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5i <br /> Date December 5,2001 <br /> Quarter 3Q01 <br /> • <br /> FORMER ARCO QUARTERLY GROUNDWATER MONITORING REPORT <br /> Facility No 4493 Address 205 N Center St,Stockton,CA <br /> ARCO Environmental Engineer Paul Supple _ <br /> Consulting Co/Contact Person SECOR/Rusty Benkosky — <br /> Consultant Project No 077 43280 703 <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 (Third Quarter - 2001): <br /> 1 Performed quarterly groundwater monitoring and sampling <br /> 2 Prepared and submitted quarterly groundwater monitoring report <br /> WORK PROPOSED FOR NEXT QUARTER (Fourth Quarter- 2001): <br /> 1 Conduct quarterly groundwater monitoring and sampling <br /> 2 Prepare and submit quarterly groundwater monitoring report <br /> 3 Perform additional site assessment pending the approval of encroachment permits from the City of Stockton <br /> QUARTERLY RESULTS SUMMARY <br /> Current Phase of Protect Monitoring/Assessment <br /> Frequency of Groundwater Sampling _MW-1 through MW-7 sampled quarterly T� <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 113/4-16 ft <br /> Groundwater Flow and Gradient Northeast @ 0 008 ft/ft <br /> DISCUSSION: <br /> Total petroleum hydrocarbons as gasoline(TPHg)were reported in three of the six monitoring wells sampled this <br /> quarter at concentrations ranging from 100 ppb (MW-2) to 1,600 ppb(MW-4) Benzene was reported in three of the <br /> six wells at concentrations ranging from 2 5 ppb(MW-1)to 110 ppb(MW-4) Methyl tert-butyl ether(MtBE), <br /> analyzed using EPA Method 8260B,was reported in one of the six wells at a concentration of 680 ppb(MW-4) <br /> Chemical concentrations were generally consitent with previous data with the exception of well MW-4,which <br /> showed a decrease in TPHg,and MW-6,which showed a decrease in MtBE Groundwater flow was to the northeast <br /> at an approximate gradient of 0 008 ft/ft SECOR was unable to access well MW-3 due to construction activities at <br /> the site <br /> • <br />