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DRAFT XVII. Backfillinq and Grading (2.05.3(3), 2.05.3(9), 2.05.4(2 2.05.4(2)(c), 4.09, 4.Z3, 4.14) - R PORTION - Appendix J of the amended permit application was prepared for the operator by Dames and Moore, Inc., and is entitled "Engineering and Hydrological Data Supplement for East Dump". This report presents the results of a hydrologic and geotechnical evaluation of the East dump proposed for permanent construction at the Bourg Strip mine. The report includes a geotechnical evaluation of the foundation site, including materials strength testing and a stability analysis of the proposed pile configuration. This analysis, prepared in keeping with the prudent state-of-the-art of slope stability analysis determines that even if the pile's material were saturated, a static slope safety factor of 1.5 could be achieved. The proposed design for the East dump calls for subtle, less than S:I (horizontal to vertical) slopes. "The general Land form of the East dump will be that of a rounded mound some 200 yards northeast of where a natural rounded mound stood before mining." (Page 11, Appendix J) However, insufficient data exists within the permit documents with which to quantify the expected overburden swell factors at the Bourg Strip. Without this information and an accurate determination of the volumes of coal removed from the pit, an accurate volumetric projection of the final post-mining topography cannot be completed. Lacking a definitive overall bulking factor, the consultant recommends that a swell factor of Z0~ be used until the actual value can be verified by field measure- ment. Two other mines have been permitted by the Division within several miles of the Bourg mine site. Both of these mines produce coal from the same bedrock formations which the Bourg Strip pit proposes to mine. Both of these approved permits project inherent overburden swell factors in excess of 20%, resulting in overall bulking factors in excess of 1.04. Therefore, both of these mine plans project minor excess spoil amounts. In order to project the relationship of excavated pit volume to backfilled swollen overburden volume at the Bourg Strip, Division personnel revised Table 4 of the permit application assuming inherent overburden swell factors of l0a and 200. In addition, Division personnel assumed an in-place coal density of 2150 pounds per yard2, as reported in the Caterpillar Handbook. Utilizing these assumptions, the Division projected a meterial balance for Stages I through IV of the proposed mine plan. These calculations project that an approximate balance of backfill versus excavated pit volume (overall bulking factor of 1.00) would occur if the average inherent overburden swell factor was 23.60. This suggests, based upon information developed and verified at the nearby permitted mines, that it is unlikely that significant excess spoil will result from the proposed mining operation at the Bourg Strip mine.