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, ME <br /> _� <br /> f <br /> F <br /> become dry. Seasonal groundwater maps produced ty the San Joaquin County <br /> Department of Public Works suggest that this is due to an annual 10-foot <br /> fluctuation of the water table. <br /> 1.3 HY690CAPSON nISTRIBUTIOH <br /> _ Hydro4arbo�ys have bNen determined present in both unsaturated soil and <br /> groundwater at the site. This determination is based on •=or data elements: <br /> Soil vapor survey. <br /> • Soil sample from 20 feet during the drilling of <br /> monitoring well MW-3. <br /> _ Groundwater samples from wells MW-? and MW-3. <br /> • Soil samples taken from the gasoline UST and pipe excavations. <br /> The soil vapor (1989) survey found greatest hydrocarbon concentrations near <br /> the pump islands and along the Pershing Avenue driveways (Appenaix A). During <br /> well drilling (1990), only soils in NW <br /> -3 contained confirmed hydrocarbons <br /> - (benzene and ethylbenzene were detected at 820 and 43 ppb respectively, TAH_G <br /> was not detected). <br /> Groundwater samples taken from wells 14W-1 and MW-3 had 140 <br /> and 200 ppb TPH-G and 1 and 33 ppb benzene respectively !MW-3 also had 2 and <br /> 1.5 ppb of ethylbenzene and toluene, respectively. Samples collected from MW_ <br /> 4, adjacent to the used oil tank, showed no detectable concentrations of TPH <br /> as diesel (TPH-0), oil and grease (503-E), halocarbons (8010/601) and Cd, Cr, <br /> Pb and Zn. The only detections in water samples from this well were <br /> chloroform 0.9 ` <br /> ( ppb) and zinc (0.02 ppm). A copy of the site assessment <br /> completed in June 1990 is included in Appendix A. <br /> Soil samples taken during UST and piping removal confirmed that hydrocarbo'.is: t1. <br /> (gasoline) are widespread in the gasoline UST and piping areas and confirmed <br /> that minimal or absent hydrocarbons (diesel and oils) are in the motor and <br /> used oil UST area. Soil samples from the gasoline UST area had TPH-G levels <br /> ranging from non-detectable to 3,500 ppm, Only one of eight samples from the <br /> used and motor oil areas contained organic compounds (29 ppm of TAH-0, similar <br /> but not identical to diesel fuel). Analytical results <br /> _Of all_soi_l_-samples--are-- --- ----- ------- <br /> --- ------ --- -----Presented-inTable....1--with-Tatioratory results and chain of custody farms — <br /> contained in Appendix C. <br /> 2 <br /> ,1A:ENG:9205/031291 . <br />