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Date December 10, 1999 <br /> Quarter 3Q99 <br /> ARCO QUARTERLY GROUNDWATER MONITORING REPORT <br /> Facility No 2133 Address 2908 Benjamin Holt Drive, Stockton, CA <br /> ARCO Environmental Engineer Paul Supple <br /> Consulting Co/Contact Person SECOR International Incorporated/Rusty Benkosky <br /> Consultant Project No 077 41727 006 <br /> Primary Agency/Regulatory ID No San Joaquin County Environmental Health <br /> Assembly Bill 681 Status Property Owned by ARCO Products Company <br /> WORK PERFORMED THIS QUARTER (Third Quarter- 1999): <br /> 1 Prepared and submitted second quarter 1999 groundwater monitoring report <br /> 2 Performed third quarter groundwater monitoring event <br /> 3 Performed operation and maintenance on remediation system <br /> WORK PROPOSED FOR NEXT QUARTER (Fourth Quarter— 1999): <br /> 1 Prepare and submit third quarter 1999 groundwater monitoring report <br /> 2 Perform fourth quarter 1999 groundwater monitoring event <br /> 3 --Perform operation and maintenance on remediation system <br /> QUARTERLY RESULTS SUMMARY <br /> Current Phase of Project Remediation and Monitoring <br /> Frequency of Groundwater Sampling E-2 E-8 through E-12 PR71 BDH-I MW-4 MW-5 <br /> (quarterly)-E-3 through E-7 PR-2 BDH-2. <br /> _MW-1,MW-2.MW-3 (1"and 3rd quarter) <br /> Frequency of Groundwater Monitoring Qorterly <br /> Is Free Product(FP)Present On-Site No <br /> Cumulative FP Recovered to Date 642 pounds <br /> Cumulative TPH-g removed by GWETS 3,980 unds <br /> Total groundwater extracted 32,000,000 gallons <br /> Current Remediation Techniques SVE/AS SVE down due to high G <br /> TPH-g removed by SVET flus quarter 0 <br /> Cumulative TPH-g removed by SVES 4,815 pgunds <br /> Approximate Depth to Groundwater 9 12 to 1194 <br /> Groundwater Gradient North-northeast A 0 001 ft/ t <br /> DISCUSSION: <br /> TPH-g was detected in four of the nineteen wells sampled this quarter at concentrations ranging from 107 ppb(E- <br /> 4)to 481 ppb(E-3) Benzene was reported in three wells at a maximum concentration of 9 31 ppb(E-10) MtBE <br />•� was detected in five wells at concentrations ranging from 8 53 ppb(E4)to 4,800 ppb(MW-1) This is the first <br /> time MtBE has been reported in well MW-1 since 1996 Groundwater elevations across the site decreased by an <br /> average of 162 feet this quarter Groundwater flow was primarily to north-northeast generally consistent with <br /> historical data Well MW-5 was inaccessible due to constructions activities associated with the offramp west of <br />