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THIRD QUARTER,1998 GROUNDWATER MONITORING REPORT . USA STATION#65-LODI AUGUST, 1998 GHH representatives provided product line and UST excavation soil sampling services to USA during the retrofit activities, as directed by the County. Soil sampling activities and analytical results are presented in the "Soil Excavation and Product Line Sampling" letter report to the County dated October 22, 1997. Monitoring well S-1 was damaged and repaired during the field activities. 3.0 SCOPE OF WORK The following is a brief summary of the scope of work performed by GHH during the groundwater monitoring commencing on July 29, 1998. • Locate and measure depths to groundwater in monitoring wells MW-1 through MW-8, S- 1 and S-2. • Purge a minimum of three equivalent well volumes of groundwater from each of the sampled wells, while monitoring pH, temperature and conductivity. • Collect groundwater samples from the purged monitoring wells. . • Analyze water samples for TPH in the gasoline range (TPH G), benzene, toluene, ethylbenzene and xylene (BTEX) and methyl-tert-butyl-ether(MTBE) using EPA Methods 8015 Modified and 8020, respectively. • Prepare this QMR for submittal to USA and the County. 4.4 GROUNDWATER MONITORING The following section discusses field protocol used during data collection for this QMR. 4.1 Groundwater Elevations Prior to gauging depths to groundwater, the monitoring wells were checked for the presence of free product-using an interface probe. -Depths to groundwater measurements were thea taken from each well from surveyed marks on the casing using an electric water level sensor. Groundwater elevation data are summarized in Table 1, and 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. 3