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k � <br /> ' r�1 emcon <br /> 1433 North Market Boulevard • Sacramento Calif&ja 9 $ e TV16)928-3300• Fox(916)928-3341 <br /> `7 39 April 4, 1995 <br /> Project 0805-114 03 <br /> Mr Kyle Christie <br /> ARCO Products Company J <br /> 2155 South Bascom, Suite 202 ��,�,(�5 f v�e! <br /> Campbell, California 95008 !"" <br /> Re Fourth Quarter 1994 Status Report for ARCO Products Company (ARCO) Service Station <br /> No 2130, 7906 North El Dorado Street, Stockton, California <br /> Dear Mr Christie <br /> At the request of ARCO, EMCON has conducted an environmental investigation and is currently <br /> operating a remedial system at the subject site (see Figure 1) This status report includes information <br /> for fourth quarter 1994 on subjective analysis of water samples from each monitoring well, the <br /> thickness of floating product in the monitoring wells, measurements of groundwater elevations in each <br /> monitoring well., evaluation of the groundwater gradient, collecting and analyzing groundwater <br /> samples, and performance data for an air sparge remediation system <br /> 1 <br /> BACKGROUND <br /> Environmental work performed at the site has included drilling 20 soil borings on site and 5 borings off <br /> site Ten vapor extraction wells (VW-1 through VW-10) were drilled on site Five on-site groundwater <br /> monitoring wells were drilled (MW-1 through MW-5) and five off-site monitoring wells were drilled <br /> (MW-6 through MW-10) One air sparge well (AS-1) and three air sparge monitoring points (MS-1 <br /> through MS-3) were drilled on site During construction of well MW-9, cement slurry was accidentally <br /> introduced into the slotted screen, and therefore, the well was destroyed and another boring was drilled <br /> near well MW-9 and converted to a monitoring well (MW-10) Well locations are shown on Figure 2 <br /> Residual hydrocarbons were detected m soil to 60 feet below grade at the groundwater interface near <br /> the existing tanks, however, gasoline hydrocarbons were not detected in the off-site soil borings <br /> Dissolved hydrocarbons were detected at concentrations above maxunum contaminant levels (MCLS) <br /> in the five on-site and in two off-site groundwater monitoring wells, but concentrations of dissolved <br /> hydrocarbons did not exceed MCLS in samples from wells MW-8 and MW-10 <br /> During October 1993, RESNA Industries (RESNA) of Rancho Cordova, California, observed <br /> Triangle, Inc, (Triangle) of Sacramento, California, excavate trenches and install horizontal piping for <br /> use during site remediation <br /> 5AC/N WJ"805\08051140 3AM-95\MAM 1 <br />