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Date January 16,2006 <br /> Quarter 1 s'Quarter 2006 <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 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 (First 2006): <br /> 1 Performed quarterly groundwater monitoring and sampling A complete EPA 8260B list was analyzed by the <br /> laboratory <br /> 2 Prepared and submitted quarterly groundwater monitoring report <br /> 3 Prepared and submitted Site Closure Report <br /> WORK PROPOSED FOR NEXT QUARTER (Second 2006): <br /> 1 Perform quarterly groundwater monitoring and sampling <br /> 2 Prepare and submit quarterly groundwater monitoring report <br /> . 3 if closure is granted,a workplan will be prepared for the destruction of the monitoring wells <br /> QUARTERLY RESULTS SUMMARY (First 2006): <br /> Current Phase of Project Monitoring/Closure <br /> Frequency of Groundwater Sampling MW-5 through MW-12, and MW-13D sampled quarterly <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 18 00 to 20 27 feet below ground surface (bgs) <br /> Groundwater Flow and Gradient North @ 0 003 feet/toot 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/1.CSD 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, MW-11, MW- <br /> 12, and MW-13D should be considered estimated because the associated continuing calibration standard <br /> was outside of acceptance criteria <br /> DISCUSSION <br /> MtBE was the only analyte detected above laboratory reporting limits in groundwater samples collected from site <br /> monitoring well MW-13D this quarter In MW-6, MtBE was not detected for the first time historically MW-13D <br /> • <br /> KIWproc.s\I5BPARCOs0602MQ..mrly4200M1QTR 06KA20GWMRIQp6d— Page 1 <br />