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0 <br />STABILITY ANALYSIS <br />Summary <br />Stability of a conservative excess spoil fill configuration, area and contour fill <br />configuration, and sedimentation embankments was performed. We previously <br />analyzed in detail two excess fill configurations on a preliminary basis (Job No. 25,251). <br />This provides additional confirmation of our results. Sedimentation pond embankments <br />of the same type planned were analyzed in a previous investigation (Job No. 26,559). <br />We have relied upon these in ourjudgement and recommendations. Results of stability <br />analysis for excess spoil are presented in Appendix C. <br />The geometry we used was biased towards worst case topography, and <br />conditions at most excess spoil fills will be more favorable. The strength parameters <br />'~ selected are considered conservative. The relatively flat slopes proposed for the spoil <br />• fills of 3:1 (H:V) would be expected to result in favorable stability conditions, unless <br />very poor foundation materials are present or water develops in the fill. This is <br />confirmed by our analysis. Poor foundation conditions were not found in our <br />investigation. Ground water accumulation will be controlled by drains. To summarize, <br />the stability analyses indicate the proposed locations and configurations result in stable <br />fill meeting CDMG requirements. <br />Our analysis of surface area mining fills and contour mining backfill indicates a <br />stable fill with a 2.5:1 (horizontal:vertical) slope to heights up to 250 feet. <br />Based upon soil conditions found in this investigation, the previous stability <br />analysis for small sedimentation ponds is considered appropriate for the proposed <br />embankments below excess fills (Appendix D). <br />• LORENCITO COAL COMPANY, LLC <br />LORENCITO SURFACE MINE -PHASE 1 <br />CTLIT 33, 611 <br />8 <br />