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Date: April 21,2004 <br /> Quarter: J."Quarter,2004 <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 (First 2004): <br /> 1. Performed quarterly groundwater monitoring and sampling. <br /> 2. Prepared and submitted quarterly groundwater monitoring report. <br /> WORK PROPOSED FOR NEXT QUARTER (Second 2004): <br /> 1. Perform quarterly groundwater monitoring and sampling. <br /> 2. Prepare and submit quarterly groundwater monitoring report. <br /> QUARTERLY RESULTS SUMMARY (First 2004): <br /> iCurrent 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: 9.45—10.62 feet below ground surface - <br /> Groundwater Flow and Gradient: Northwest @ 0.02 ft/ft <br /> ANALYTICAL DATA REVIEW: <br /> Please note that during 2003, the laboratory has changed Total Petroleum Hydrocarbons as Gasoline (TPHg) to <br /> Gasoline Range Organics (GRO). The resulting data may be impacted by the potential inclusion of non-TPHg <br /> analytes within the requested carbon range resulting in a higher concentration being reported. Where the resulting <br /> GRO concentration is based on a single analyte(i.e., a non-TPHg analyte or a single TPHg analyte), the analyte will <br /> be identified if possible. <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 <br /> laboratory. <br /> DISCUSSION: <br /> Gasoline range organics (GRO), benzene, toluene, ethylbenzene, and total xylenes (BTEX) were reported as below <br /> laboratory detection limits in all groundwater samples collected from site wells this quarter. Methyl tert-butyl ether <br /> (MtBE)was detected in MW-2 at 19 micrograms per liter(pg/L),a decrease in concentration relative to the previous <br /> monitoring event. MEBE was reported as below method detection limits in well MW-4 for the first time since <br /> K-1WprocessV5 BP A1tC01054501Quarier1y11 QTR 0415450 GWMR 1Q04.&c Page 1 <br />