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c7eoCogicaC �"ec�i�ics W. <br /> 1101 7`h Street <br /> Modesto,California 95354 <br /> (209)522-4119/Fax(209)522-4227 <br /> ' Report <br /> Site Conceptual Model <br /> (June 2006 Revision) <br /> ' Valentine (Castle Motors) <br /> 2315 N. El Dorado St. <br /> Stockton, CA <br /> Project No 723 2 <br /> June 16, 2006 <br /> 1 <br /> M1.0 INTRODUCTION <br /> In April 1987 the site's two 3,000-gallon gasoline underground storage tanks (UST) and one <br /> ' 150-gallon waste oil UST were removed (see Figure 1 Area Map & Figure 2 Site Map) <br /> Analyses of soil samples from the UST excavations revealed that a petroleum hydrocarbon <br /> release had occurred The San Joaquin County Environmental Health Division (SJC/EHD) <br /> ' subsequently directed Mr Valentine to begin an investigation to determine the extent of the <br /> petroleum release <br /> ' The following is a summary of work performed at the site to date <br /> • In October 1993 four boreholes (SB-1 thru SB-4) were placed around the location of the <br /> former waste oil tank Results showed that all soil samples, except for the 36-foot sample <br /> ' from SB-2, were below detection limits for BTEX and TPH-G <br /> • In September 1994 monitoring well MW-1 was installed at the site Soil sample <br /> ' analytical results indicated the presence of BTEX and TPH-G in the soil to a depth of 56 <br /> feet bgs Waste oil was detected in the shallow soil samples <br /> • In June 1995 two additional monitoring wells, MW-2 & MW-3, were installed at the site <br /> ' Results showed the presence of high levels of BTEX and TPH-G in the soil and <br /> groundwater <br /> • In June 1996 three additional monitoring wells (MW-4, MW-5 & MW-6) and soil boring <br /> ' "SB-B" were installed at the site Soil sample analytical results indicated the presence of <br /> significant levels of BTEX and TPH-G The results also indicated that the pump-island <br /> • was a mayor source of contamination <br />