Untitled Document
 

Gold Mining in Alaska
Atlas Copco Equipment Used for Underground Development
By Scott Ellenbecker

One hundred twenty years ago, gold was discovered at
Comet Beach, 45 miles up the coast from Juneau, Alaska.
From this beach, a mountain rises gradually at first, then
steeply to a peak about two miles inland at just over 3,000 ft
above sea level.

Gold seekers panned their way upstream, and then began
underground tunneling nearly two-thirds up the mountain.
Those early miners had no idea what they were standing on.
Modern exploration has identified the major find known today
as the Kensington vein. It's roughly 400 ft wide, 1,200 to 1,500 ft
long and extends from the mountain top to 120 ft below sea level.

Mining on the opposite side of the mountain from the original
mine workings, Kensington's mine camp looks up to
the mountain peak called the Lions Head. The gold runs into
the depths of that mountain.

Coeur Alaska, which took 100 percent ownership of the property in 1995, began mining at Kensington in July 2010. In the first two months, the mine transitioned from a development crew of nine to a production crew of 50. Today 180 miners and another 20 consisting of camp support construction workers and contractors are in camp. It took just eight months to get the operation to full speed, producing 1,200 to 1,300 tons of ore per day.

Second Chances

Coeur actually started mining at Kensington twice. From a September 2008 startup, mining operations continued to June 2009. The ensuing permit battle went all the way to the U.S. Supreme Court, which ultimately ruled in favor of Coeur.

The brand of drilling equipment Coeur purchased for use in the mine's first operation were sent to another Coeur property. When operations started again, management looked closer at other suppliers. The technology and support from Atlas Copco and its Alaska distributor, Construction Machinery Industrial (CMI), tipped the scales.

Mine superintendent Ezekiel Easley has been at Kensington since the beginning. "We've come a long way in a short time."

The mine operates four Atlas Copco drills, a Simba M7C long-hole production drill, two Boltec MC bolters and two Boomer M2C face drills.

Mine maintenance planner Naomi Hammond is responsible for coordinating parts and communicating with vendors like CMI. "They have been a real life saver at times," she said. Maintenance general foreman John Hecker agreed, commenting on the very limited space to warehouse parts - even critical parts. "Although we have substantial resources, we are lacking real estate and really count on CMI," he said.

The mine's goal is to have three maintenance technicians on each of the three shifts.

Scheduling is important because they have only one bay, but the drills have not been a problem. "The drills have a 93 percent availability overall while the Boltec is 90 percent," said Hammond.

One of those maintenance techs is Shawn Duval. He said the only real problems to date have been related to human error. "There are fail-safes built into the rigs that make it hard to wreck anything. The computer doesn't let the rig drill over its boundaries. In the old days, drillers would push them till they would come apart or blow a hose. You can't do that with these."

He said it's also gotten easier to be a mechanic with the technology on these new rigs. "It can be intimidating - for drillers and mechanics - but you just have to trust what the computer is telling you. If there is a problem, nine out of 10 times it requires something as easy as cleaning a magnetic pickup."

Duval said, "These things are made to have rocks drop on them and be wet all day. Most damage comes from tramming or operator error. Problems are usually self-inflicted."

For the mechanics, fixing a drill includes drilling a hole. "The machine tells you what the problem is, which makes it easy to work on and operate. Like I said, you just have to trust what the rig is telling you. And they run so smooth, once a guy operates this rig, he won't want to go to anything else."

He said, "You're not forcing things on these drills. Drilling requires a different mental attitude and a little finesse. With the older drills, if you're running three levers you really feel like you're getting a lot done. With these rigs, it's about working efficiently and not rushing it. You will get more done if you just trust the rig and move at its pace."

"Before computers, a driller had to feel it, hear it, hold the hole. A driller can't be as accurate as a computer, not after a full day, on every hole," said Duval, speaking about Tunnel Manager, Atlas Copco's Rig Control System. The computer program on the rig integrates with the mine's survey program. For software, the mine uses Vulcan, but Easley said Gemcon does the same thing.

Accuracy is important at Kensington. "We have to make sure our holes are put where they are supposed to be," said Easley. "Eighty percent of the mining at Kensington is long-hole stoping - but it's more involved, there's more to it."

The mine advances 40 ft per day in four rounds. There are four or five working headings in five different areas. Mining follows the ore body. "We are not getting any dilution. Before shooting, everything is surveyed - collar to bottom. We use cameras to grade everything."

He pointed out that other mines may focus on tons, but their goal is to be accurate and keep dilution to a minimum.

"It's important to be accurate and we watch it close. Once the ore rolled over on us and the east hanging wall went to a west hanging wall within the same longitudinal stope," said Easley.

