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r <br /> Date: August 19, 1999 <br /> • Quarter: 2Q99 <br /> ARCO QUARTERLY GROUNDWATER MONITORING REPORT <br /> Facility No.: 4493 Address: 205 North Center Street, Stockton, CA <br /> ARCO Environmental Engineer: Paul Supple <br /> Consulting Co./Contact Person: SECOR International Incorporated/Rusty Benkosky <br /> Consultant Project No.: 077.41819.001 <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— 1999): <br /> 1. Performed second quarter groundwater monitoring event. <br /> 2. Repaired well boxes damaged during UST removal activities. <br /> WORK PROPOSED FOR NEXT QUARTER (Third Quarter- 1999): <br /> 1. Prepare and submit second quarter 1999 groundwater monitoring report. <br /> 2. Perform third quarter groundwater monitoring event. <br /> • QUARTERLY RESULTS SUMMARY <br /> Current Phase of Project: Monitoring/Assessment <br /> Frequency of Groundwater Sampling: MW-1 through MW-4 are sampled quarteLly, <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: 11.89 to 12.97 <br /> Groundwater Gradient: Southeast&0.005 fttft <br /> DISCUSSION: <br /> TPH-g was reported in one of the four wells sampled this quarter at a concentration of 10,800 ppb(N fW-4). <br /> Benzene was reported in two wells sampled this quarter at concentrations of 230 ppb(MW-4)and 3.52 ppb <br /> (MW-1). MtBE was reported in two wells at concentrations of 144 ppb(MW-3),and 766 ppb(MW-4). TCE was <br /> detected in two wells at concentrations of 126 ppb(MW-1) and 59.2 ppb (MW-2). PCE was detected in well <br /> MW-lat a concentration of 2.34 ppb. Groundwater flow was to the southeast with a hydraulic gradient of <br /> 0.005 ft/ft. <br />