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�i Ss <br /> Date January 18,2001 <br /> Quarter 4Q00 <br /> ARCO QUARTERLY GROUNDWATER MONITORING REPORT <br /> Facility No 595 Address 6100 North Highway 99,Stockton,CA <br /> ARCO Environmental Engineer Paul Supple <br /> Consulting Co/Contact Person SECOR International Incorporated/Rusty Benkosky <br /> Consultant Protect No 077 42007 704 <br /> Primary Agency/Regulatory ID No San Joaquin County Environmental Health Services <br /> Assembly Bill 681 Status Property is owned by Madeline Scannavino <br /> i <br /> WORK PERFORMED THIS QUARTER (Fourth Quarter—2000): <br /> 1 Conducted groundwater monitoring and sampling(including onsite water supply well) <br /> 2 Prepared and submitted quarterly groundwater monitoring report <br /> WORK PROPOSED FOR NEXT QUARTER (First Quarter—2001): <br /> 1 Conduct quarterly groundwater monitoring and sampling <br /> 2 Prepare and submit quarterly groundwater monitoring report <br /> 3 Perform door-to-door sensitive receptor survey <br /> 4 Perform additional site assessment as proposed in SECOR's Work Plan for Additional Sate Assessment dated <br /> November 30, 2000 <br /> QUARTERLY RESULTS SUMMARY <br /> Current Phase of Project Monitoring <br /> Frequency of Groundwater Sampling Wells MW-1,MW-2,MW-3,MW-4,and WSW-I sampled <br /> Frequency of Groundwater Monitoring uarterl <br /> Is Free Product(FP)Present On-Site No <br /> FP Recovered this Quarter NA <br /> Cumulative FP Recovered to Date NA <br /> Current Remediation Techniques Natural Attenuation <br /> Approximate Depth to Groundwater 58 5 to 60 5 ft <br /> Groundwater Gradient Variable N-S at 0 011 to 0 026 ft/ft <br /> DISCUSSION: <br /> TPHg was reported in all four wells sampled this quarter at concentrations ranging from 162 ppb (MW-3) to 9,230 <br /> ppb(MW-4) Benzene was reported in three of the four wells sampled this quarter at concentrations ranging from <br /> 12 6 ppb(MW-2) to 1,740 ppb(MW-4) MtBE (by EPA Method 8260) was detected in all four wells sampled at <br /> concentrations ranging from 2 5 ppb (MW-1) to 2,200 ppb(MW-4) Tert-butyl alcohol (TBA) was reported in two <br /> wells at concentrations of 62 ppb(MW-2)and 570 ppb (MW-4) 1,2-Dichloroethane(1,2-DCA) was reported in <br /> two of the four wells sampled at concentrations of 38 ppb (MW-3)and 280 ppb(MW-4) Additionally,the onsite <br />