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' SECOND QUARTER,1997 GROUNDWATER MONITORING REPORT USA STATION#65-LODI ' JUNE,1997 3.0 SCOPE OF WORK Groundwater monitoring was completed at the site on April 14, 1997 The following is a beef ' summary of the scope of work authorized by USA ® Locate and measure depths to groundwater in monitoring wells MW-1 through IMW-8, S-1 and S-2, Purge a minimum of three equivalent well volumes of groundwater from each of the sampled wells, monitor pH, temperature and conductivity, • Collect groundwater samples from the purged monitoring wells, 0 Analyze water samples for TPH in the gasoline range (TPH G), methyl-tert-butyl- ether(MTBE) and BTEX, using EPA Methods 8015 Modified and 8020, respectively, and D Prepare this QMR for submittal to USA and the County 4.0 GROUNDWATER MONITORING The following section discusses field protocol used during data collection for thisQ MR 4.1 Groundwater Elevations Upon gauging depths to groundwater, the groundwater monitoring wells were checked for the ' presence of free floating hydrocarbon using an interface probe Depths to groundwater measurements were then taken from each well from surveyed marks on the casing using an ' electric water level sensor or interface probe Calculated groundwater elevations are presented in Table 1 The field data sheets are included in Appendix A 4.2 Monitoring Well Purging The monitoring wells were purged using a 2-inch diameter submersible Grundfos groundwater ' pump or disposable bailer, until a minimum of three equivalent well volumes of water were removed from each well Groundwater purged from the wells was placed into Department of Transportation (DOT) approved 55-gallon drums and stored on-site prior to disposal by USA To reduce the potential for cross-contamination between wells, all purging and sampling p g equipment was washed in a trisodium phosphate solution and rinsed in potable water prior to each usage 3 j