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2 .0 GROUNDWATER FLOW DIRECTION AND GRADIENT On August 12, 2005, ASE measured the depth to water in the six site groundwater monitoring wells using an electric water level sounder. The surface of the groundwater was also checked for the presence of free- floating hydrocarbons or sheen. No free-floating hydrocarbons or sheen were observed in any of the site groundwater monitoring wells Although requested by the San Joaquin County PHS-EHD, the groundwater sampling could not be coordinated with the consultants investigating two adjacent properties, the former BP Service Station located at 2375 Tracy Boulevard to the west and the former Chevron Station located at 575 Grant Line Road to the north, due to scheduling conflicts, those site were sampled on July 29, 2005 Groundwater elevation data from the three sites are presented in Tables One, Two, and Three. A groundwater potentiometric surface map that includes groundwater elevation data from all of the monitoring wells in the area is presented as Figure 2. The groundwater flow direction is to the north-northwest with a gradient of approximately 0 0079 ft/ft This gradient and flow direction are consistent with previous findings. • 3 0 GROUNDWATER SAMPLE COLLECTION AND ANALYSIS Prior to sampling, each well to be sampled was purged of three well casing volumes of groundwater using disposable polyethylene bailers All six monitoring wells were sampled this quarter Petroleum hydrocarbon odors were noted during the purging and sampling of monitoring wells MW-1, MW-2, and MW-5 The parameters pH, temperature, -and conductivity were monitored during the well purging, and samples were not collected until these parameters stabilized. Groundwater samples were collected from each well using the same disposable polyethylene bailers and were decanted from the bottom of the bailers using low-flow emptying devices into 40-m1 volatile organic analysis (VOA) vials, pre- preserved with hydrochloric acid The samples were capped without x headspace, labeled and placed in a cooler with wet ice for transport to Kiff Analytical, LLC of Davis, California (FLAP #2236) under appropriate chain-of-custody documentation Well sampling field logs are presented in Appendix A The groundwater samples were analyzed for total petroleum hydrocarbons as gasoline (TPH-G), benzene, toluene, ethyl benzene, and total xylenes (collectively known as BTEX), and fuel oxygenates by EPA Method 8260 Analytical data from the three sites are presented as Tables Singh's Unocal Service Station Quarterly Report - August 2005 Sampling -2-