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(ik <br /> Date January 30,2002 <br /> • Quarter 4Q01 <br /> FORMER ATLANTIC RICHFIELD COMPANY QUARTERLY GROUNDWATER <br /> MONITORING REPORT <br /> Facility No 4493 Address 205 N Center St , Stockton,CA <br /> Environmental Engineer Paul Supple <br /> Consulting Co/Contact Person SECOR/Rusty Benkosky <br /> Consultant Project No 077 43280 704 <br /> Primary Agency/Regulatory ID No San Joaquin County Environmental Health Department(SJCEHD) <br /> Assembly Bill 681 Status Property owned by City of Stockton <br /> WORK PERFORMED THIS QUARTER (Fourth Quarter - 2001): <br /> 1 Performed quarterly groundwater monitoring and sampling <br /> 2 Prepared and subnutted quarterly groundwater monitoring report <br /> WORK PROPOSED FOR NEXT QUARTER (First Quarter - 2002): <br /> 1 Conduct quarterly groundwater monitoring and sampling <br /> 2 Prepare and submit quarterly groundwater monitoring report <br /> . 3 Install multi-completion wells once construction activities by the City of Stockton are complete <br /> QUARTERLY RESULTS SUMMARY <br /> Current Phase of Project Monitortng/Assessment <br /> Frequency of Groundwater Sampling MW-1 through MW-7 sampled quarterly <br /> Frequency of Groundwater Monitoring Quarterly <br /> Is Free Product(FP)Present Onsite No <br /> Current Remediation Techniques Natural attenuation <br /> Approximate Depth to Groundwater 11 to 17 ft <br /> Groundwater Flow and Gradient Northeast @ 0 015 ft/ft <br /> DISCUSSION: <br /> Total petroleum hydrocarbons as gasoline(TPHg) were reported in four of the seven monitoring wells sampled this <br /> quarter at concentrations ranging from 54 ppb(MW-5)to 1,900 ppb(MW-3) Benzene, analyzed by EPA Method <br /> 826013,was reported in three of the seven wells at concentrations ranging from 5 9 ppb(MW-5)to 39 ppb(MW-3) <br /> Methyl tert-butyl ether(MtBE),analyzed using EPA Method 8260B,was reported in four of the seven wells with <br /> concentrations ranging from 1 6 ppb(MW-2)to 150 ppb(MW-3) Other fuel oxygenates were not detected to the <br /> wells,some volatile orgainic compounds were detected at low concentrations(Table 3) Chemical concentrations <br /> were generally consistent with previous quarterly data with the following exceptions TPHg, benzene,toluene, <br /> ethylbenzene,and xylenes concentrations in well MW-3 increased significantly,TPHg,benzene,ethylbenzene, <br /> xylenes,and MtBE concentrations in well MW-4 decreased significantly, and TPHg, benzene,xylenes,and MtBE <br /> concentrations in well MW-7 increased Groundwater elevations decreased by an average of 0 44 feet Groundwater <br /> flow was to the northeast at an approximate gradient of 0 015 ft/ft <br />