Laserfiche WebLink
t <br /> i Date December 23,2004 <br /> Quarter 4`h 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 (Fourth 2004): <br /> 1 Performed quarterly groundwater monitoring and sampling <br /> 2 Prepared and submitted quarterly groundwater monitoring report <br /> WORK PROPOSED FOR NEXT QUARTER (First 2005): <br /> 1 Perform quarterly groundwater monitoring and sampling <br /> 2 Prepare and subnut quarterly groundwater monitoring report <br /> QUARTERLY RESULTS SUMMARY (Fourth 2004): <br /> Current Phase of Project Monitoring <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 21 40 to 24 08 feet below ground surface b s <br /> Groundwater Flow and Gradient Northwest to Northeast @ 0 004 feet/foot (ft/tt) <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 result for gasoline range organics(GRO) in sample MW-13D may be biased low as <br /> demonstrated by a low surrogate recovery due to matrix interference <br /> • The reported results for methyl tert-butyl ether(MtBE)in samples MW-6 and MW-13D may be biased <br /> high as demonstrated by a high surrogate recovery due to matrix interference <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 In MW-6, MtBE concentrations decreased to the lowest level <br /> reported historically MtBE concentrations in MW-13D were consistent with the previous quarter No other analytes <br /> were detected above laboratory reporting limits in groundwater samples collected from site monitoring wells this <br /> . quarter <br /> K 1Wprocc5W5 BP ARC01060201Quaneriy1200414 QTR 0416020 GWMR 4Q04&c Page 1 <br />