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7 <br /> Date: January 15,2004 <br /> Quarter: 4`h Quarter,2003 <br /> I <br /> • ARCO QUARTERLY GROUNDWATER MONITORING REPORT <br /> Facility No.: 5450 <br /> Address: 1617 West Fremont Street, Stockton, CA <br /> ARCO Environmental Engineer: Paul Supple <br /> Consulting Co./Contact Person: URSNernon Elarth <br /> Consultant Project No.: 38466523.01_058 <br /> Primary Agency/Regulatory ID No.: San Joaquin County Environmental Health Dept. SJCEHD <br /> Assembly Bill 681 Status: Property owned by Atlantic Richfield Company <br /> WORK PERFORMED THIS QUARTER (Fourth 2003): <br /> 1. Performed quarterly groundwater monitoring and sampling. <br /> 2. Prepared and submitted quarterly groundwater monitoring report. <br /> WORK PROPOSED FOR NEXT QUARTER (First 2004): <br /> 1. Perform quarterly groundwater monitoring and sampling. <br /> 2. Prepare and submit quarterly groundwater monitoring report. <br /> QUARTERLY RESULTS SUMMARY (Fourth 2003): <br /> • Current Phase of Project: Monitoring <br /> Frequency of Groundwater Sampling: MW-2 through MW-4 sampled quarterly <br /> Frequency of Groundwater Monitoring: Quarterly <br /> Is Free Product (FP) Present Onsite: No <br /> Current Remediation Techniques: Natural attenuation <br /> Approximate Depth to Groundwater: _11.46— 11.68 feet below ground surface <br /> Groundwater Flow and Gradient: North-Northwest @ 0.004 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 elevated reporting limits were the result of dilutions performed by the laboratory in order to quantitate a <br /> target analyte(s). <br /> DISCUSSION: <br /> Total petroleum hydrocarbons as gasoline (TPHg), benzene, toluene, ethylbenzene, and total xylenes (BTEX) were <br /> reported as below laboratory detection limits in all groundwater samples collected from site wells this quarter. <br /> Methyl tert-butyl ether (MtBE) was detected in MW-2 and MW-4 at concentrations of 36 and 1.4 micrograms per <br /> liter (pg/L), respectively. An increase in MtBE concentration for MW-2 relative to the previous quarter. No other <br /> analytes were detected above method detection limits. Groundwater elevations in site wells increased relative to the <br /> previous quarter. The approximate groundwater flow direction was to the north-northwest at an average gradient of <br /> . 0.004 ft/ft. <br /> KAWproc mO BP ARCM545MQua erlyw QTR 03 5450 GWMR 4Q03.doc Page 1 <br />