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• The maximum and average overburden conditions at Areas 2, 3, and 4 result in ratios ranging from 0.90 to 0.97 and, therefore, do not meet requirements for either thin or thick overburden. All excavated non-coal material from the mining areas will be used for backfilling the mined pits and blending mined areas into the existing topography to achieve the approximate original landfonn. Therefore, no excess spoil material will exist. Since mining operations have been performed with scrapers and dozers at Nucla, the postmining topography was estimated based upon a 15 percent swell factor. The proposed revised postmining topography at Nucla was generated based on actual (existing) contours. It was assumed that all swelling of the material has been accomplished. Further handling of the material could cause additional swelling, but compaction caused by reclamation equipment would offset any difference in volume. The postmining topography map was created by generating cross sections through the mined • area, balancing the available non-coal material and generating a contour map to provide a landfortn surface compatible with the postmining land use, pre-existing drainage patterns and to provide a stable landfomt surface. After the initial postmining contour map was developed, the existing and proposed surfaces were volumetrically compared with the aid of a computer program called SURFER. The postmining contour map was adjusted until the difference between fhe cut and fill volume was less than one percent. Typical cross sections through the mining areas are shown on Exhibits 20-4 (Nucla-10 sheets). These cross sections show existing, original, and postmining ground. The areas mined and coal seams remaining are also shown on the Nucla Mine cross sections. Cross sections A-A' through E-E' (Exhibit 20-4) at Nucla reflect the proposed postmining land surface for Mining Area No. 1. The grading in this area will allow for irrigation in the future, although Peabody does not propose to irrigate or construct the irrigation laterals. Please refer to Appendix C, Tab 20 for discussion of the reclaimed drainage channel, and Exhibit 20-5 for the drainage profile K-K'. Appendix C also shows the SEDCAD output for this channel. Mining disturbance in Mining Area No. 2 was restricted to the vicinity of cross section F-F'. The premining line depicts the ground as it was prior to the redisturbance in that area. The postmining line depicts the ground as it currently exists (reclaimed). The remaining cross 20~