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coal thickness, bottom of the mined seam, original ground surface elevations, and the limits of the area to <br />be mined. All of these data are available in a computerized drill hole database and from topographic maps. <br />Volume Calculations (Preminino Tooooraohvl. All of the volumetric calculations used in the development <br />of the Postmining topography are shown on Table 20-1, Postmining Landform Mass Balance (North <br />Area) and 20-1A, Postmining Material Mass Balance - II-W South Area. Please refer to Figure 20-1, <br />Postmining Topography Typical Mass Balance, for a sketch of the volume locations. The following <br />methods were used in determining those volumes. <br />Premining Material Volume. A computer model developed by Peabody called STAMP was used to <br />determine the Premining material volume. All pertinent drill hole data is input into the model: location, <br />depth, seam thickness, overburden thickness and stratigraphy, quality, hole elevation, etc. With this <br />information, the computer model cam determine volumes of material by pit, mining block, year, or the entire <br />mining area. The volume determined, in this case, contains all the material, from the ground surface to <br />the coal seam bottom within the boundary of the area to be mined. <br />Virgin Overburden Material Volume. STAMP is again used to determine the volume of material between <br />the original' ground surface and the tap of the coal seam to be mined. <br />Total In-Place Coal Volume. This is the difference between the Premining material volume and the virgin <br />overburden material. <br />Recoverable Coal Volume. It i;> estimated that the actual recovery rate at Seneca II-W will be <br />approximately 1,650 tons per acre foot (TPAF) or 93.6 percent of theorical density (1,762 TPAF). The <br />recoverable coal volume is determined by multiplying the in-place coal volume by the actual recovery <br />rate.Non-Recovered Coal and Parting Material Volume. This is the difference between the recoverable <br />coal volume and the total in-place coal volume. <br />Premining Overburden Volume. If there is non-recovered coal, then it stays within the pit area. Therefore, <br />this material is added to the virgin overburden to determine the Premining overburden volume. <br /> <br /> <br /> <br />PR-05 6 Revised 01/06 <br />