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Drainage Conditions <br />The Refuse Disposal Area has been constructed with drains along the sides of the fill to allow <br />for surface runoff to drain from the felt. Diversion of surface drainage around the spoil will limit the <br />amount of water entering the fill. We believe the permeability of the fill to be low and saturation through <br />precipitation unlikely because this area of Colorado is relatively dry. We believe the water present in <br />the fill is draining slowly. There is reportedly an underdrain which runs the length of the fill. During <br />our visit there was some apparent drainage down the face of the pile which was runoff from the top <br />of the fill. We did not notice drainage out of the face. We believe most of the fill is relatively dry with <br />the exception of the top 20 to 25 feet. <br />Method of Analvsis <br />Our stability analyses for cross section A were performed using the program Geoslope (tm) <br />developed by Geocomp Corp. This computer program is based upon the slope stability analysis <br />procedure STABL developed at Purdue University. Geoslope offers Modified Bishop Analysis Methods <br />for circular-shaped failure surfaces and Janbu's Method of Generalized Slices for non-circular surfaces. <br />The analysis employs a limit equilibrium procedure of slices. We believe the numerical values selected <br />for strength of the various materials and the water surface assumptions control the computed factor <br />of safety. We have performed a parametric study using conservative values of strength conditions in <br />order to assess slope stability. The following paragraphs describe the results of the analyses. Figure 4 <br />and Table D-1 summarize the parametric studies; analysis results are contained in Appendix D. <br />April 1991 <br />Wyoming Fuel Company provided a profile and topographic data for April of 1991. We <br />assumed a layer of wet material from depths of three to twenty-five feet. The foundation material was <br />8 <br />