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The FSCR depends on the mass per unit area of the geotextile cushion. Assuming a 16,oz/yd2 <br /> (540 g/m2)geotextile, <br /> FSCR = 1.2 <br /> Assume,a factor of safety of 2 for chemical and biological degradation, <br /> FscsD =2.0 <br /> Substituting the above values in eq. 1, <br /> [50+0.00045 540 1 1 10,000 kPa <br /> (0.00635)2 (1.0)(0.5)(0.5)- (1.2)(2.0)- <br /> Assuming <br /> 1.2)(2.0)Assuming a conservative maximum waste height of 150 feet in Module 4 and a waste unit <br /> weight of 65 pounds per cubic feet,the actual pressure(Paw)on the geotextile cushion is, <br /> Pa,wal _(150 ft)x(65 lb/fft)=9,750 lb/ie=470 kPa <br /> The factor of safety(FS)against puncture of the HDPE geomembrane is given by, <br /> FS = Parr°w _ 10,000 = 21 <br /> Paan,,, 470 <br /> Since the computed factor of safety is greater than the recommended (Koerner, 1998) minimum <br /> factor of safety of 3, the 16-oz/yd2 geotextile cushion(non-woven, needle-punched) is more than <br /> adequate to provide the necessary puncture protection. <br /> 3.0.Geotextile Cushion Interface Shear Strength <br /> The results of slope stability analyses for Module 4 were previously presented in a report entitled <br /> Static and Seismic Slope Stability Analyses, North County Recycling Center and Sanitary <br /> Landfill, Module 4(EMCON/OWT, July 2002). The results of that slope stability analyses show <br /> that Module 4 base liner system must meet a minimum residual shear strength defined by a <br /> friction angle of 10.5 degrees to achieve the minimum factors of safety against slope instability. <br /> In addition to the interfaces noted in the above-referenced report, the interface between the <br /> geotextile cushion layer and the 60-mil textured HDPE geomembrane must also meet this shear <br /> N:1sacDP120031Prj183\835608.3ap.doc <br /> (NCRCSL) <br /> 3 <br />