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i <br /> i <br /> j • Laboratory analysis detected fecal coliform in nine of the wells. <br /> See Table 1 for a summary of results. <br /> CONCLUSIONS <br /> • The decrease of ground water elevations by an average 115 feet since the last <br /> quarterly monitoring event,likely the result of seasonal lack of precipitation, may <br /> be contributing to retardation of offsite movement of the dissolved-phase <br /> hydrocarbon plume. <br /> a The lateral extent of the dissolved-phase benzene plume is assessed in the vicinity <br /> of Monitoring Wells MW-1, MW-8, MW-9, and MW-10. All of these onsite wells <br /> are in the vicinity or downgradient from the former USTs. <br /> ll <br /> • The decrease m TPH-G and benzene m ground water samples collected from <br /> MW-1 and MW-10 may indicate decreased dissolved-phase migration. <br /> • Fecal coliform (E.C.) detected in monitoring wells south of the onsite 7-11 <br /> building are likely a result of a leaking onsite sewer lateral. <br /> CURRENT ACTIVITIES <br /> • The San Joaquin County Public Health Services letter dated June 12, 1992, <br /> addresses the presence of dissolved-phase hydrocarbons in five Monitoring Wells <br /> MW-1, MW-5, MW-8, MW-9, and MW-10. The letter recommends remediation <br /> be initiated soon to prevent the plume from migrating offsite. Alton Geoscience <br /> is currently pursuing a remediation plan to address regulatory concerns and has <br /> initiated quarterly fluid-level monitoring and ground water sampling June 1992. <br /> ALTON GEOSCIENCE <br /> GY,. aCY <br /> Tion D. Grotts <br /> Project ager, <br /> -Peter q. e, RG. 5 <br /> i <br /> Associat orthern California Operations <br /> 3 <br />