2013-04-10_PERMIT FILE - C1981019 (78)

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Collom Area Geology Pre - Feasibility Report needed and the modeling process was repeated. The final geologic model was constructed after several modeling iterations. Suites of geologic cross sections, coal isopachs, roof structures, and various vertical geologic ratio maps were generated at the conclusion of the modeling process. These maps are included in electronic format (PDF) in Appendix I. 7.4 Coal Quality Model The coal quality for Colowyo was also modeled across the entire project area using StratModel. The coal quality model grid surfaces were built using dry basis data. Approximately 297 drill holes were used to build the coal quality model. The coal quality modeling included quality parameters of total moisture, equilibrium moisture, ash, heating value (Btu /Ib), total sulfur, ash fusion temperature (reducing spherical), apparent specific gravity and calculated apparent specific gravity. All of the seams included in the StratModel were also modeled for coal quality, with the exception of the Y95, Y85, Y75, Y65, Y55, Y45, Y35 and the HO seams. These are generally minor seams and contain limited (fewer than three valid points) coal quality data. In addition to the dry basis coal quality model, models for as- received basis and equilibrium basis moistures were created. These models exist in MineScape as suites of expression surfaces that factor moisture surface values into the dry basis ash, Btu /Ib and sulfur surfaces. This provides great flexibility in utilizing the coal quality data. Coal quality model construction consisted of exporting incremental ply data from the drill hole database and importing the data into MineScape. Composite coal quality values were then created by cross referencing the ply data against the coal seams in the stratigraphic model. The resultant composite values were then gridded using the MineScape "FEM" interpolator. Coal quality contour maps August 2005 Page 29 of 38