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August 1994 -7- 933-2713.003 <br /> 4.3 Laboratory Testing <br /> 4.3.1 Analysis <br /> Laboratory analysis was performed to determine the vertical permeability (hydraulic <br /> conductivity) of the subsurface soils. Four samples were collected for flexible wall permeability <br /> testing (ASTM D5084): BH-2 at 37 feet (clayey gravel), BH-2 at 61 feet (clayey gravel), BH-3 <br /> at 78 feet (clayey gravel), and BH-5 at 47 feet (clay). <br /> 4.3.2 Results <br /> The laboratory permeability results are shown in Table 3. They yield an average value of <br /> approximately 3 x 10-g cm/s for the hydraulic conductivity of the clayey gravel. <br /> Although these represent vertical rather than horizontal permeabilities, experience indicates that <br /> horizontal permeabilities will be no greater than about 100 times the vertical permeability or <br /> about 3 x 10' cm/sec. The clayey gravels therefore exhibit a hydraulic conductivity which is <br /> about 10 to 100 times lower than the hydraulic conductivity of the sandy gravel zone. <br /> 4.4 Discussion <br /> Hydraulic conductivity of clean, sandy gravels is generally about 1 x 10-2 cm/sec, based on <br /> experience. The hydraulic conductivity results for the sandy gravels in Cement Creek are much <br /> lower than 1 x 10-2 cm/sec, suggesting that the sandy gravels are not clean but rather have <br /> significant fine-grained material such as clay and silt occupying the pore spaces. Observations <br /> made during slug testing confirm the presence of significant fine-grained matrix material in the <br /> gravels. During slug testing, it was noted that the piezometers had significant silt within the <br /> casing, despite the use of small slot-size (0.010-inch slots) and sand packs. Based on the slug <br /> test results and field observations, the sandy gravels within Cement Creek are not clean but <br /> Golder Associates <br />