ARCHIVED REPORTS_XR0002223 - Laserfiche WebLink

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• 2 . 0 GROUNDWATER FLOW DIRECTION AND GRADIENT On January 26, 2006, 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 As requested by the San Joaquin County PHS-EHD, the groundwater sampling was 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 Groundwater elevation data from the three sites are presented in Tables One, Two, and Three Groundwater elevation data for the former BP service station was not available at the time of report generation A groundwater potentiometric surface map that includes available groundwater elevation data from the monitoring wells in the area i s presented as Figure 2 The groundwater flow direction on the site is t o the north-northwest with a gradient of approximately 0 0054 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 headspace, labeled and placed in a cooler with wet ice for transport to Kiff Analytical, LLC of Davis, California (ELAP #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, a n d total xylenes (collectively known as BTEX), and fuel oxygenates by EPA Singh's Unocal Service Station Quarterly Report — January 2006 Sampling -2-