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J Date January 10,2006 <br /> Quarter 0 Quarter 2005 <br /> •1 ARCO QUARTERLY GROUNDWATER MONITORING REPORT <br /> Facility No 6020 <br /> Address 1711 E Yosemite Ave , Manteca, CA <br /> ARCO Environmental Engineer Paul Supple <br /> Consulting Co/Contact Person URSNernon Elarth <br /> Consultant Project No 38466530 0A143 <br /> Primary Agency/Regulatory ID No San Joaquin County Environmental Health Department <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 <br /> 2 Prepared and submitted quarterly groundwater monitoring report <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 /> QUARTERLY RESULTS SUMMARY (Fourth 2005): <br /> • Current Phase of Project _ Monitoring <br /> Frequency of Groundwater Sampling MW-5 through MW-12, and MW-13D sampledquarterly__ <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 19 39 to 21 55 feet below ground surface (bos) <br /> Groundwater Flow and Gradient North-Northwest @ 0 001 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 ethanol in samples MW-5, MW-6, MW-7, MW-8, MW-9, MW-10, and MW-11 <br /> should be considered estimated because the associated continuing calibration standard was outside of <br /> acceptance criteria <br /> DISCUSSION <br /> MtBE was the only analyte detected above laboratory reporting limits in groundwater samples collected from site <br /> monitoring wells MW-6 and MW-13D this quarter Concentrations of MtBE concentrations in MW-6 decreased to <br /> the lowest level reported historically MW-13D was generally consistent with the previous quarters No other <br /> analytes were detected above laboratory reporting limits in groundwater samples collected from site monitoring wells <br /> this quarter <br /> K 1WprocescV5 BP ARCO\0602MQ>merlyl2005VA QTR 05 6020 GWMR 4Q05 dna Page 1 <br />