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0 <br />• INVESTIGATION <br />Our investigation consisted of observation of fill areas, observation and sampling <br />of 13 test pits, and laboratory testing. Several test pits were existing cuts exposing <br />native soils. Representative samples of typical alluvial and colluvial soils and bedrock <br />were obtained. To evaluate the proposed spoil, bulk samples were obtained from test <br />pits or road fills derived from the bedrock. <br />We have performed two previous Stability Evaluations for Portal Areas and Small <br />Sedimentation Ponds (see references). These investigations included 14 test <br />pitlsampling locations and laboratory testing and analysis and provide valuable <br />additional information which was considered in this investigation. Laboratory data from <br />the previous investigations is provided in Appendix E and stability analysis for the small <br />sedimentation pond embankments in Appendix D. <br />Subsurface Conditions <br />• . <br />Soil conditions vary over short distances due to the steep topography. Soil <br />cover ranges from zero to over 25 feet in the main drainages. The typical soil types <br />found range from clayey sand to sandy clay with moderate plasticity. The soils were <br />grouped into colluvial and alluvial soils based on topography; the laboratory testing <br />indicated reasonably similar engineering properties for each group. Laboratory test <br />results are presented in Appendix B. Occasional cleaner sand, gravel or cobble soils <br />occur in main drainages. These soils do not affect stability of fills. Bedrock consists <br />of hard sandstone and shales with coal/lignite seams. <br />The soil cover in excess spoil fill and pond areas is typically 6 feet or less. Ten <br />feet of clay was found in TP-6A in the lower, flatter area near the toe of Fill 6. In <br />Lorencito Canyon up to 12 feet of clay soils was found in CPT-3, in a moderate sloping <br />• LORENCITO COAL COMPANY, LLC <br />LORENCITO SURFACE MINE-PHASE I 6 <br />CTLlT 32, 611 <br />