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GEOLOGICAL AUDIT SERVICES, INC. <br /> SECOND QUARTER 1993 PROJECT STATUS SUMMARY <br />' SITE: ARCO MINI MART <br /> ADDRESS: 4511 Pacific Ave. Stockton, CA <br />' CLIENT: Arthur Wyatt TELEPHONE: 951-1207 <br /> LEAD AGENCY: SAN JOAQUIN COUNTY PHS/EHD <br /> AGENCY CONTACT: Diane Hinson TELEPHONE: 468-3452 <br />' SUMMARY OF WORK COMPLETED <br /> Monitoring wells MW-1 through MW-3 were purged of between 9 and 15 <br />' gallons of water using a Grundfos submersible pump, after the depth <br /> to standing water was measured in each well (Attachment A) . Water <br /> samples were then collected in disposable bailers. <br />' LABORATORY ANALYTICAL RESULTS <br /> BTE&X in MW-1, MW-2 , MW-3 , TPH-G in MW-1 and MW-3 ; no TPH-O in MW3 . <br /> See Table 1 and Attachment B. <br /> GROUNDWATER DEPTH AND GRADIENT <br /> Monitoring Date: 13 May 1993 <br /> Depth Measurements: See Table 2 <br /> Average Depth: 51. 6 feet <br />' Gradient: . 019 ft/ft to N50°W <br /> CONCLUSIONS AND RECOMMENDATIONS <br />' Concentrations of most contaminants have decreased since the <br /> January 1993 monitoring event. This may be due to natural <br />' degradation or to dilution by rising groundwater levels following <br /> spring rains. <br /> The calculated groundwater gradient is nearly identical to that <br />' reported in GeoAudit's First Quarter 1993 Quarterly Status Summary. <br /> This confirms that the local gradient at this site is contrary to <br /> previous assumptions. The northwest gradient and the absence of <br /> TPH-g in MW-2 suggest that the plume of contaminated groundwater <br /> Probably does not extend beneath Pacific Avenue. <br />' In contrast to the January sampling event, motor oil was not <br /> detected in the sample from MW-3 . It is unlikely that the gasoline <br /> detected in MW-3 is due to the February 1991 pipeline leak, because <br /> this well is located up-gradient from the leak. Furthermore, <br /> because no TPH-g was detected in MW-2 , which is on strike with MW- <br /> 3 , the gasoline In MW-3 probably forms a small plume that is <br /> separate from that detected in MW-1 . <br /> We recommend removal and disposal of the barrels of soil and <br /> groundwater that are stored on site. GeoAudit will seek a water <br /> discharge permit from the City of Stockton. <br /> L <br />