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(ROIOgteal rcckaus Ifia Page 6 <br /> Valley wholesale Drug Company <br /> Project No 989 2 <br /> November 8,2004 <br /> 2.5.3 Site-Specific Hydrogeology <br /> A site map showing the locations of streets, structures, wells, and other site-related details is <br /> ' attached as Figure 2 The approximate locations of shallow subsurface utilities are shown in <br /> Figure 3 <br /> ' 25.3.1 Lithology and Soil Characteristics <br /> The August 23, 2004 GeoProbe investigation incorporated the findings of previous soil <br /> investigations conducted at VWDC <br /> ' The litholo of the site can be divided into 3 generalized sections <br /> gY <br /> • Surface to 23-feet bgs—primarily comprised of brown to dark brown clays, silty-clay <br /> ' and silty-sandy-clay mixtures <br /> • 23-to 31-feet bgs—primarily comprised of brown sandy-clay <br /> ' • 31-to 42-feet bgs—pnmanly compnsed of dense,plastic "blue-grey" clay <br /> The Site Conceptual Model dated December 17, 2003 discusses the lithology and site <br /> tcharacteristics in more detail <br /> 2.5.3.2 Groundwater Gradient and Bearing <br /> Site-specific groundwater bearing and slope, as measured during the third quarter of 2004, <br /> are N44°W and 0 0059 ft/ft respectively The average horizontal groundwater bearing for the <br /> site is N30°W with an average gradient of 0 0065 ft/ft Horizontal groundwater elevation, <br /> tbearing and gradient data are summarized in Table 3 of Appendix A <br /> The vertical groundwater gradients are generally negative, or downward, and approximately <br /> one order of magnitude greater than the horizontal groundwater gradients The average <br /> vertical groundwater gradient is negative 0 0134 ft/ft Vertical groundwater gradient <br /> calculations have been performed at regular intervals since July of 2002 and are summarized <br /> ' in Table 4 of Appendix A <br /> i <br /> ' 2.5.3.3 Average Groundwater Velocity <br /> Hydraulic conductivity and porosity were calculated from three soil samples collected during <br /> the installation of MW-101 in March 2003 The soil samples were collected from 21, 26 and <br /> 41 feet bgs The laboratory data is included in Appendix C of the 3rd Quarter 2004 — <br /> ' Groundwater Monitortng Report dated October 4, 2004 <br /> ' The following conclusions were formed based on the equation v=K Un <br /> • n=effective porosity <br /> • K= average hydraulic conductivity <br /> ' • i=average hydraulic gradient (site-specific average is 0 0065 ftlft) <br /> • V=average horizontal groundwater velocity <br />