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� <br /> E <br /> DEC 11987 <br /> APPENDIX II-13-1 MINED L,-%vi►a <br /> RECLAMATION DIVISION <br /> FACTORS WHICH DETERMINE THE MINE PLAN, <br /> RATE AND PROGRESS OF PRODUCTION. <br /> Production and actual recovery of coal reserves depends upon significant factors <br /> which are largely beyond the control of the operator. These include (1) Geologic <br /> Factors; and (2) Market Factors. <br /> 1 . Geologic Factors. <br /> The extreme depth of cover above the mining operations at Coal Basin is a <br /> significant determinant of the rate and ratio of production, and requires constant <br /> adaptation of the mine plan in response to the actual geologic conditions <br /> encountered as mining progresses. <br /> Mining methods, design of the mines, productivity and rate of progress are <br /> substantially determined by geologic factors, and these factors are dynamic and <br /> difficult to predict. At the same time, these factors must be dealt with as they occur. <br /> Intense faulting, dikes and igneous intrusions characterize the geology of Coal <br /> Basin and, because they are found in both of the coal seams being mined, prove <br /> highly disruptive to the progression of mining. Roof control problems, stress zones, <br /> and accompanying change in the pitch of the coal bed are commonly associated <br /> with such zones. Mine plans, on occasion, must be changed to accomodate such <br /> occurences. <br /> For example: <br /> — Longwall 102 encountered an igneous dike in <br /> September of 1985. The dike crossed the face <br /> diagonally from east-southeast to west-northwest, <br /> and averaged 2 to 4 feet in thickness. <br /> — Two dikes 8 -9 and 4 -6 feet thick were <br /> encountered near the lower end of the Longwall 103 <br /> startline entries in later 1985. The thicker dike <br /> crossed the longwall panel itself, and had to be cut <br /> during the first several weeks of operation. These <br /> 1 <br />