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i <br /> ® I ENVIRONMENTAL TECHNOLOGIES CORPORATION r+ <br /> February 13, 1996 <br /> 94-326 - - <br /> Ms Mary Meays <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br /> P O Box 388 <br /> Stockton, CA 95201-0388 <br /> Subject Groundwater Monitoring Report, October through December 1995, 26080 Thornton <br /> Road, Thornton, CA, Site Code 1864 <br /> Ms Meays <br /> This letter report summarizes groundwater monitoring activities conducted by Smith Environmental <br /> Technologies Corporation at the subject site (Figure 1) <br /> BACKGROUND <br /> On September 6, 1989, three underground gasoline storage tanks were removed at the project site by <br /> Western Meter Service of Stockton, California Soil samples were collected beneath each tank and the <br /> associated piping Soil samples collected from beneath two of the tanks contained moderate to high <br /> levels of ethylbenzene and xylenes (l 2 to 70 parts per million [ppm]) as well as total petroleum <br /> hydrocarbons as gasoline (TPHg), at 470-830 ppm <br /> Due to the presence of elevated concentrations of petroleum hydrocarbons in the tank pit soil samples, <br /> further investigation was required by San Joaquin County Public Health Services, Environmental <br /> Health Division (PHS/EHD) <br /> 4 <br /> In a two-phased approach beginning on November 1, 1990, RESNA personnel advanced six soil <br /> borings (MW1-MW6) to depths ranging from 27 to 30 feet below grade at the project site to <br /> accomplish the following 1) define the lateral and vertical extent of hydrocarbon Impacted soils, 2) <br /> determine soil stratigraphy, and 3) install groundwater monitoring wells within the uppermost aquifer <br /> in order to assess groundwater quality The boring/well locations are plotted on Figure 2 Field <br /> methodology and analytical results are discussed in detail in RESNA's Intenm Problem Assessment <br /> Report, dated January 13, 1992 <br /> The site's station building and garage were demolished in December 1994, in part to facilitate the <br /> removal of hydrocarbon contaminated soil which is suspected beneath the station building The <br /> • demolition of the station building was requested in PHS/EHD correspondence dated July 7, 1994 A <br /> w 1943261QUARTLYI4QR-1995 DOC I <br /> 1260 Graphics Drive Modesto,CA 95351-1502 (209)579-2221 Fax(209)579-2225 <br /> Engineering Consulting Remediation Construction <br />