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Date February 6,2003 <br /> Quarter: 4's Quarter,2002 <br /> • 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 38466092 00436 <br /> Primary Agency/Regulatory ID No San Joaquin County Public Health Services SJCPHS <br /> Assembly Bill 681 Status Property owned by Atlantic Richfield Company <br /> WORK PERFORMED THIS QUARTER (Fourth 2002): <br /> 1 Performed quarterly groundwater monitoring and sampling <br /> 2 Prepared and submitted quarterly groundwater monitoring report <br /> WORK PROPOSED FOR NEXT QUARTER (First 2003): <br /> 1 Perform quarterly groundwater monitoring and sampling <br /> 2 Prepare and submit quarterly groundwater monitoring report <br /> QUARTERLY RESULTS SUMMARY (Fourth 2002) <br /> Current Phase of Project Monitoring <br /> Frequency of Groundwater MW-5 through MW-10 sampled quarterly <br /> Sampling <br /> Frequency of Groundwater Quarterly <br /> Is Free Product (FP) Present Onsite No <br /> Current Remediation Techniques Natural attenuation <br /> Approximate Depth to Groundwater 20 24 to 21 95 feet below ground surface <br /> Groundwater Flow and Gradient North-Northwest @ 0 002 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 /> • Elevated reporting limits were due to dilutions performed by the laboratory in order to quantitate a <br /> target analyte <br /> • The data for MW-6 are estimated due to analysis done 16 days beyond holding time <br /> • The results for MtBE in MW-7,MW-&,MW-9 and MW-10 may be biased high due to continuing <br /> calibration verification(CCV)falling outside acceptance criteria <br /> • The data for TBA and MtBE for sample MW-5 may be biased low due to CCV falling outside <br /> acceptance criteria <br /> K LF5 BA ARC01060201Quwier1y44_QTR 0216020 GWMR4Q02 Jac Page 1 <br />