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1100318 R0T0 0811 JRW1 37 <br />survey performed as part of Exponent’s investigation (Appendix 46). The subsurface <br />stratigraphy is defined by the geologic map and cross sections contained in Appendix 39. <br />Based on Exponent’s field observations, photographs contained in the appendices, and the <br />aforementioned topographic data, cross section D-D' was selected as the most representative <br />section upon which to perform slope stability analyses to study the cause of the December 2, <br />2008 landslide. <br />5.3.1.2 Groundwater Conditions <br />Three groundwater levels for the confined groundwater conditions were defined for use in the <br />slope stability analyses: high groundwater, groundwater level approximated based on May 2011 <br />field measurements, and no groundwater. The levels were selected to study the effect on the <br />slope stability of different groundwater conditions. The groundwater level approximated based <br />on May 2011 field measurements (Appendix 44) assumes continuity of groundwater levels <br />between those measured in Area H and those measured in piezometer P-2. The high <br />groundwater level is based on an assumed groundwater level near the top of Area H and <br />extending up slope in a manner similar to but at a higher elevation than the level based on May <br />2011 field measurements. The “no groundwater” condition is comparable to a groundwater <br />condition as measured in May 2011 but with no substantial groundwater accumulation above <br />Area H in the ascending west highwall slope. <br />5.3.1.3 Material Properties <br />The material properties used in the slope stability analyses are based on laboratory test results <br />contained in Appendix 43. The interpretation of the clay bed strength parameters is also <br />contained in Appendix 43. As discussed in Section 5.2.4, the strength parameters used for rock <br />units present at the quarry are based upon the laboratory test results for the various zones of <br />quality of rock samples observed in the cores. Strength data at the lower end of the laboratory <br />measured values was used for the basal Manitou Formation (Omb) above the clay bed and <br />Area H ground surface, as discussed in Sections 5.2.3 and 5.2.4. For example, the quality of the <br />Manitou Formation was observed to be substantially lower at the bottom of the stratigraphic <br />profile because of compositional inhomogeneities, fracturing and discontinuities; as a result,