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n�Vy S ECOR <br />,r <br />�a. Date April 8, 2003 <br />Quarter 1 Q03 <br />ARCO QUARTERLY GROUNDWATER MONITORING REPORT <br />Facility No 4932 Address 16 E Harding Way, Stockton, CA <br />ARCO Environmental Engineer Paul Supple <br />Consulting Co /Contact Person SECOR/Rusty Benkosky <br />Consultant Project No 77BP 54932 03 0336 <br />Primary Agency/Regulatory ID No San Joaquin County Public Health Services (SJCPHS) <br />Assembly Bill 681 Status Property owned by ARCO <br />WORK PERFORMED THIS QUARTER (First Quarter - 2003): <br />1 Performed quarterly groundwater monitoring and sampling <br />2 Prepared and submitted quarterly groundwater monitoring report including additional figures <br />3 Initiated construction of soil vapor extraction and groundwater extraction remedial system <br />WORK PROPOSED FOR NEXT QUARTER (Second Quarter - 2003): <br />1 Perform quarterly groundwater monitoring and sampling <br />2 Prepare and submit quarterly groundwater monitoring report including additional figures <br />4 Complete construction and begin operation of soil vapor extraction and groundwater extraction <br />remedial system <br />QUARTERLY RESULTS SUMMARY <br />Current Phase of Project Monitoring/Remediation <br />Frequency of Groundwater MW -1 through MW -11, EW -1, EW -2, EW -6, DMW-1 <br />through DMW-3 and SVE-1 Sampled quarterly <br />Frequency of Groundwater Quarterly <br />Is Free Product (FP) Present Onsite No <br />Current Remediation Techniques Remedial System currently being installed-SVE/GWE <br />Approximate Depth to Groundwater 29 30 — 3120 ft <br />Groundwater Flow and Gradient Shallow - Northeast @ 0 008 ft/ft <br />Deep — Northeast @ 0 005 ft/ft <br />DISCUSSION: <br />Total petroleum hydrocarbons as gasoline (TPHg) were reported in six of the ten wells sampled this quarter <br />at concentrations ranging from 100 ppb (MW -9) to 220,000 ppb (EW -1) Benzene was reported in five of <br />the ten wells at concentrations ranging from 1 5 ppb (MW -9) to 8,000 ppb (EW -1) Methyl tert-butyl ether <br />(MtBE), analyzed using EPA Method 8260B, was reported in eight of the ten wells at concentrations ranging <br />f� from 0 53 ppb (MW -3) to 200,000 ppb (EW -1) 1,2-Dichloroethane (1,2 -DCA) was reported in four of the <br />tt wells at concentrations ranging from 0 55 ppb (MW -7) to 7 6 ppb (MW -5) Tert-butyl alcohol (TBA), tort - <br />amyl methyl ether (TAME), di -isopropyl ether (DIPE), ethylene dibromide (EDB), and ethyl tent butyl ether <br />(ETBE) were not detected this quarter Chemical concentrations were generally consistent with historical <br />11ARC0149321aMRs1200311QMR03 doc .2- <br />