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Andreas fault MCE's). <br /> 5.3.3 FINAL COVER SLOPE STABILITY <br /> The final cover for the proposed development is anticipated to be a multi-layer <br /> system that, from top to bottom, will consist of the following: 1-foot thick <br /> vegetative soil layer; drainage layer; 60-mil thick HDPE geomembrane, textured <br /> on both sides; 1-foot thick compacted clay layer with maximum permeability of <br /> 10-6 cm/sec and;2-foot thick compacted foundation,layer. The proposed final <br /> cover will have a slope gradient of°31 (H:V) between benches that will be <br /> installed on 40-foot vertical intervals. Recognizing that a,drainage layer will: <br /> preclude development of pore-water pressures, the interface between the <br /> vegetative soil layer and the underlying,textured HD-PEjs considered the critical <br /> potential failure surface. <br /> 5.3.3.1 ANALYTICAL METHODS <br /> As shown in Appendix E, the semi=infinite•�slope-anaiysis-,procedure was-used to <br /> evaluate the stability of the final cover slope. Slope stability was evaluated for <br /> both static and seismic loading conditions. Since laboratory tests have not been <br /> performed to obtain shear strength parameters for the textured HDPE/vegetative <br /> soil interface, the analyses were directed to "back-calculate" the strength <br /> properties that will be required to .,de a-static- of safety of 1 5: Tris <br /> information will then be used to establish minimum criteria for later construction <br /> of the final cover. <br /> 5.3.3.2 FINAL COVER RESULTS <br /> As shown in the attached calculations, the results of the semi-infinite slope <br /> analyses indicate that a static factor of safety of 1.5 can be obtained for the <br /> proposed final cover configuration providing that the interface between textured <br /> HDPE and the vegetative layer above it or clay below it develops an angle of <br /> friction of 27 degrees with no cohesion (i.e. � = 27° and c= 0). Review of the <br /> native soil data generated in the area by CH2MHill (1992) suggests that the <br /> required interface strength parameters can be achieved. <br /> The pseudo-static analyses that were completed to evaluate the final cover <br /> figuration indicate a yield acceleration of 0.15 g for these interface parameters. <br /> Forward Landfill JTD 5-16 <br /> L:\Allied\2000.193\Reports\finaljtd:Sec-5.0:08/22/01 <br /> RCtVAN O.RTIOOAT 1C AR4f1 P`I ATF4 <br />