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C7 <br />Therefore, it is concluded that no permanent displacement will take place along the most <br />critical slope stability cross-section during the MPE, as long as the liner systems satisfy <br />the static strength requirements. <br />5.1.4 Liquefaction Potential <br />Because the groundwater table is located at a depth of more than 150 feet below the <br />ground surface and the foundation soils consist of hard sandy silt and clay, it is concluded <br />the potential for liquefaction of the landfill foundation does not exist. <br />5.2.1 Base Liner Shear Strength and Testing Requirements <br />Based on the results of static/seismic slope stability analyses presented in this report, the <br />base and sideslope liner system should meet a minimum residual shear strength envelope <br />(both interface and internal) defined by a friction angle of 10.5 degrees within a normal <br />stress range of 0 to 12000 psf. This shear strength is achievable with proper selection of <br />the geocomposite drain, textured HDPE geomembrane, and GCL products. The shear <br />strengths of geocomposite drain -textured HDPE geomembrane interface, GCL-textured <br />HDPE geomembrane interface, and internal shear strength of the GCL should be verified <br />using direct shear testing (ASTM D5321/D2543). The testing should be performed <br />under: <br />• Normal Stresses: 3,000, 6,000, and 12,000 psf <br />• Strain Rate: 0.2-inch/minute for test involving geocomposite <br />0.04-inch/minute for test involving GCL <br />• Minimum Displacement: 3 -inches <br />• GCL Hydration: 48 hours under each normal stress <br />The residual shear strength should be that measured at a shear displacement level of <br />three inches. It is important that the shear strength of the aforementioned critical shear <br />planes be verified during the selection of the geocomposite drain, the textured HDPE <br />geomembrane, and the GCL products. Additional testing should be performed on actual <br />materials to be used in the liner construction, prior to installation. <br />® \\SACRFPI\COMMON\sacDP\2002\PRJ\PJ8\83\835608.2bz.doc EMCONIO T, Inc. <br />Rev. 0, 07/31/02 <br />5-2 <br />