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t• <br /> Date January 25,2001 <br /> Quarter 4Q00 <br /> ARCO QUARTERLY GROUNDWATER MONITORING REPORT <br /> Facility No 4932 Address 16 East Harding Way,Stockton, CA <br /> ARCO Environmental Engineer Paul Supple <br /> Consulting Co/Contact Person SECOR International Incorporated/Rusty Benkosky <br /> Consultant Project No 077 42010 704 <br /> Primary Agency/Regulatory ID No San Joaquin County Environmental Health Services <br /> Assembly BiIt 681 Status Property Owned by Atlantic Richfield Company <br /> WORK PERFORMED THIS QUARTER (Fourth Quarter—2000): <br /> 1 Conducted quarterly groundwater monitoring and sampling <br /> 2 Prepared and submitted quarterly groundwater monitoring report <br /> 3 Prepared and submitted,"Workplan for Additional Site Assesment and Interim Remediation/Feastbility <br /> Testing"(SECOR,January 25,200 1) <br /> WORK PROPOSED FOR NEXT QUARTER (First Quarter—2001): <br /> 1 Conduct quarterly groundwater monitoring and sampling <br /> 2 Prepare and submit quarterly groundwater monitonng report <br /> + 3 Perform additional site assesment and interim remediation/fesability testing <br /> QUARTERLY RESULTS SUMMARY <br /> Current Phase of Protect Monitoring/Interim Remediation <br /> Frequency of Groundwater Sampling MW-1 through MW4 and SVE-1 are sampled quarterly <br /> Frequency of Groundwater Monitonng Quarterly <br /> Is Free Product(FP)Present On-Site No <br /> Current Remediation Techniques Natural Attenuation <br /> Approximate Depth to Groundwater 27 to 28°is feet <br /> Groundwater Gradient East-Northeast @ 0 013 ft/ft <br /> DISCUSSION: <br /> TPHg was reported in all of the five groundwater monitonng wells sampled this quarter at concentrations ranging from <br /> 116 ppb(MW-3)to 180,000 ppb(MW-4) Benzene was reported in all five of the wells sampled this quarter at <br /> concentrations ranging from 6 55 ppb(MW-3)to 9,400 ppb(MW-4) MtBE(EPA Method 8260B)was reported in <br /> every well sampled this quarter at concentrations ranging from 2 9 ppb(MW-3)to 350,000 ppb(MW4) Tert-butyl <br /> alcohol(TBA) was not reported in any of the five wells sampled this quarter Tert-amyl methyl ether(TAME)was <br /> reported in one of the five wells at a concentration of 15 ppb(MW-1) 1,2-Dichloroethane(1,2-DCA)was reported in <br /> well MW-1 at a concentration of 35 ppb Groundwater flow was to the east-northeast with a hydraulic gradient of <br /> approximately 0 013 ft/ft <br />