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S E C O R <br /> Date October 14, 2004 <br /> Quarter 3Q04 <br /> ARCO QUARTERLY GROUNDWATER MONITORING REPORT <br /> Facility No 595 Address 6100 N Highway 99, Stockton, CA <br /> Environmental Engineer Paul Supple <br /> Consulting Co/Contact Person SECOR/Cltnton Harms <br /> Consultant Project No 77BP 50595 04 0336 <br /> Primary Agency/Regulatory ID No San Joaquin County Public Health Services <br /> SJCPHS <br /> Assembly Bill 681 Status Property owned by Madeline Scannavino <br /> WORK PERFORMED THIS QUARTER (Third Quarter- 2004): <br /> 1 Performed groundwater monitoring and sampling (including onsite water supply well WSW, offsite <br /> water supply well DW-2) <br /> 2 Prepared and submitted July, August, and September monthly system performance summary <br /> 3 Maintained water treatment system at Weinerschnitzei <br /> WORK PROPOSED FOR NEXT QUARTER (Fourth Quarter- 2004): <br /> 1 Perform quarterly groundwater monitoring and sampling (including WSW and DW-2) <br /> 2 Prepare and submit quarterly groundwater monitoring report <br /> 3 Prepare and submit monthly system performance summary for October, November, <br /> and December <br /> 4 Conduct additional site assessment pending receipt of access agreement <br /> QUARTERLY RESULTS SUMMARY <br /> Current Phase of Project Monitoring/Offsite Remediation <br /> Frequency of Groundwater <br /> Sampling MW-1 through MW-10, DMW-1 through DMW-3, WSW, <br /> and DW-2 sampled quarterly <br /> DW-1 influent and effluent sampled monthly <br /> Frequency of Groundwater <br /> Monitoring Quarters <br /> Is Free Product (FP) Present <br /> Onsite No <br /> Current Remediation Techniques Granular activated carbon treatment on off-site well DW-1 <br /> Approximate Depth to <br /> Groundwater 65 98 to 70 69 ft <br /> Shallow Groundwater Northwest @ 0 011 ft/ft and a local cone of depression toward <br /> Flow/Gradient MW-7 and MW-4 0 006 ft/ft, 0 003 ft/ft, and 0 016 ft/ft <br /> Deep Groundwater Flow/Gradient Northwest 0 0 003 ft/ft <br /> DISCUSSION. <br /> Total petroleum hydrocarbons as gasoline (TPHg) were reported in one of the eleven monitoring wells <br /> sampled this quarter at a concentration of 1,900 parts per billion (MW-1) Benzene was reported in three <br /> of the eleven monitoring wells sampled at concentrations of 0 53 ppb (MW-3) to 570 ppb (MW-1) Methyl <br /> tert-butyl ether (MtBE), analyzed using EPA Method 82606, was detected in seven of the eleven wells <br /> sampled at concentrations ranging from, 2 6 ppb (MW-3) to 86 ppb (DMW-3) 1,2-dichloroethane (1,2- <br /> -'"1', <br /> 11ARC0105951QMRs120M3QMR04 doc v�V <br />