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• Date April 25,2002 <br /> Quarter IQ02 <br /> ARCO QUARTERLY GROUNDWATER MONITORING REPORT <br /> Facility No 6020 Address 1711 E Yosemite Ave,Manteca,CA <br /> Environmental Engineer Paul Supple <br /> Consulting Co/Contact Person SECOR/Rusty Benkosky <br /> Consultant Project No 77BP 56020 00 0701 <br /> Primary Agency/Regulatory ID No San Joaquin County Public Health Services(SJCPHS) <br /> Assembly Bill 681 Status Property owned by Atlantic Richfield Company <br /> WORK PERFORMED THIS QUARTER (First Quarter - 2002): <br /> 1 Performed quarterly groundwater monitoring and sampling <br /> 2 Prepared and submitted quarterly groundwater monitoring report <br /> WORK PROPOSED FOR NEXT QUARTER (Second Quarter- 2002): <br /> 1 Perform quarterly groundwater monitoring and sampling <br /> 2 Prepare and submit quarterly groundwater monitoring report <br /> i <br /> QUARTERLY RESULTS SUMMARY <br /> Current Phase of Project Monitoring <br /> Frequency of Groundwater Sampling MW-5 through MW-10 sampled quarterly <br /> Frequency of Groundwater Monitoring Quarterly <br /> Is Free Product(FP)Present Onsite No <br /> Current Remediation Techruques Natural attenuation <br /> Approximate Depth to Groundwater 191/4 to 21 ft <br /> Groundwater Flow and Gradient North-Northwest @ 0 003 ft/ft <br /> DISCUSSION: <br /> Total petroleum hydrocarbons as gasoline(TPHg),benzene,toluene,ethylbenzene,and xylenes(total) were <br /> reported as nondetectable in all six wells sampled this quarter Methyl tert-butyl ether(MtBE),analyzed using <br /> EPA Method 8260B, was reported in one of the six wells(MW-6)at a concentration of 210 ppb Chemical <br /> concentrations were consistent with historical analytical data,excepe for a decrease in MtBE in MW-6 <br /> Groundwater elevations across the site increased by an average of 122 ft Groundwater flow was north-northwest <br /> at an approximate gradient of 0 003 ft/ft <br /> This report presents our understanding of existing conditions at the subject site The conclusions contained herein <br /> are based on the analytical results,and professional judgment in accordance with current standards of professional <br /> practice,no other warranty is expressed or implied SECOR assumes no responsibility for exploratory borings or <br /> data reported by other consultants or contractors <br />