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r , <br /> c <br /> 711 <br /> July 10, 1997 <br /> Ms. Mary Meays <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br /> P O Box 388 <br /> Stockton, California 95201-0388 <br /> RE: Preliminary Site Closure Summary <br /> C M Weber Enterprises Property <br /> Former Shell Service Station <br /> 141 North El Dorado Street <br /> Stockton, California <br /> WIC #204-7524-1509 <br /> Dear Ms Meays <br /> During a meeting on May 20, 1997, San Joaquin County Public Health Services <br /> (SJCPHS) requested a site summary document to evaluate whether site closure was <br /> warranted at the referenced site (Plates 1 and 2) This Preliminary Site Closure Summary <br /> presents a review of remedial efforts at the site, recent ground water monitoring results, <br /> and possible sources of chlorinated solvent detected at site <br /> Sr.e Remediation Sumnmory <br /> A ground water extraction (GWE) system was in operation at the site from March 2, 1993 <br /> through September 5, 1995 Several soil vapor extraction (SVE) systems have operated at <br /> the site The most recent soil vapor extraction system operation utilizing activated carbon <br /> was terminated on August 21, 1996 The following table summarizes remediation <br /> performed to date <br /> Total Purgeable Petroleum Hydrocarbons Removed (pounds) <br /> LIQUID PHASE VAPOR PHASE CUMULATIVE <br /> 37 3277 3314 <br /> In April 1996, eight soil borings were drilled to evaluate the effectiveness of SVE at the <br /> site Total Purgeable Petroleum Hydrocarbons quantified as gasoline (TPPH) were not <br /> detected (ND) in 25 of the 29 soil samples submitted for chemical analysis TPPH <br /> concentrations in the four remaining soil samples were 14, 6 9, 34, and 970 ppm <br /> Benzene, toluene, ethylbenzene, and xylenes (BTEX) were ND in 28 of the 29 soil <br /> samples submitted for chemical analysis Benzene was detected in one soil sample at a <br /> concentration of 0 010 ppm Soil chemical data are summarized in Table 1 and on Plate 2 <br /> TPPH concentrations in ground water decreased from a maximum concentration of 47,000 <br /> ppb in May 1993 to ND in October 1995 in Well MW-3 Benzene concentrations in Well <br /> MW-3 decreased from a maximum concentration of 2,600 ppb in February 1994 to ND in <br /> October 1995 Similar trends in ground water petroleum hydrocarbon concentrations were <br /> observed in the other site wells Ground water chemical data are summarized in Table 2 <br /> Cnviros, Inc 270 Perkins Street Sonoma California Tel 707/935 4850 <br /> P 0 Bax 259 95476 0259 Fax 707 935 6649 <br />