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Date January 31,2005 <br /> Quarter 4`h Quarter,2004 <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 /> (SJCEHD) <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 from site wells Site monitoring wells MS-lA, MS- <br /> 1B,MS-2A,MS-2B,MS-3A, and MS-3B were not sampled or monitored this quarter Additionally, VW-6 and <br /> VW-9 were not sampled due to insufficient groundwater <br /> 2 Prepared and submitted quarterly groundwater monitoring report <br /> 3 Continued to inject ambient air at Iow flow rates into well VW-10 <br /> WORK PROPOSED FOR NEXT QUARTER (First 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 (Fourth 2004): <br /> Current Phase of Project Mon iton ng/R emediation _ <br /> Frequency of Groundwater Sampling MW-1 through MW-7, and VW-1 through VW-12, MS-1A, <br /> MS-113, MS-2A, MS-26, MS-3A, and MS-36 sampled <br /> quarterly <br /> Frequency of Groundwater Monitoring Quarterly <br /> Is Free Product (FP) Present onsite No <br /> Current Remediation Techniques Natural attenua_tion/Air bubbling <br /> Approximate Depth to Groundwater _ 43 18 to 45 89 feet below ground surface (jigs) <br /> Groundwater Flow and Gradient Southeast to Southwest @ 0 01 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 result for gasoline range organics (GRO) in sample MW-6 may be biased high due to a <br /> high average percent recovery reported in the associated MS/MSD and LCS analyses <br /> • The reported results for GRO in samples VW-1, VW-3, VW-4, VW-7, VW-11, and VW-12 may be <br /> . biased high due to a high average percent recovery reported in the associated LCS analysis <br /> K.1WprocmO BP ARC0Y121301Quarta1y1200444 QTR 0412130 GANM 4Q04 do Page 1 <br />