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A'est Elk Mine <br />• Exhibit 60 has been retained in the permit. The discussions in this section, however, focus on <br />the South of Divide mining area, as the primary future mining area, but retain discussion of <br />subsidence parameters for the Apache Rocks, Box Canyon, and West Flatiron mining areas. <br />MCC has made a major commitment to thoroughly understanding and describing the nature of <br />subsidence that will occur in the South of Divide and other active mining azeas. Specifically, MCC <br />has retained Wright Water Engineers, Inc. (WWE) of Denver to evaluate subsidence and probable <br />hydrologic consequences. WWE worked closely with Mr. C. 1Zichazd Dunrud on this project. Mr. <br />Dunrud was employed by the U.S. Geological Survey (USGS) throughout his cazeer and is a <br />recognized authority on subsidence. Of particulaz note with respect to this South of Divide permit <br />revision document, is the report prepared by Mr. Dunrud enfitled, Some Engineering Factors <br />Controlling Coal Mine Subsidence in Utah and Colorado (Dunrud 1976). In that report, Mr. <br />Dunrud evaluated subsidence in the Mesaverde Formation at the Somerset Mine, less than two <br />miles from the West Elk Mine. <br />Working closely with Mr. Dunrud, WWE has adopted the following multi-faceted approach to <br />quantifying subsidence in the permit area: <br />1. The existing longwall panels at the mine site have been extensively monitored and WWE <br />has evaluated the relevant data. These data provide the basis for Mr. Dunrud's conceptual <br />model, which is described later in this pernut text and in Exhibits 60 and 60B. Please note <br />that Exhibit 60 addresses the Apache Rocks and Box Canyon mining areas and Exhibit <br />60B specifically addresses the South of Divide mining area. (Exhibit 60C addresses the <br />subsidence and geologic hazards for the West Flatiron lease tract). <br />2. WWE has utilized a computer model to quantify subsidence, and this model has been <br />calibrated using the data collected at West Elk Mine. The model was developed by Dr. Syd <br />Peng and Dr. Yi Luo at West Virginia University and is referred to as the "Comprehensive <br />and Integrated Subsidence Prediction Model (CISPM)." <br />3. WWE has thoroughly reviewed the literature regarding subsidence and associated <br />hydrologic consequences. We have checked the fmdings associated with Mr. Dunrud's <br />conceptual model and the CISPM model with findings from case studies as described in the <br />literature, and we have concluded that the results are consistent. <br />4. Finally, subsidence projections described herein have been cazefiilly reviewed by Mr. <br />Dunnrd for reasonableness. Mr. Dunrud has visited the West Elk Mine azea on many <br />occasions and he is familiar with key factors pertaining to subsidence as they relate to the <br />South of Divide and other active mining areas. Consequently, Mr. Dunrud is well <br />qualified to draw conclusions about the nature of subsidence that is likely to occur. <br />Subsidence Survey - 2.05.6(6)(b)(iii)(A) & (6)(el <br />The following information documents subsidence processes that have been observed from studies <br />above longwall mining panels in the current West Elk Mine permit azea. The subsidence data <br />obtained in the current West Ells Mine azea have been used to project subsidence processes, <br />amounts, and effects into the Apache Rocks and Box Canyon mining areas, and South of Divide <br />2.05.95 RevisedJwie 1005 PRIG <br />