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AWL <br />City of Stockton A68102.02A <br />June 14, 1996 Page 3 <br />The soil sample analytical results are summarized in Table 2. <br />TABLE 2 <br />Summary of Soil Sample Analytical Results <br />Sampling Date: April 25, 1996 <br />Sample <br />Depth Interval <br />Material <br />Proctor Test <br />Permeability <br />cm/s <br />Number <br />(feet BSG) <br />Description <br />R-1 <br />0 to 2.5 <br />Clay <br />optimum Moisture = 17.9% <br />8.2 X 10"9 <br />Maximum Dry Density = 111.4 pcf <br />R-2 <br />0 to 3 <br />Clay <br />optimum Moisture = 17.0% <br />6.0 X 10"9 <br />Maximum Dry Density = 113.6 pcf <br />R-3 <br />4 to 11 <br />Clayey Sand <br />optimum Moisture = 17.1% <br />3.2 X 10-8 <br />Maximum Dry Density = 108.0 pcf <br />BSG = below site grade <br />pcf = pounds per cubic foot <br />cm/sec = centimeter per second <br />6 <br />Consistent with the requirements of the California Code of Regulations, Title 23, Article 4, <br />Section 2541, the criteria for permeability of a Class III Landfill final cover material is less <br />than or equal to 1 X 10-6 centimeters per second (cm/sec). As Table 2 indicates, the <br />composite samples collected from material between the surface and 2.5 feet BSG had a <br />primary permeability that was lower than the statutory requirements. The organic clay <br />material observed in the field between the surface and 2.5 feet BSG was present in all eight <br />pits. Therefore this material is assumed to cover the whole surface of the tested site. Based <br />on that assumption, the volume of material available on the tested site between the surface <br />and 2.5 feet BSG is estimated to be 510,000 cubic yards. <br />The presence of prismatic structures formed by fractures in the organic clay material <br />(between the surface and 2.5 feet BSG) which was observed in the field, appear to be <br />desiccation features. The formation of these features may create conduits for liquid flow. <br />This phenomenon is termed "secondary permeability". The assessment of secondary <br />permeability was beyond the scope of this investigation. <br />The material located between 2.5 and 11 feet BSG may also be suitable for use as a final <br />cover based on its primary permeability. Based on the assumption this material is present <br />beneath the entire tested site, the volume of material in this interval is estimated to be <br />1,700,000 cubic yards. However, there was clayey gravel observed in pit P-4 and the volume <br />of this clayey gravel is unknown. The clayey gravel would not be suitable for use as final <br />