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0 a <br /> • The highest levels reported in the GeoAudrt investigation were from boring GB2, south of the <br /> UST location The groundwater sample was reported to contain 13,000 ppb TPHG, 83 ppb <br /> benzene, 840 ppb toluene, 230 ppb ethylbenzene and 1900 ppb xylenes They also reported 3400 <br /> ppb TPHG, 35 ppb benzene, 48 ppb toluene, 16 ppb ethylbenzene and 96 ppb xylenes in boring <br /> GB8 <br /> Several other groundwater samples from both investigations contained less sigmficant levels of <br /> petroleum compounds Complete groundwater sample results are presented in Table 2 for this <br /> investigation and in Table 4 for the GeoAudrt investigation Groundwater sample results for <br /> TPHG are shown on Figure 4 <br /> 3.3 Site Geology and Hydrogeology <br /> Soils at the site are generally fine to medium grained sands with occasional silty sands First <br /> groundwater was found at approximately 12 5 feet bgs The GeoAudrt investigation reported <br /> groundwater at 15 feet bgs It is believed that the groundwater flow direction at the site is to the <br /> west or northwest <br /> 4.0 CONCLUSIONS AND RECOMMENDATIONS <br /> 4.1 Conclusions <br /> Elevated concentrations of petroleum compounds were found in both the soil and groundwater <br /> The highest concentrations were found in the area around the dispenser islands This could <br /> indicate a release from either the piping or the dispensers <br /> Boring GB8 showed a high level of TPHG in the soil, as well as a significant level in the <br /> groundwater This rmght be related to the former tanks <br /> Boring IW showed a high level of TPHD at a depth of 3 feet Borings B-9 and B-10 showed only <br /> very low levels of petroleum compounds This indicates a small, localized area of contamination <br /> immediately below the diesel dispenser <br /> 4.2 Recommendations <br /> Additional characterization will be required to determine the extent of petroleum impacted soil <br /> and groundwater The groundwater flow direction must also be determined Remedy <br /> recommends that five groundwater monitoring wells be installed on the site Locations of the <br /> proposed wells are shown on Figure 5 <br /> Initial Site Characterization Report April 1997 <br /> 2072 JV Yosemite,Ave,Manteca, CA 3 015 001\P <br />