Mining is done with a slash-cut drift 15 ft x 15 ft in 45-ft lengths. An upper and lower drift are cut. The Simba drills lateral holes angling at varying degrees that fan out from the upper stope down 60 to 110 feet.

The Equalizer

When drilling the angled holes, Tunnel Manager makes a big difference for accuracy. Easley said, "Top quality long-hole drillers are hard to find. The most experienced long-hole driller at Kensington, Jeff Corner, has been drilling most of his career. His skill as a driller ranks with the best," said Easley.

Tunnel Manager makes mid-level miners top quality miners in weeks. "Jeff can place the bit exactly where he needs it, but that skill is developed over time. The computer does it for the driller. He just needs to watch the computer screen. The computer also gives him all the parameters and drilling data. Over time the computer's consistency makes everyone faster and more accurate."

When looking for equipment to develop the mine, the technology
and support from Atlas Copco and its Alaska distributor,
Construction Machinery Industrial (CMI), tipped the scales.

Not that the computer will replace a quality driller. A driller's skill
helps set up faster, and if something on the wall makes it so the
hole cannot be drilled at the computer's selected location, the
good driller can adjust without the computer giving him the angle.

Easley said, "An experienced driller can drill 1,000 ft a shift, but
with Tunnel Manager a mid-level miner can be drilling 1,000 ft after
the first month, and in two months he's drilling like an expert."
 
Even for expert miners, Tunnel Manager makes the job easier.
"Ninety degree holes are where this thing really shines," said
Kensington trainer Justin Wilbur. Wilbur also conducts
performance evaluations and establishes checklists to ensure
miners follow a routine. "We want everybody doing everything
the same so each person is doing it the same. Tunnel Manager
equalizes everybody, even the experienced guys like it."

Faster Bolting

Easley said bolt-hole drilling goes smoother too. With the Atlas Copco Boltec, a driller can get 20 to 30 more bolts in a shift. "Setup is faster because you can look ahead to what's next rather than watching the current installation."

The Boltec also installs both friction bolts and Swellex bolts. The mine uses 8-ft Super Swellex. "Operationally it's nice because it's easy to switch bolt types without having to go to a different machine," said Easley.

As for the rock drill used on the Boltec, the mine has operated both the 1132 rock drill and the 1532 rock drill. Easley said the 1132 is slower because it's lighter, but it causes less stress and maintenance on the machine. A miner can install 150 bolts per shift when drilling a 1 3/8-in. hole, and that goes down to 100 to 120 with the 2-in. needed for the Super Swellex. They usually don't have to screen in ore.

Efficient Face Drilling

The Boomers use the 1838ME rock drill. In the beginning it would take an hour and a half to drill the 15-ft face. That equals 65 to 70, 12-ft deep, 1 ¾-in. holes. A round would take 2 hours, including hook-up and scaling. Now they have changed the pattern and are drilling 90 holes in two hours.

When the miners purchased the Boomers, they decided to go with two computer screens rather than one. The intention was to have one for a trainer. Now the drillers are using a screen for each boom. The driller will set up and start one boom drilling and move to the next, going back and forth until the pattern is drilled out. "Although this can be done with one screen, you can see the operation while the other is working and it gives the driller time to visualize and think ahead," said Easley.

The operation is as simple as putting the bit face to match the spot on the computer screen and adjusting to the angle shown on the screen. Once in place, the driller pushes a button and the computer takes over until the hole is drilled, automatically flushed and the rock drill retracted. The mine uses Secoroc R38 x HEX35 x R32 for the 14-foot steel.

Although the mine went through many legal hoops before it became operational, Mine Manager Henderson said it's a great operation now and has become an excellent asset to the community. The permitting included a commitment to employ 25 percent of the workforce locally, which has been made easier because of the automation of the drills.

As in almost any mine, crews fly in from all over, but many employees have moved to the area and become part of the community. Henderson said, "Kensington is a real family-oriented mine with families interacting in the community and participating in community activities. It makes for happy miners if their families are close." Although many of the miners stay in camp, many others take the ferry and mine-bus back to town at night.

They also employ many subcontractors from the local population to work in support organizations, such as security, catering and transportation services.

The mine has known reserves of 1.6 million ounces of gold and 5.5 million tons of ore. Henderson said with current and known reserves, "that puts the mine's life out 20, 30 years, or beyond."

Mining has been a big part of the local history for a long time, and Kensington will continue that tradition for years to come.


Scott Ellenbecker is Editor-in-Chief of multiple in-house publications for Atlas Copco, and the president of Ellenbecker Communications, an international communications firm specializing in the drilling, mining, and construction industries.

Source: http://www.tunnelingonline.com/featurestory/featurestory5.php

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Computer aided drilling helps ensure accuracy and productivity.

When looking for equipment to develop the mine, the technology and support from Atlas Copco and its Alaska distributor, Construction Machinery Industrial (CMI) , tipped the scales.