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Date: September 18,2000 <br /> • Quarter: 2Q00 <br /> ARCO QUARTERLY GROUNDWATER MONITORING REPORT <br /> Facility No.: 4493 Address: 205 North Center Street, Stockton,CA <br /> ARCO Environmental Engineer: Chuck Carmel <br /> Consulting Co./Contact Person: SECOR International Incorporated/Rusty Benkosky <br /> Consultant Project No.: 077.41907.702 <br /> Primary Agency/Regulatory ID No.: San Joaquin County Environmental Health Department <br /> Assembly Bill 681 Status: Property Owned by City of Stockton <br /> WORK PERFORMED THIS QUARTER (Second Quarter—2000): <br /> 1. Conducted quarterly groundwater monitoring and sampling. <br /> 2. Prepared and submitted quarterly groundwater monitoring report. <br /> 3. Installed three groundwater monitoring wells and advanced one soil boring for vertical definition. <br /> WORK PROPOSED FOR NEXT QUARTER (Third Quarter—2000): <br /> 1. Conduct quarterly groundwater monitoring and sampling. <br /> 2. Prepare and submit quarterly groundwater monitoring report. <br /> 3. Prepare and submit site assessment report. <br /> QUARTERLY RESULTS SUMMARY <br /> Current Phase of Project: Monitoring/Assessment <br /> Frequency of Groundwater Sampling: MW-1 through MW-7 are 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: 11.63 to 13.81 <br /> Groundwater Gradient: Southeast @ 0.006 <br /> DISCUSSION: <br /> TPHg was reported in one groundwater monitoring well sampled this quarter(MW-4)at a concentration of 2,860 ppb. <br /> Benzene was reported in four of the seven wells sampled this quarter at concentrations ranging from 0.692 ppb(MW-1) <br /> to 186 ppb(MW-4). MtBE was reported in four wells sampled this quarter at concentrations ranging from 20.6 ppb <br /> (MW-1)to 3,790 ppb(MW-4). Trichloroethene(TCE)was reported in 3 of the seven wells sampled this quarter at <br /> concentrations of 77.6 ppb(MW-2), 153 ppb(MW-1),and 156 ppb(MW4). Cis-1,2-Dichloroethene was reported in <br /> five of the seven wells sampled at concentrations ranging from 4.62(MW-2)to 369 ppb(MW-1). Groundwater <br /> elevations across the site increased by an average of.40 feet this quarter and flow was to the southeast with a hydraulic <br /> gradient of approximately 0.006 ft/ft, <br />