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Date: December 16,2002 <br /> Quarter 3rd Quarter,2002 <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 38465927 00336 <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 2002): <br /> 1 Performed quarterly groundwater monitoring and sampling from MW-1 through MW-7 MW-10 is still paved <br /> over <br /> 2 Prepared and submitted quarterly groundwater monitoring report <br /> 3 Continued to inject ambient air at low concentrations <br /> WORK PROPOSED FOR NEXT QUARTER (Fourth 2002). <br /> I <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 selected wells <br /> 4 Efforts will be made to reconstruct the wellhead of MW-10 <br /> 5 Sampling will include the vapor extraction wells at the site,following redevelopment in December <br /> QUARTERLY RESULTS SUMMARY (Third 2002): <br /> Current Phase of Project Mon itonn /Remediation <br /> Frequency of Groundwater Sampling MW-1 through MW-7 sampled 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 43 3 to 45 4 ft <br /> Groundwater Flow and Gradient Northeast @ 0 001 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 /> • <br /> In the total petroleum hydrocarbons as gasoline (TPHg)/benzene, toluene, ethylbenzene, total xylenes <br /> (BTEX) analysis of sample MW-5 the surrogate was outside recovery limits due to matrix interference <br /> The results for TPHg/BTEX in this sample should be considered estimated <br /> r� <br /> K 45 RP ARC0=WQun Icrlyl3_QTR 02\2130GWMR3Q02 d— Page 1 <br />