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1 <br /> t1.0 INTRODUCTION <br /> USA Gasoline Corporation (USA) has retained The Park Corporation (Park) to assist them in the <br /> environmental assessment and remediation at their gasoline station#110, located at 2132 East <br /> Mariposa Road, Stockton, California, as shown on Figures 1, 2 and 3 Mr Snkanth Dasappa of <br /> USA authorized Park to prepare this "First Quarter, 1997, Groundwater Monitoring Report" <br /> (QMR) for the site This report has been prepared for subrmttal to the San Joaquin County Public <br /> Health Services, Environmental Health Division (County), the lead regulatory agency overseeing <br /> environmental issues at the site The County Site Code is #1669 <br /> 1.1 Scope of Work <br /> Groundwater monitoring was completed at the site on January ry24 1997 The following ing is a beef <br /> summary of the scope of work authonzed by USA <br /> • Locate and measure depths to groundwater in wells MW-1-P through MW-6_P, S- <br /> 1, <br /> 1, MW-1, and MW-2, <br /> • Purge a minimum of three equivalent well volumes of groundwater from each of <br /> the wells and monitor pH, temperature and conductivity, <br /> • Collect groundwater samples from the monitoring wells, <br /> • Analyze water samples for total petroleum hydrocarbon in the gasoline range <br /> (TPH G, EPA Method 8015 modified), benzene, toluene, ethylbenzene, and total <br /> 1 xylenes (BTEX, EPA Method 8020), and <br /> • Prepare this QMR for submittal to USA and the County <br /> 2.0 GROUNDWATER MONITORING <br /> 1 The following section discusses field protocol used during data collection for thisQ MR <br /> 2.1 Groundwater Elevations <br /> Upon gauging depths to groundwater, nine groundwater monitoring wells (MW-1, MW-2, S-1, <br /> and MW-I-P through MW-6-P) were checked for the presence of free floating hydrocarbon using <br /> an interface probe, S-1 was dry No free product was present in any of the wells Depths to <br /> groundwater measurements were then taken from each well from surveyed marks on the casing <br /> using an electric water Ievel sensor Calculated groundwater elevations are presented in Table 1 <br /> and shown on Figure 4 Field data sheets are included in Appendix A <br /> r2.2 Monitoring Well Purging <br /> The monitoring wells were purged using a 2-inch diameter, submersible Rediflo groundwater <br /> pump, until a nunimum of three equivalent well volumes of water were removed from each well <br />