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Date: March 29,2005 <br /> Quarter: 15`Quarter,2005 <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: U R S/J eff rey Brooks <br /> Consultant Project No.: 38466523.OA143 <br /> Primary Agency/Regulatory ID No., San Joaquin County Environmental Health Department <br /> Assembly Bill 681 Status: Property owned by Atlantic Richfield Company <br /> WORK PERFORMED THIS QUARTER (First 2005): <br /> 1. Performed quarterly groundwater monitoring and sampling. <br /> 2. Prepared and submitted quarterly groundwater monitoring report. <br /> WORK PROPOSED FOR NEXT QUARTER (Second 2005): <br /> 1. Perform quarterly groundwater monitoring and sampling. <br /> 2. Prepare and submit quarterly groundwater monitoring report. <br /> QUARTERLY RESULTS SUMMARY (First 2005): <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: 8.54—9.23 feet below ground surface b s <br /> Groundwater Flow and Gradient: Northwest @ 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 /> LCM/LCSD results,MS/MSD results,and surrogate recoveries),the data are acceptable as reported by the laboratory <br /> with the following limitation: <br /> • The reported results for gasoline range organics (GRO) in samples MW-2, MW-3, and MW-4 may be <br /> biased low as demonstrated by a low surrogate recoverrdueto matrix interference.�\ <br /> DISCUSSION: v�4 <br /> Methyl tert-butyl ether (MtBE) was the only analyte detected above laboratory reporting limits in the groundwater <br /> sample collected from site monitoring well MW-2 this quarter. The MtBE concentration in MW-2 is consistent with <br /> historical detections at this location.No other analytes were detected above laboratory reporting limits. <br /> Groundwater elevations in site wells increased relative to the previous quarter. The approximate groundwater flow <br /> direction across the site was toward the northwest at an average hydraulic gradient of 0.01 ft/ft. <br /> KAWproce OBPARC0\D54501QuarterlyV005U QTR 45\5450GWMR 1Q05Am Page 1 <br />