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r <br /> investigations, approximately 5 cubic yards of TPH-D impacted soil are estimated to remain on <br /> the site <br /> i <br /> y substantial migration of TPH_D in soil or groundwater is not anticipated because these <br /> contaminants adsorb to soil, and because bacteriologic degradation is probably sufficient to <br /> contain any desorbed TPH-D analytes in this small, very low concentration plume Utilities are <br /> depleted in Figure 10, none of which are considered to be migration pathways due to their <br /> shallow depth or location <br /> r 5.0 Local and Regional Hydrogeology <br /> Groundwater at the site has been encountered at depths ranging from 9 29 feet to 14 feet bsg, <br /> with an average depth to groundwater measured in both sampling events of 10 67 feet bsg <br /> Groundwater gradient in the July 2003 sampling event was reported to be directed to the <br /> southwest at approximately 0 05 foot per foot In the October 2003 sampling event,the <br /> groundwater gradient was reported to be directed to the north, at 0 004 foot per foot It is likely <br /> the groundwater gradient from the July 2003 event was not indicative of true groundwater <br /> gradient, based on comparison to data from surrounding properties and comparison to the <br />'• October 2003 site sampling event, both which suggest regional groundwater gradient is directed <br /> to the north A summary of data for water level measurements and groundwater elevations is <br />' presented in Table 8 A groundwater contour map from the October 2003 sampling event is <br /> included as Figure 7 <br /> rSoil types encountered during tank removal and subsequent investigations consisted of a lean <br /> clay from the ground surface to a maximum explored depth of approximately 23 feet bsg Lean <br /> clays typically have low permeability and high sorption for fuel chemicals The soil types <br /> encountered are consistent with regional soil types, described as a low-permeability grayish <br />' brown and dark grayish brown clay (Capay-Urban land complex, USDA, 1992) Boring logs are <br /> included in Appendix B A cross-section of the site is depicted in Figure 8 <br /> 1 <br /> 6.0 Beneficial Uses of Water <br />' The site is underlain by the Tracy sub-basin of the San Joaquin County groundwater basin, with <br /> an estimated storage capacity of 4 2 million acre-feet(Department of Water Resources [DWR], <br /> 1 <br /> CNCMSHARE%UST0 "0J doc 4 <br /> 1 <br />