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' SUBSURFACE Som AND GROUNDWATER ASSESSMENT REPORT <br /> water supplies The identified municipal and UOP water wells utilize groundwater from the <br /> lower source aquifer Given the underlying geology and hydrogeologic conditions discussed in <br /> the previous sections,the low MTBE concentrations are not expected to represent a threat to <br /> public water supplies, and no water bodies have been identified within the immediate site <br /> vicinity <br /> 1 RECOMMENDATIONS <br /> Considering the minimal impact of MTBE to soil and groundwater, it is ESA's opinion that the <br /> ' conditions at the site are not significantly impacting soil and groundwater, and therefore no <br /> further investigative or remedial action regarding this case is recommended This <br /> recommendation is based on the conclusions, as summarized below, that have been developed <br /> from the findings of the UST removal in April 2000 and the recent subsurface assessment and <br /> water well search performed by ESA <br /> • No TPHG or BTEX were detected in soil or groundwater samples obtained during the recent <br /> subsurface assessment Soils beneath the former UST were not found to be saturated with <br /> petroleum nor were they found to present a significant source for further migration or <br /> ' significant impact to groundwater <br /> • The occurrence of MTBE is localized at low concentrations within the soils immediately <br /> beneath the north and south ends of the former UST excavation and does not represent a <br /> significant mass capable of migrating vertically downward through the soil <br /> • MTBE does not appear to have migrated laterally beyond the areas of soil impact <br /> • The geology and hydrogeology does not appear conducive to initiating future migration of <br /> MTBE from the former UST excavation <br /> • Public groundwater sources identified in the well search are located at substantial distances <br /> both laterally and vertically from the former UST location and possible migration of the <br /> detected MTBE to those sources is considered not likely <br /> Subsurface Soil and Groundwater Assessment FSA/200252 <br /> ' 1081 w Mendocino Avenue Stockton California 1 August 25 2000 <br />