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Date April 24,2003 <br /> Quarter 1s1 Quarter,2003 <br /> ARCO QUARTERLY GROUNDWATER MONITORING REPORT <br /> Facility No 2168 <br /> Address 411 Charter Way, Stockton, CA <br /> ARCO Environmental Engineer Kyle Christie <br /> Consulting Co/Contact Person URS/Vernon Elarth <br /> Consultant Project No 38466079 00436 <br /> Primary Regulatory Agency San Joaquin Counly Public Health Services <br /> WORK PERFORMED THIS QUARTER (First 2003): <br /> 1 Performed quarterly groundwater monitoring and sampling <br /> 2 Prepared and submitted quarterly groundwater monitoring report <br /> WORK PROPOSED FOR NEXT QUARTER (Second 2003): <br /> 1 Perform quarterly groundwater monitoring and sampling <br /> 2 Prepare and submit quarterly groundwater monitoring report <br /> QUARTERLY RESULTS SUMMARY (First 2002); <br /> • Current Phase of Project Monitoring <br /> Frequency of Groundwater Sampling MW-1, MW-1A, MW-4, MW-5, MW-7, MW-8, MW-SB, <br /> MW-8C Sampled Quarter) <br /> Frequency of Groundwater Monitoring Quarterly <br /> Is Free Product (FP) Present on Site No <br /> Current Remediation Techniques Natural attenuation <br /> Approximate Depth to Groundwater 22 48 to 26 01 <br /> Groundwater Flow and Gradient Northeast to Southeast @ 0 0018 to 0 0027 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/I.CSD results, MS/MSD results, and surrogate recoveries),the data are acceptable as reported by the laboratory <br /> with the following hnutations <br /> • The reported results for toluene in sample MW-8C may be biased low due to a low average percent recovery <br /> reported in the associated MS/MSD analysis <br /> • The elevated reporting limits were due to dilutions performed by the laboratory In order to quantitate a target <br /> analyte <br /> DISCUSSION: <br /> Analytes detected In site monitoring wells this quarter included total petroleum hydrocarbons as gasoline (TPHg), <br /> benzene, toluene, ethylbenzene, total xylenes (BTEX), methyl tert-butyl ether (MtBE), and 1,2-dichloroethane (1,2- <br /> DCA) Analyte concentrations were generally consistent with historic data Groundwater elevations in the site wells <br /> generally decreased relative to the previous quarter The inferred direction of groundwater flow and average <br /> hydraulic gradient were consistent with previous monitoring events <br /> K V5 BP ARco1ml6s1Quarteriyll QTR 0312166 GWMR IQ03 doc Page 1 <br />