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• <br /> INTRODUCTION <br /> This report presents data collected during the fourth quarter 1998 monitoring period at the <br /> USA Gasoline Corporation (USA) Service Station No. 65, located at 2500 West Lodi Avenue, <br /> Lodi, California (see Figure 1). Groundwater monitoring consists of measuring depths to water, <br /> collecting groundwater samples for subjective laboratory analysis, and evaluating gradient and <br /> direction of groundwater flow beneath the site. <br /> 2 BACKGROUND <br /> The subject site is currently an operating retail gasoline station located on West Lodi Avenue in <br /> Lodi, California. During the course of the site assessment programs conducted between 1987 <br /> and 1993, a total of 10 groundwater monitoring wells were installed. Historically, all wells have <br /> shown petroleum hydrocarbon impact, however monitoring wells MW-1 and MW-5 through <br /> MW-7 have had very little impact. <br /> Three gasoline USTs and associated piping were removed and replaced on October 6 and 7, <br /> 1997. Approximately 500 cubic yards of hydrocarbon-impacted soil were excavated and <br /> removed from the site during these activities. <br /> 3 GROUNDWATER GRADIENT AND DIRECTION <br /> 0 <br /> The fourth quarter 1998 groundwater monitoring event at USA Service Station No. 65 was <br /> conducted on December 29, 1998. Depth to groundwater measurements at monitoring wells <br /> MW-1 through MW-8 were made using an electronic sounding device and recorded on <br /> monitoring well data forms (see Appendix A). Locations of monitoring wells are illustrated in <br /> Figure 2. Depth to groundwater measurements are summarized in the table. <br /> At the time of the fourth quarter monitoring event, groundwater was first encountered at depths <br /> of 36.61 to 38.79 feet below ground surface. November 30 depth-to-groundwater measurements <br /> were used in constructing a groundwater contour map (see Figure 2). During the fourth quarter <br /> 1998 monitoring event, groundwater beneath the site generally flowed to the south-southeast <br /> with a gradient of 0.003. Field data sheets are presented in Appendix A. <br /> 4 SAMPLING, ANALYSIS, AND MONITORING PROGRAM <br /> RESULTS <br /> Groundwater samples were collected from seven monitoring wells on December 29, 1998. <br /> Sample locations are illustrated in Figure 2. Monitoring wells MW-2, S-1 and S-2 were not <br /> • sampled during the fourth quarter 1998 sampling event. Monitoring well MW-2 was not located, <br /> and historically, wells S-1 and S-2 have been dry. Samples were analyzed for total petroleum <br /> SACIC:%FILFSIUSA\USA65QR.DOC-981???:4 ;V&"e_& <br /> 1 Rev.D,1/29/99 <br />