Air Quality Goes Underground

Cool fresh air comes at a significant expense in an underground mine. Air pollution in a hardrock mine comes from a variety of sources — just as it does above ground — but emissions from diesel engines are near the top of the list of concerns. Mine engineers must consider diesel emission levels and ventilation routes, the latter driven by large fans that push and pull fresh air through the mine.

With the prices of raw material at record highs, the mining industry is going strong. After years of keeping older machinery on the job, mining companies are buying new machines in record numbers. Up until very recently the trend was toward boarding up mines and laying off workers; today large firms are desperately seeking the personnel required to operate the new machinery.

There has been a movement to go back underground in search of paydirt. A century ago, miners in boom towns in Arizona or Colorado tunnelled after veins of precious metal; it was safer than an open pit and the equipment was better suited for working the narrow shafts. The advent of larger shovels and trucks made surface mining economically feasible. In North America open pit mining clearly leads the mining industry today, but community and regulatory pressures are making deep mines attractive.

"The future for many open pit mines is to go underground," says Chris Gehner, regional manager, North and South America, Caterpillar Underground Mining Pty. Ltd. "Many ore bodies go very deep underground, and making the pit even deeper than it already is not practical."

Gold or coal usually comes to mind first when underground mining is discussed, but the trend to tunnel into the Earth in search of valuable raw material includes stone and aggregates suppliers, as well. Sometimes it's simply a matter of economics, other times environmental pressures make it the only option. By going underground, companies are able to better manage dust and noise; quarries located just outside urban areas can operate 24 hours a day.

Recently, in suburban Chicago, Fox River Stone, South Elgin, IL, became one of the only firms in the country to employ a Voest-Alpine Tunnel Miner ATM 105 roadheader, which it is using to open a 17.5% decline to a huge reserve of dolomite. The firm has extracted more than 50 million tons of it from a surface mine, and it estimates that stock will be depleted by 2007. Most of Fox River's dolomite goes into ready-mix and asphalt plants. More than 300 feet of shale covers the next layer of dolomite. Fox River determined going underground made the most economical sense.

"We've been seeing a trend over the last two years to go underground," says Chris Curfman, president, Caterpillar Global Mining, Peoria, IL. "It takes about half the time to get a permit for an underground mine, whether coal or hardrock, than it is to open a pit. We are also seeing a pent-up demand in North America for underground quarry operations. A lot of people running large quarries are starting to buy our underground trucks. We're talking about the big aggregate companies like Lafarge, Martin Marietta and Pioneer."

Underground mining equipment represents a relatively small portion of Caterpillar's worldwide business. Going forward, Caterpillar plans to give underground mining a significant amount of attention. "We plan to take a commanding position in that industry in the next three years," says Curfman. "Look for expanded product lines and more activity in emerging markets such as Russia, Indonesia, and China."

One step in that direction came earlier this year with the introduction of the R1300G Series II load-haul-dump (LHD), equipped with Caterpillar's C6.6 ACERT diesel. A specialized machine for work underground, the R1300G is less than 85 in. tall and weighs 46,021 lbs. empty (it is equivalent to a Caterpillar 966H wheel loader). The ACERT engine puts out 182 hp to help move a payload of nearly 15,000 lbs at up to 19 mph in fourth gear.