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1 <br /> <br />Assumed Reclamation Grade <br />' For the 2000 AHR, the remaining LTSP overburden volume was estimated using the following <br />two surfaces: <br />' 1. The October 2000 Facility Topographic Surface. This topographic surface is based on <br />aerial photography and topographic mapping conducted by Cooper Aerial Survey <br />' Company from Tucson, Arizona. <br />2. The Final Reclamation Surface. This surface was based on the fmal reclamation grade <br />' defined in the permit and 2000 AHR (Appendix Q-1, Reclamation Contour and <br />Drainage Plan Map). <br />' Review of the project file indicated that the previous LTSP overburden volume, as reported in <br />the 1999 AHR, was calculated using: <br />1. The October 1999 Facility Topographic Surface. This topographic surface is based on <br />aerial photography and topographic mapping conducted by Cooper Aerial Survey <br />Company from Tucson, Arizona. <br />' 2. The 4800-Foot Elevation Contour. This contour was selected as an average final grade <br />with the contour artificially closed on the west side of the LTSP. <br />' The 4,800-foot elevation contour was selected, based on best engineering judgement, as the <br />average final reclamation grade. An average grade was selected to simplify the LTSP <br />overburden volume calculation and allow for timely and reproducible calculations using <br />' available computer modeling (i.e., Softdesk/Adcadd Software Civil/Survey, with Earthworks <br />and Digital Terrain Modeling Modules). However, the assumed 4,800-foot elevation contour <br />is significantly higher than the fmal reclamation grade. The final grade slopes northeast from <br />' the 4,800-foot elevation contour down to the 4,780-foot elevation contour. This reclamation <br />surface allows for drainage from the LTSP to the west perimeter ditch and then to Sediment <br />Pond 2. The difference between the assumed 4,800-foot elevation contour and the final <br />' reclamation grade contributed to the volumetric discrepancy between 527,000 bcy and 331,200 <br />bcy as reported in the 2000 and 1999 AHR, respectively. <br />' Volume Calculation Method <br />For the 2000 AHR, the remaining LTSP overburden volume was computed using the Grid <br />' method provided in the AutoCAD Land Development Desktop software. However, previous <br />LTSP overburden volumes have been calculated using the Average End Area method provided <br />in the Softdesk/Adcadd Software Civil/Survey, with Earthworks and Digital Terrain Modeling <br />' Modules software. In general, the Grid method provides a more precise method for volume <br />estimation compared to the Average End Area method. These two methods are described <br />' below. <br />LJ <br />' z BEAK/TerraNeKt <br />