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natural subsurface environment. The aquifer located beneath <br /> the site is neither isotropic nor homogeneous. It exhibits <br /> variations in physical properties both vertically and <br /> horizontally. Therefore, the hydraulic conductivity <br /> determined by the aquifer test data should only be considered <br /> accurate within an order of magnitude of actual values at the <br /> specific point within the porous medl_a. Based on the <br /> calculated hydraulic conductivity of 3.167 foot per day, the <br /> actual hydraulic conductivity could range from 0.0167 to <br /> 1.67 foot per day. This range of hydraulic conductivity <br /> values is typical for loam soils composed of a mixture of <br /> _ clay, silt, sand, and organic matter, which is consistent <br /> with the silt/clay mixture encountered at the site. <br /> It should be noted that plume migration does not necessarily <br /> occur at the same rate as ground water movement. Darcy's Law <br /> governing ground water flow does not consider the <br /> hydrodynamic processes of adsorption and dispersion that are <br /> involved in the transport of contaminants in ground water. <br /> 8.0 FINDINGS AND CONCLUSIONS <br /> ^� The findings and conclusions based on the results of this <br /> N subsurface investigative work performed at the site, aswell <br /> as previous work by other consultants, are summarized below: <br /> w The predominant sail types at the site are clay--silt <br /> mixtures with lenses of sand and gravel. <br /> a The average hydraulic conductivity of the aquifer <br /> material at the site as determined by the slug test <br /> method is 0.051 meter/day, or 0.167 foot/day. The <br /> r calculated average linear velocity of a fluid <br /> particle moving in the aquifer is 0.305 foot per <br /> f year, <br /> • The average depth of ground water is approximately <br /> A 5.8 feet below grade, which could vary with seasonal <br /> conditions. <br /> e The general ground water flow direction is to the <br /> north/northwest, with an wverage gradient of 0.005 <br /> foot per foot. Previous ground water monitoring at <br /> the site indicated changing ground water flow <br /> directions. These changes in flow direction are <br /> probably due to past dewatering activities. <br /> - J <br /> 16 <br />