Pit & Quarry, February 2010
making stone The mines are similar only separated by about one mile but the stone cuts out between them Overburden varies from 70 ft to 200 ft at both locations Before devising a mine plan to go underground East Fairfield Coal representatives visited a number of other underground mines including salt mines and limestone mines There has to be enough high cover reserves to justify the investment in the mine development and the equipment purchases Mackall said of going underground The thickness of stone is also a big consideration There are also geologic conditions to consider mainly in the composition of the seams above and below the limestone Mine development The Petersburg reserve had a combination of low cover and high cover limestone Mackall explained East Fairfield Coal stripped the low cover reserves to the highwall and went underground in the highwall The Subtropolis reserve is all high cover stone so the company excavated a box cut to reach the stone Most of the Subtropolis mine development was done during the winter when the Petersburg mine was slow Extra employees were available to support the process but Ohio winters made the work difficult and it took several years to complete Asked to describe the biggest daily challenges to mining underground Mackall said The biggest challenges are almost always personnel We try to be as efficient as possible which means when a couple guys are on vacation it can hurt our production Over the years we have tried to cross train our workforce so guys can jump around to different equipment to fill in when someone is out We are fortunate to have a very strong workforce that lets us do that East Fairfield Coal wasnt the first Ohio company to mine stone underground nor is it currently the states sole operator of an underground stone We wash the stone so we have to shut the plant down at around 28 degrees or it will freeze out Jeremy Mackall Vice President East Fairfield Coal Co mine Mackall said However the company does field questions and requests for tours from operators wanting to see its production process and learn about various problems Equipment utilization Mackall cant pinpoint one piece of equipment that is integral to the operations If one machine breaks the entire process is affected So to avoid interruption in production the company owns spare equipment such as Oldenburg Cannon double boom jumbo drills and Gradall scalers and operates duplicate models of equipment at each underground mine The production of our mine is determined by how many faces we can www pitandquarry com February 2010 PIT QUARRY 33
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