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Date: October 27,2005 <br /> Quarter: 3' Quarter,2005 <br /> ARCO QUARTERLY GROUNDWATER MONITORING REPORT <br /> Facility No: 2130 <br /> Address: 7906 North EI Dorado Street, Stockton, CA <br /> ARCO Environmental Engineer: Paul Supple <br /> Consulting Co./Contact Person: URS/Vernon Elarth <br /> Consultant Project No: 38466468.OA143 <br /> Primary Agency: _San Joaquin County Environmental Health Division <br /> Assembly Bill 681 Status: Property owned by Atlantic Richfield Company <br /> WORK PERFORMED THIS QUARTER (Third 2005): <br /> 1. Performed quarterly groundwater monitoring and sampling from site wells. VW-6 and VW-9 were not sampled <br /> due to insufficient groundwater during this quarterly event. <br /> 2. Prepared and submitted quarterly groundwater monitoring report. <br /> 3. Continued to inject ambient air at low flow rates into well VW-10. <br /> WORK PROPOSED FOR NEXT QUARTER (Fourth 2005): <br /> 1. Perform quarterly groundwater monitoring and sampling. <br /> 2. Prepare and submit quarterly groundwater monitoring report. <br /> 3. Continue bubbling of ambient air at low flow rates into well VW-10. <br /> QUARTERLY RESULTS SUMMARY (Third 2005): <br /> Current Phase of Project: Monitoring/Remediation <br /> Frequency of Groundwater Sampling: MW-1 through MW-7, and VW-1 through VW-12, MS-1 A, <br /> MS-1 B, MS-2A, MS-213, MS-3A, and MS-3B sampled <br /> quarterly <br /> Frequency of Groundwater Monitoring: Quarters <br /> Is Free Product (FP) Present onsite: No <br /> Current Remediation Techniques: _ Natural attenuation/Air bubbling <br /> Approximate Depth to Groundwater: 45.18 to 47.05 feet below ground surface (b9s) <br /> Groundwater Flow and Gradient: East-Southeast @ 0.005 feet/foot 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 /> • The reported results for gasoline range organics (GRO) in samples MW-6, VW-4, MS-1A,and MS-1B <br /> are due to chromatographic peaks present in the gasoline quantitation range,however,the peaks present <br /> do not resemble the pattern for gasoline. <br /> • The reported results for benzene, toluene, ethylbenzene, total xylenes (BTEX), oxygenates, GRO, and <br /> 1,2-dichlorothane (1,2-DCA) in samples MS-3A and MS-3B may be biased low since the analyses for <br /> these analytes were performed two days beyond the U.S.EPA recommended holding time of 14 days. <br /> K:1Wpro vssV5 SP ARCOM130\Qaa eriy12005\3 QTR 0512130 GWMR 3WA. Page 1 <br />