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Date July 16,2001 <br /> Quarter 2Q01 <br /> ARCO QUARTERLY GROUNDWATER MONITORING REPORT <br /> Facility No 6020 Address 1711 E Yosemite Ave,Manteca,CA <br /> ARCO Environmental Engineer Paul Supple <br /> Consulting Co/Contact Person SECOR International Incorporated/Rusty Benkosky <br /> Consultant Project No 077 43345 702 <br /> Primary Agency/Regulatory ID No San Joaquin County Environmental Health Services <br /> Assembly Bill 681 Status Property owned by Atlantic Richfield Company <br /> WORK PERFORMED THIS QUARTER (Second Quarter—2001): <br /> 1 Conducted quarterly groundwater monitoring and sampling <br /> 2 Prepared and submitted quarterly groundwater monitoring report <br /> WORK PROPOSED FOR NEXT QUARTER (Third Quarter - 2001): <br /> 1 Conduct quarterly groundwater monitoring and sampling <br /> 2 Prepare and submit quarterly groundwater monitoring report <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 On-Site No <br /> Current Remediation Techniques Natural attenuation <br /> Approximate Depth to Groundwater 19'x4-21%ft <br /> Groundwater Gradient North @ 0 003 <br /> DISCUSSION: <br /> Total petroleum hydrocarbons as gasoline(TPHg),benzene,toluene,ethylbenzene,and xylenes(total)were <br /> reported below detectable concentrations in the six wells sampled Methyl tert-butyl ether(MtBE)analyzed using <br /> EPA Method 8260A was reported in MW-6 at a concentration of 2,900 ppb Tert-amyl methyl ether(TAME)was <br /> reported in MW-6 at a concentration of 7 1 ppb Groundwater analytical data was relatively consistent with last <br /> quarter's groundwater analytical data Groundwater elevations across the site decreased by an average of 0 36 ft <br /> Groundwater flow was to the north at an approximate gradient of 0 003 <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 />