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<br />• sizes. This is magnified in the direct shear testing since +3/8-inch particles were <br />removed and not replaced. The effect is the test results represent the finer matrix <br />material in the spoil. Also shown are the normal and lower bound values used in the <br />analysis. Considering the limitations of the sampling and testing these are considered <br />conservative values. <br />Four direct shear tests were performed on clay and clayey sand overburden soils <br />(Fig. C~}. The normal and lower bound strengths used are also shown. These values <br />are consistent with our experience, published values and the classification of the soils. <br />Our experience indicates the sedimentary bedrock possesses sufficient strength <br />so that failure through the bedrock is not a consideration. <br />RESULTS OF STABILITY ANALYSIS <br />Excess Spoil <br />The stability analyzes were performed using the Spencer method and are <br />summarized on Table C-1. Normal parameters were selected for strength and density. <br />For this condition a factor of safety of 1.9 was calculated. Infinite slope analysis with <br />a 3:1 average slope results in a factor of safety of 2.0. The spoil and clay properties <br />were varied as shown on Fig. C-5. The lowest factors of safety calculated was 1.4 for <br />the lower bound clay strength. <br />The effects of water buildup within the fill were evaluated by simulating water <br />buildup to two levels as shown on Fig. C-I. The worst case water conditions (extending <br />to the toe) show low factors of safety for slump failures near the toe (1.3). This analysis <br />result is expected and indicates that drainage and control of subsurface water are <br />critical near the toe. The less severe water conditions indicate factors of safety on the <br />• LORENCITO COAL COMPANY, LLC <br />LORENCITO SURFACE MINE - PHASE I 1 O <br />CTLR 32, 617 <br />