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West Elk Mne <br />. The focus of Exhibit 60B is on the South of Divide Mining Area. It is not feasible to quantify <br />subsidence by reference strictly to the Permit Revision Area; to the contrary, it is necessary to evaluate <br />the relevant panels in their entirety. Exhibit 60 addresses subsidence in the Apache Rocks and Box <br />Canyon mining aeeas. Since mining activities are continuing in these areas, Exhibit 60 has been <br />retained in the permit. The discussions in this section, however, focus on the South of Divide mining <br />azea, as the primary future mining azea, but retain discussion of subsidence pazameters for the Apache <br />Rocks, Box Canyon, and West Flatiron mining aeeas. <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 aeeas. Specifically, MCC has <br />retained Wright Water Engineers, Ina (WWE) of Denver to evaluate subsidence and probable <br />hydrologic consequences. WWE worked closely with Mr. C. Richazd 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 pemut <br />revision document, is the report prepazed by Mr. Dunrud entitled, Some Engineering Factors <br />Controlling Coal Mine Subsidence in Utah and Colorado (Dunrud 1976). In that report, Mr. Dunrud <br />evaluated subsidence in the Mesaverde Formation at the Somerset Mine, less than two miles from the <br />West Elk Mine. <br />Working closely with Mr. Dunrud, WWE has adopted the following multi-faceted approach to <br />quantifying subsidence in the permit azea: <br />1. The existing longwall panels at the mine site have been extensively monitored and WWE has <br />. evaluated the relevant data. These data provide the basis for Mr. Dunrud's conceptual model, <br />which is described later in this permit text and in Exhibits 60 and 60B. Please note that Exhibit <br />60 addresses the Apache Rocks and Box Canyon mining areas and Exhibit 60B specifically <br />addresses the South of Divide mining azea. (Exhibit 60C addresses the subsidence and geologic <br />hazazds for the West Flatiron lease tract). <br />2. W WE has utilized a computer model to quantify subsidence, and this model has been calibrated <br />using the data collected at West Ells Mine. The model was developed by Dr. Syd Peng and Dr. <br />Yi Luo at West Virginia University and is referred to as the "Comprehensive and Integrated <br />Subsidence Prediction Model (CISPM)." <br />3. WWE has thoroughly reviewed the literature regazding subsidence and associated hydrologic <br />consequences. We have checked the findings associated with Mr. Dunrud's conceptual model <br />and the CISPM model with findings from case studies as described in the literature, and we <br />have concluded that the results aze consistent. <br />4. Finally, subsidence projections described herein have been carefully reviewed by Mr. Dunrud <br />for reasonableness. Mr. Dunrud has visited the West Elk Mine azea on many occasions and he <br />is familiaz with key factors pertaining to subsidence as they relate to the South of Divide and <br />other active mining areas. Consequently, Mr. Dunrud is well qualified to draw conclusions <br />about the nature of subsidence that is likely to occur. <br /> <br />2.05-106 RevrredJum 2005 PRIG, Rev. March 2006; Rev. Apri12006 PRIO; May 2006 PRIG <br />