the seam
• A dragline, which is Usibelli’s hallmark piece of equipment, affectionately nicknamed the “Ace in the Hole” by Healy schoolchildren
The Ace in the Hole is a 1300W Bucyrus-Erie walking dragline that Usibelli purchased in 1977. It took twenty-six railcars and forty trucks to deliver the components of the machine to the mine site, where it took eleven months to assemble. It is the largest land-mobile machine in Alaska.
Two operators are on duty at all times, one to operate the bucket and the other to perform needed maintenance or other duties. The dragline itself is powered by electricity. The bucket of the dragline holds thirty-three cubic yards of material and is used to remove overburden, not the coal.
The addition of the walking dragline allowed Usibelli to ramp up production in the 1980s and is an integral part of today’s operations, Brophy says. He notes that when the mine went into production in 1943, it was able to deliver 10,000 tons of coal to Ladd Field in Fairbanks over the course of a year. Today, because of the new technology, it can produce 10,000 tons in one day and more than 2 million tons per year.
Among its fleet of equipment are about nine bulldozers, fourteen loaders of different variations, three road graders, three drillers, and eight Caterpillar 785 trucks and three Caterpillar 777 trucks, which have a hauling capacity of 150 and 100 tons, respectively.
A giant Hitachi is used to load another one of the nineteen Caterpillar 793D trucks, Fort Knox’s biggest.
Photo by Greg Martin for Kinross Fort Knox
Large Fleet for Large Mine
At Fort Knox, the fleet is much larger, but so is the mine. The largest piece of equipment is the Hitachi 5600 shovel, the cab of which is thirty-five to forty feet above the ground, says Derek Lakey, who is mobile maintenance senior planner at the mine. It is used in the pit to move the ore.
A fleet of trucks the size of two-story buildings moves the ore to the crusher or heap leach, depending on the grade of ore. The largest are Caterpillar 793s, capable of hauling a 240 ton load. Fort Knox has nineteen of those, the newest of which cost $4.2 million, Atchison says. They are supported by a fleet of nine Caterpillar 789 trucks that can haul 190 tons and ten Caterpillar 785s that hold 150 tons apiece.
“I’ve always equated them as driving like a great big boat, only taller,” Lakey says. “They’re really smooth, really comfortable to drive.”
All of the trucks are equipped with GPS and are monitored through a dispatch system that tells operators where the truck is going, where they came from, what they’re hauling, and what their speed is, Lakey says. A separate system is used for maintenance.
“You can see in real time how much fuel they have, what their load is as far as weight,” he says. “We see problems way before it ever becomes a real issue. There’s just no other way to keep track of everything.”
It’s all about efficiency, Lakey adds.
“It organizes and optimizes your fleet so you have the right amount of trucks at each shovel so you don’t have your shovel hanging and you don’t have your trucks waiting.”
Drivers get eighty hours of training, some in classes, some with a custom-programmed simulator, and some on-site with a trainer, says Craig Natrop, Fort Knox mine superintendent. The simulator is also a way for drivers to test their responses to hazard scenarios such as losing steering. Mainly, Natrop says, it’s a way to make sure drivers are using the machines properly and not inducing unnecessary maintenance.
Fort Knox uses two other unusual pieces of equipment: a D11 Caterpillar dozer and its gyratory crusher. The D11 is about twice the size of a normal bulldozer and is used on the heap-leach to break up the surface so the chemicals can leach through, Natrop says.
The crusher, which was built in 1952, is the largest and oldest crusher in the country. It is used to break up the ore before it is sent to the mill and can handle about three thousand tons of ore an hour.
Although the equipment it uses is enormous, Lakey said it helps Fort Knox keep its footprint much smaller than older mining methods would have.
The maintenance and training operations are pivotal in maintaining a strong safety record, Natrop says.
“That’s really what modern mining is all about,” Natrop says. “We’re safer. We’re more efficient and we’re able to produce more. Those are some of the things we talk about the most, to make sure your people and the environment come first.”
Julie Stricker is a writer living near Fairbanks.
Posted: September 1, 2013