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Date January 31,2006 <br /> Quarter 4'b Quarter 2005 <br /> • ARCO QUARTERLY GROUNDWATER MONITORING REPORT <br /> Facility No 2130 <br /> Address 7906 North EI Dorado Street, Stockton, CA <br /> ARCO Environmental Engineer Paul Supple _ <br /> Consulting Co/Contact Person URS/Vernon Elarth <br /> Consultant Project No 38466468 0A143 <br /> Primary Agency San Joaquin County Environmental Health Division <br /> Assembly Bill 681 Status Property owned by Atlantic Richfield Company _ <br /> WORK PERFORMED THIS QUARTER (Fourth 2005): <br /> 1 Performed quarterly groundwater monitoring and sampling from site wells VW-6 were not sampled due to <br /> insufficient groundwater during this quarterly event <br /> 2 Prepared and submitted quarterly groundwater monitoring report <br /> 3 Continued to infect ambient air at low flow rates into well VW-10 <br /> WORK PROPOSED FOR NEXT QUARTER (First 2006): <br /> 1 Perform quarterly groundwater monitoring and sampling <br /> 2 Prepare and submit quarterly groundwater monitoring report <br /> • 3 Continue bubbling of ambient air at low flow rates into well VW-10 <br /> QUARTERLY RESULTS SUMMARY (Fourth 2005). <br /> Current Phase of Project Monitoring/Remediation <br /> Frequency of Groundwater Sampling MW-1 through MW-7, and VW-1 through VW-12, MS-1 A, <br /> MS-1B, MS-2A, MS-2B, MS-3A, and MS-3B sampled <br /> quarterly <br /> Frequency of Groundwater Monitoring Quarter) <br /> Is Free Product (FP) Present onsite No <br /> Current Remediation Techniques Natural attenuation/Air bubbling <br /> Approximate Depth to Groundwater 42 35 to 44 35 feet below ground surface b s <br /> Groundwater Flow and Gradient Northeast-Northwest @ 0 004 feet/foot (ft/ft) <br /> ANALYTICAL DATA REVIEW: <br /> Based on the review of the analytical and hardcopy data (chain-of-custody records, blanks,dilutions, holding times, <br /> LCS/LCSD results,MS/MSD results,and surrogate recoveries),the data are acceptable as reported by the laboratory <br /> with the following limitations <br /> • The reported results for gasoline range organics in samples MW-1 and MW-6 are due to <br /> chromatographic peaks present in the gasoline quantitation rage, however, the peaks present do not <br /> resemble the pattern for gasoline <br /> • The reported results for ethanol in samples MW-1, MW-2, MW-3, MW-4, MW-5, MW-6, MW-7, <br /> • VW-1, VW-2, VW-3, VW-4, VW-5, MS-2A, MS-2B, MS-3A, and MS-3B should be considered <br /> estimated because the associated continuing calibration standard was outside of acceptance criteria <br /> I <br /> I <br /> K 1WpMLe�sU5 BA ARCOW213UQua crl Q005\4 QTR 05121306WMR 4Q05 Joc Page 1 <br />