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1117 Lone Palm Suite B <br /> Modesto California 95351 <br /> 7VA LTC wwwatc enviro com <br /> 2095792221 <br /> Fax 209 579 2225 <br /> A S S O C I A T E S I N C <br /> }�'1 <br /> February 27, 7'02 <br /> 54 62582 000: <br /> Mr Harlin Kn-)11 <br /> San Joaquin County <br /> Environmental Health Dcpartment <br /> 304 E Weber Ave , Third Floor <br /> Stockton, CA 95202 <br /> Subject First Quarter 2002 Groundwater Monitoring Report for 26056126080 Thornton <br /> Road, f hornton, CA, Site Code 1864 <br /> Dear Mr Kncll <br /> This report prevents the results of quarterly groundwater monitoring and sampling performed on <br /> January 15, 20G2 by ATC Associates Inc at the site located at 26080 Thornton Rd Thornton, <br /> California (Figure 1) Monitoring was performed to determine the groundwater flow direction <br /> and the hydravl.c gradient in the aquifer Sampling was performed to monitor the distribution of <br /> petroleum hym oc,arbons in groundwater at the site <br /> BACKGROUI TD <br /> On September 6, 1989, Western Meter Service of Stockton, California removed three <br /> underground gazolme storage tanks at the project site Soil samples were collected beneath each <br /> tank and the associated piping Soil samples collected from beneath two of the tanks contained <br /> moderate to high levels of ethylbenzene and xylenes (1 2 to 70 parts per million [ppm]) as well <br /> as total petroleum hydrocarbons as gasoline (TPHg) at 470 to 830 ppm <br /> Due to the pr,;,ence of e:,at.ed conce^ti attons of petroleu.lr hydrocarbons in the tangy. pit soil <br /> samples, fur,. .:r investigattorp was required by San Joaquin County Public Health Services, <br /> Environment:.' Health Division (PHS/EHD) <br /> In a two-phases approach beginning on November 1, 1990, RESNA Industries Inc personnel <br /> advanced six s,,a borings (MW1 through MW6) to depths ranging from 27 to 30 feet below <br /> grade at the projezt site to accomplish the following 1) define the lateral and vertical extent of <br /> hydrocarbon inij,,-"-ed soils, 2) determine soil stratigraphy, and 3) install groundwater <br /> monitoring wCa-, within the uppermost aquifer in order to assess groundwater quality The <br /> boring/well to nuns are plotted on Figure 2 Field methodology and analytical results are <br />\ discussed in L _.;.: "-ESNA's Interim Problem Assessment Report, dated January 13, 1992 <br /> w 1Wordpro1625'�21Quartly11QR-2002 doc 1 <br />