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Date: April 21,2004 <br /> Quarter l"Quarter 2004 <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 OL058 <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 2004): <br /> 1 Performed quarterly groundwater momtonng and sampling <br /> 2 Prepared and submitted quarterly groundwater monitoring report <br /> 3 Performed one additional sampling event of monitoring wells MW-9 and MW-10 due to the detection of ethanol <br /> during the quarterly monitoring event February 16,2004 <br /> 4 Monitoring well MW-9 was redeveloped on March 16,2004,following the cleaning of the well casing <br /> WORK PROPOSED FOR NEXT QUARTER (Second 2004): <br /> 1 Perform quarterly groundwater monitoring and sampling <br /> 2 Prepare and submit quarterly groundwater monitoring report <br /> QUARTERLY RESULTS SUMMARY (First 2004): <br /> Current Phase of Project Monitoring <br /> Frequency of Groundwater Sampling MW-5 through MW-10 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 21 11 to 24 41 feet below ground surface <br /> Groundwater Flow and Gradient Northeast - Northwest 0 0 009---0 016 ft/ft <br /> ANALYTICAL DATA REVIEW: <br /> Please note that during 2003, the laboratory has changed Total Petroleum Hydrocarbons as Gasoline (TPHg) to <br /> Gasoline Range Organics (GRO) The resulting data may be impacted by the potential inclusion of non-TPHg <br /> analytes within the requested carbon range resulting in a higher concentration being reported Where the resulting <br /> GRO concentration is based on a single analyte(i e ,a non-TPHg analyte or a single TPHg analyte), the analyte will <br /> be identified if possible <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 /> KNWpm.oV5 RP ARco`)W2uQuar ,Iyll QTR 0416020GWMR IQ04 do Page 1 <br />