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1 <br /> 2.0 GROUNDWATER FLOW DIRECTION AND GRADIENT <br /> ' On April 29, 2005, ASE measured the depth to water in the six site <br /> groundwater monitoring wells using an electric water level sounder. The <br /> 1 surface of the groundwater was also checked for the presence of free- <br /> floating hydrocarbons or sheen. No free-floating hydrocarbons or sheen <br /> were observed in any of the site groundwater monitoring wells. As <br /> requested by the San Joaquin County PHS-EHD, the groundwater sampling <br /> was coordinated with the consultants investigating two adjacent <br /> properties, the former BP Service Station located at 2375 Tracy Boulevard <br /> ' to the west and the former Chevron Station located at 575 Grant Lune <br /> Road to the north. Groundwater elevation data from the three sites are <br /> presented in Tables One, Two, and Three. <br /> A groundwater potentiometric surface map that includes groundwater <br /> 1 elevation data from all of the monitoring wells in the area is presented as <br /> Figure 2. The groundwater flow direction is to the northwest with a <br /> gradient of approximately 0.0071 ft/ft. This gradient and flow direction <br /> ' are consistent with previous findings. <br /> 3 .0 GROUNDWATER SAMPLE COLLECTION AND ANALYSIS <br /> li <br /> Prior to sampling, each well to be sampled was purged of three well casing <br /> ' volumes of groundwater using disposable polyethylene bailers. <br /> Monitoring wells MW-3 and MW-6 were not sampled this quarter. <br /> Petroleum hydrocarbon odors were noted during the purging and <br /> ' sampling of monitoring wells MW-1, MW-2, MW-4 and MW-5 The <br /> parameters pH, temperature, and conductivity were monitored during the <br /> well purging, and samples were not collected until these parameters <br /> ' stabilized. Groundwater samples were collected from each well using the <br /> same disposable polyethylene bailers and were decanted from the bottom <br /> ' of the bailers using low-flow emptying devices into 40-m1 volatile organic <br /> analysis (VOA) vials, pre-preserved with hydrochloric acid. The samples <br /> were capped without headspace, labeled and placed in a cooler with wet <br /> ' ice for transport to Kiff Analytical, LLC of Davis, California (EI-AP #2236) <br /> under appropriate chain-of-custody documentation. Well sampling field <br /> logs are presented in Appendix A. <br /> The groundwater samples were analyzed for total petroleum <br /> hydrocarbons as gasoline (TPH-G), benzene, toluene, ethyl benzene, and <br /> total xylenes (collectively known as BTEX), and fuel oxygenates by EPA <br /> . Method 8260. Analytical data from the three sites are presented as Tables <br /> ' Four, Five, and Six. The certified analytical report and chain-of-custody <br /> Singh's Unocal Service Station Quarterly Report - April 2005 Sampling <br />