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Date- October 27,2004 <br /> Quarter 34 Quarter,2004 <br /> i <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 OL058 <br /> Primary Agency San Joaquin County Environmental Health Division <br /> (SJCEHD) <br /> Assembly Bill 681 Status _Property owned by Atlantic Richfield Company <br /> WORK PERFORMED THIS QUARTER (Third 2004): <br /> 1 Performed quarterly groundwater monitoring and sampling from site wells <br /> 2 Prepared and submitted quarterly groundwater monitoring report <br /> I <br /> 3 Continued to infect ambient air at Iow flow rates into well VW-10 <br /> WORK PROPOSED FOR NEXT QUARTER (Fourth 2004): <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-l0 <br /> 4 Complete required well vault repairs <br /> QUARTERLY RESULTS SUMMARY (Third 2004): <br /> Current Phase of Project Monitoring/Remediation <br /> Frequency of Groundwater Sampling MW-1 through MW-7, and VW-1 through VW-12, MS-1A, <br /> MS-1 B, MS-2A, MS-2B, MS-3A, and MS-3B sampled <br /> quarterly <br /> Frequency of Groundwater Monitoring Quarterly <br /> Is Free Product (FP) Present onsite No <br /> Current Remediation Techniques Natural attenuation/Air bubbling <br /> Approximate Depth to Groundwater 47 38 to 49 60 feet below ground surface (bgs) <br /> Groundwater Flow and Gradient Northeast @ 0 002 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 benzene and toluene in sample MS-IB, tert-butyl alcohol (TBA) and 1,2- <br /> dichloroethane (1,2-DCA) in sample MW-3, and for gasoline range organics (GRO) in samples VW-1 <br /> and VW-8 may be biased high as demonstrated by a high surrogate recovery due to matrix interference <br /> . • The reported result for toluene in sample MS-3A may be biased high due to a high average percent <br /> recovery reported in the associated LCS analysis <br /> K_1Wpr c ssVS RP ARC0\02130\Quaner1y W4\3 QTR 0412130 GWW 3"doc Page 1 <br />