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of excess spoil would be generated. The applicant used a swell factor of 19.8 percent based on actual pre-mining and post-mining volumes using a computer program called STOCK. The excess spoil volumes were generated from a 148.58 acre area depicted in Figure 12-1x. A fill was designed for compliance with Rule 4.09.1(3). PCC proposed to open a box cut adjacent to an ephemeral drainage. Excess spoil was proposed to be disposed of in this drainage. The applicant submitted slope stability analyses for this fill area on Pages 12-13 through 12-17. Cross-sections and diagrams were submitted on Exhibits 12-ES1, 12-ES2 and 12-ES3. Computer data were submitted in Appendices of Tab 12. Slake durability analyses were submitted in Appendix 12-5. The applicant applied appropriate slope stability analyses using two computer programs, the SWASE program (Sliding Wedge Analysis of Sidehill Embankments) and the REAME program (Rotational Equilibrium Analyses of Multilayered Embankments). Computations indicated that the minimum factor of safety was 1.6 static and 1.27 seismic, which were within the requirements for long-term stability. An underdrain and a lateral drain to drain the seeps and springs within the drainage were proposed. Drainage designs were found in Table 12 and were based on measured and projected flow rates. PCC stated that the drain would be constructed of natural sandstone rock no larger than 5 feet in diameter and that no more than 10 percent of the rock would be less than 12 inches in size. The applicant further stated that the drains would be free of coal, clay or shale. The toe of the underdrain was designed to discharge into the coal seam, and the applicant stated that during wet periods the coal seam may not absorb all of the underdrain flow. Ground water levels within the underdrain would rise and then flow into the existing spoils, resulting in possible base saturation of the existing spoils. The stability of the existing spoils was not addressed in the revision application, and the Division determined that any discharge which may result in base saturation should be alleviated or addressed in terms of geotechnical stability. MLRD field observations indicated that there was an existing enclosed impoundment which exhibited swampiness in the area where the drainage ended. This impoundment was located at the toe of the proposed fill. Therefore, a stipulation was attached to the permit revision approval requiring that "WITHIN 90 DAYS OF THE PERMIT APPROVAL THE APPLICANT SHALL SUBMIT AN ADEQUATE DESIGN FOR A SURFACE DISCHARGING DRAIN TO BE CONSTRUCTED AT THE TOE OF THE PROPOSED FILL. SHOULD THIS SURFACE DRAIN FLOW INTO AN EXISTING SURFACE DRAINAGE SYSTEM THE APPLICANT SHALL DISCUSS THE EFFECT ADDITIONAL FLOW WILL HAVE ON THE HYDROLOGIC SYSTEM." Peabody Coal Company submitted the required designs within the 90 day timeframe, thereby resolving the requirements of the stipulation.