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3. Textured HDPE geomembrane-GCL interface <br />4. Internal shear plane within the GCL <br />5. GCL-subgrade interface <br />The slope stability of the sideslope liner system is of concern only during the period <br />between its installation and until the liner is buttressed by waste placement in Module 1. <br />Because this is a temporary condition, a factor of safety of 1.25 is considered acceptable <br />for the sideslope liner stability. Based on infinite slope stability analysis', for a factor of <br />safety of 1.25 against sliding of the sideslope liner system, the above critical shear planes <br />should meet a shear strength defined by a friction angle of 22.6 degrees. With the use of <br />a high-density polyethylene (HDPE) geomembrane that is textured on both sides and a <br />shear -reinforced GCL, this shear strength can be achieved because of the low normal <br />stress levels involved (0-500 pounds per square foot [psf]). <br />3.4.2 Potential for Liner Uplift <br />The groundwater table at the site is located approximately 150 feet below the proposed <br />lowest base elevations within Module 1. Therefore, potential for liner uplift can exist <br />only if perched groundwater conditions are encountered. Perched groundwater condition <br />should be investigated during liner construction and appropriate remedial measures <br />should be taken (e.g., providing a pore water relief system), if required. <br />mvelmr rr- • $ rI <br />3.5.1 Critical Cross -Sections <br />As noted previously, the northern perimeter of Module 1 is along the existing landfill, <br />therefore, no waste slope will exist along this perimeter when Module 1 is filled. Waste <br />slopes will exist along the western, southern, and eastern perimeters of Module 1 (these <br />slopes will be filled over during filing in the future modules). The heights of toe buttress <br />available for the waste slopes along these three perimeters vary. Also, the <br />directions/magnitudes of base liner slopes perpendicular to the perimeters are different <br />for all three perimeters. Therefore, three different cross-sections were selected to analyze <br />slope stability of Module 1. The cross-sections are designated as AA, BB, and CC. The <br />locations of these three cross-section are shown in Figure 2 (and also in Attachment 1). <br />8'= tan"' (1.25 x 0.33) = 22.6 degrees <br />\\SACRFPI\COMMON\sacDP\2002\PRJ\PJ8\83\835608.2bz.doc <br />3-3 <br />EMCON/OWT, Inc. <br />Rev. 0, 07/31/02 <br />