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Date January 22,2003 <br /> Quarter 41° Quarter,2002 <br /> ARCO QUARTERLY GROUNDWATER MONITORING REPORT <br /> Facility No 2168 <br /> Address 411 Charter Way, Stockton, CA <br /> ARCO Environmental Engineer Kyle Christie <br /> Consulting Co/Contact Person URSI Vernon Elarth <br /> Consultant Project No 38465939 00436 <br /> Primary Regulatory Agency San Joaquin County Public Health Services <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 Sampling MW-1, MW-1 A, MW-4A, MW-5, MW-7, MW-8, MW-8A, <br /> MW-8D, MW-12 through MW-18, AND MW-21 through <br /> MW-25 Sampled Quarterly <br /> Frequency of Groundwater Monitoring Quarterly <br /> Is Free Product (FP) Present on Site No <br /> Current Remediation Techniques Natural attenuation <br /> Approximate Depth to Groundwater 22 23 to 24 42 ft <br /> Groundwater Flow and Gradient Northeast to southeast @ 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 linuts were due to dilutions performed by the laboratory in order to quantitate a target <br /> analyte,and <br /> • All analytes analyzed by Method 8260E COC requests analysis by 8015,8021 and 8260 <br /> DISCUSSION: <br /> Analytes detected in site monitoring wells this quarter included total petroleum hydrocarbons as gasoline (TPHg), <br /> benzene, toluene, ethylbenzene, total xylenes (BTEX), methyl tert-butyl ether(MtBE), and 1,2-dichloroethane(1,2- <br /> DCA) Analyte concentrations were generally consistent with historic data with the exception of well MW-4, where <br /> the benzene concentration was at a new high (15,000 rmcrograms per liter) relative to historic data, and well MW-5 <br /> where TPHg and BTEX concentrations were at new lows relative to historic concentrations Groundwater elevations <br /> K U5 BP ARCUD2 S681QuarterlyW_Q7A 02M68 GWMR4Q02 do Page 1 <br />