Mine turns to new technology to preserve operation

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Scott Terry steered the Joy continuous miner 400 feet underground and 600 feet into the highwall at Colowyo Coal Company.

While the continuous miner excavated 500 tons of coal per hour, Terry sat back in a comfortable chair, operating the machine with joysticks and viewing its position on monitors and television screens.

Coal cars carried the wealth of coal out of the tunnel that no miner should ever have to enter. A conveyor belt piled the coal nearby, where it waited to be loaded into a CAT 420-ton hauler to be taken to the train for shipping.

This is Colowyo's final effort to extend the life of the east coal pit. The entire works, including the continuous miner that digs the coal, the cars that haul it out of the tunnel, and the conveyor belt that piles the coal, is known as the highwall miner.

After digging in the east pit for 27 years, the major coal seams had been exhausted and it wasn't economically feasible to continue surface mining there, said Juan Garcia, senior mining engineer. But there were still four good seams of coal that extended 1,400 feet after the pit ended. Just a few years ago, that coal would have been lost.

But new highwall mining technology is enabling coal companies to mine smaller coal seams at the same time they reclaim a site. Garcia estimated the highwall mine could retrieve an additional two to four million tons of coal.

"When you get to the end of a mine's life, you'd never mine surface coal out again, so you'd fill in the pit. Now we come in with this machine and realize coal tonnage that might have been lost," Garcia said.

The 400-vertical foot virgin highwall in the east pit is one mile long. Four black seams can easily be spotted in the highwall. The miners are currently excavating the lowest seam. Every 10 feet along the seam, they launch the Joy continuous miner into the earth to dig a tunnel 11 1/2 feet wide and 6 1/2 feet high that extends an average of 1,100 feet.

Joy is as well known among miners as CAT is among excavators and construction workers. As the continuous miner digs into the wall with a force of 1,300 pounds per square inch, Terry controls the machine safely from his seat inside the control center, observing it from three cameras positioned on the miner and a screen that indicates the machine's pitch, deviation, depth and roll.

Two surveyors continuously monitor the highwall miner's position, checking that it stays perpendicular to the highwall. If the continuous miner were to be even half a degree off course, by the time it reached 1,000 feet into the highwall it would break into a parallel tunnel.

Two gathering arms break the coal from the seam and feed it back along the long flat coal cars that expel it from the tunnel. The highwall miner does all the underground work. No one should ever have to enter the tunnel, Garcia said.

With the speed of the continuous miner, a crew of 10 workers can excavate a 1,100-foot tunnel within one 12-hour work shift.

The 10-foot spaces between the tunnels are called web pillars. After every 20 tunnels, the miners leave a 31.5-foot barrier pillar to stabilize the tunnels, to prevent a domino-like cascade if any of the tunnels were to collapse, and to stop a fire were one to start in a tunnel.

Once the first seam is exhausted, Colowyo workers will backfill the pit with spoil rock until they reach the next seam. Then the process will begin again and new holes will be punched along the length of the high wall. It's an especially effective practice since the company must backfill the pit anyway, Garcia said.

Once the four seams have been exhausted, the company will finish filling the pit, grade the surface to match the lay of the surrounding land, then finish the reclamation process by landscaping the site.

The operation is similar to an auger operation Colowyo attempted in the past, Garcia said. With auger mining, a corkscrew was drilled into a highwall with the same goal as highwall mining. But the practice was ineffective, because the corkscrew only reached 400 feet into the wall and the operators had little control over it.

Kennecott Energy, the owner of Colowyo, contracted Mining Technologies Inc., a Kentucky-based mining company, to start the highwall mining operation. Commonly referred to as MTI, the company is one of only a handful of businesses that offer such mining services, and the only company to perform such an operation West of the Mississippi River. The highwall operation is the first of its kind in Colorado and the third ever done in the West, said Mel Darby, MTI superintendent.

Half the workers on the two 10-member crews are local while the other half are from Kentucky and West Virginia. Garcia said Colowyo is working toward localizing the entire crew, which consists of three column laborers, a bulldozer and a loader operator, an electrician, a mechanic and a foreman. Garcia expects the highwall project to last about two years.

Darby expects highwall projects to soon take off in the West. Such operations are already popular in Kentucky and West Virginia, the country's leaders in coal production.

"As mines mature to the economic limit, companies look to expand the life of their operation," Darby said.

He said he's heard interest from other mines and expects eight or nine such projects to be underway in the West within 10 years.

Rob Gebhart can be reached at 824-7031 or by e-mail at rgebhart@craigdailypress.com.

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