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Taking into consideration the many recent changes intechnology, regulations, design and other factors thathave made their footprint on todays mining operations,

where is the underground coal mining industry headed?By: John E. Feddock, P.E.

Senior Vice PresidentMarshall Miller & Associates, Inc.

During 2010, we at Marshall Miller & Associates, Inc. observed numerous changes in the underground

coal industry, which experienced a difficult year, probably the most difficult if not the most challengingyear to mine safety, since the late 1960s. In business terms, underground coal mining, especially in theCentral Appalachian region of the U.S., is a mature industry in that it operates with experiencedpersonnel, uses well established mining systems, operates the most technologically advancedequipment, and produces steam and metallurgical products that are in high demand both internationallyand nationally. Investment in the U.S. coal industry by foreign companies continues at a fever pitch aswe continue to see a growth rate in the international market. Despite increasing production andconsumption in China, India and other developing countries, U.S. coal mining companies struggle tocompete under an anti-coal administration at the federal level, an ever increasing onslaught ofenvironmental restrictions and regulatory changes, and with changes in mining conditions in coal seamsthat in many instances are unprecedented. These challenges create the need for a more technologicallyadvanced miner and engineer using state of the art measurement systems, computer analysis and minemonitoring, as well as implementing old techniques in innovative ways to safely mine coal underground

today and in the future.

Mining conditions have changed in the last decade and this is especially true in the Central AppalachianBasin. Due to the rich mining heritage in the Kentucky, Virginia and West Virginia coal fields, it is trulyrare to find an unmined coal seam in any area of these states that has not been previously overmined,undermined, or more typically both. This is not just a U.S. problem. While speaking with some Russianminers earlier this year, I observed that my father mined the best coal first, to which they resoundinglyreplied yes, and so did ours. All of this undermining and overmining has brought mining complexitiesand conditions to coal seams that previous miners experienced only on an occasional basis, but are nowregular occurrences rather than the exceptions. These changes fall into three categories: subsidence inseams lying above the previously mined lower seam; pressure concentrations from barrier pillars inoverlying coal seams upon lower coal seams; and methane migration from areas previously mined inlower seams to overlying seams or to strata traps above the previously mined areas in underlying mines.

Subsidence of the surface is a well understood phenomenon occurring above longwall panels or aboveareas where pillar extraction or retreat mining is practiced. However, the impact upon coal seams as wellas upon the roof and floor strata overlying such full extraction areas is less well understood. Due to thefrequency of mining above full extraction areas, prediction of potential roof problems, especially withlateral changes in roof lithology and selecting the types of roof support needed for strata reinforcement, iscritical for profitable mining. Available geophysical tools, such as a sonic velocity can measure changesin the speed of sound in strata that is used to predict rock strength and strata integrity, and the acousticteleviewer that profiles the surface of the borehole, mapping not only the occurrence of fractures, but theirorientation and inclination needed for determining the direction of principle stresses. At the very least

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such measurements are beneficial in critical mine locations for understanding the nature of potentialmining problems and designing appropriate control measures.

Pressure concentrations below barrier pillars in overmined coal seams often cause mining problemsincluding roof falls and pillar failure in underlying underground mines, especially where the depth of themine is more than 500 feet below the surface. Computer analysis and modeling techniques can be usedto not only predict where stress concentrations might occur, but the level of such concentrations. Morefrequent use of these methods is necessary to properly design stable room and pillar systems underneathsuch barrier pillar areas.

During 2010, several methane gas outbursts were investigated in coal seams which were undermined,but where the prior methane gas emission history of the overlying coal seam being mined was consideredlow to almost non-existent. The sources of such trapped methane are difficult to trace and are oftenunknown even with advanced laboratory testing and analysis. Such unpredictable outbursts in miningareas with insufficient ventilation to dilute such concentrations of methane could result in an ignition withserious safety implications, injuries, or fatalities. Ventilation simulation programs successfully predict therobustness of a modeled underground ventilation system to dilute possible rapid methane releases and tomitigate any serious consequences.

Understanding the nature and occurrence of difficult mining conditions, such as those described above,

as well as others, presents some of the challenges facing underground coal mining in mature coal basins.It is necessary for miners to understand these potential problems, and for regulators and safetyinspectors to assist in their prediction and investigation. Through the determination of the undergroundminer to succeed, by his awareness of these potential problems, his cooperative efforts to mitigate anyadverse effects, and his use of improved and innovative measurement techniques and predictive tools,future underground coal mining can return to its previous historical record of decreasing accident rates,achieving zero accidents, and improving safety for all.

John E. Feddock, P.E.Senior Vice PresidentMarshall Miller & Associates, Inc.