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First Quarter 1995 Monitoring and Sampling Report -. April 21,1995 The Southland Corporation,455 Grant Line Rd,,Tracy,CA 2 Separate-phase hydrocarbons were not detected in any of the monitoring wells. The water table elevations, calculated from the March 20, 1995 monitoring data,were used to prepare a potentiometric surface map (Figure 3,Attachment 1). The groundwater flow is toward the north at a hydraulic gradient of approximately 0.01 ft/ft. The historical and current water level measurements are presented in Table 1 (Attachment 2). Monitoring Well Sampling and Analytical Results Groundwater samples were collected from nine site-related monitoring wells (MW-4, 5, 8, 9, 10, 12, 13, 14, and GWE-1). MW-2 was not sampled this quarter because the well casing was clogged with tree bark. Before sampling, at least four well-casing volumes of groundwater was removed from each of the monitoring wells, unless the wells were purged dry. Field measurements of temperature, conductivity, and pH were recorded during well purging. The groundwater samples were collected using a Teflon®sampler and placed in analysis-specific sample containers with analyses-specific preservatives. The samples were then sealed and labeled with the job identification number,the sample number, date,time, and type of laboratory analysis required. The samples were stored on ice in an insulated container and transported under chain-of-custody manifest to GTEL Environmental Laboratories, Inc, in Concord, California. Dissolved hydrocarbons were detected in groundwater samples from monitoring wells MW-8, 9, 10, and the extraction well, GWE-1 (Table 1,Attachment 2). The highest concentrations of benzene and TPH-G were detected in MW-10 at 9,800 parts per billion (ppb) and 47,000 ppb, respectively (Figure 4, Attachment 1). The laboratory analytical reports and the chain-of-custody records for the March 20, 1995 sampling event are included in Attachment 3. Summary During this reporting period, 13 groundwater monitoring wells and 1 groundwater extraction well were monitored on March 20, 1995, for DTW and for the presence of SP hydrocarbons. No SP hydrocarbons were detected in any of the monitoring wells. The potentiometric surface map shows a gradient to the north that has not changed significantly since the previous quarter's monitoring event (Figure 3,Attachment 1). Analytical results indicate that highest benzene and TPH-G concentrations were detected in MWA 0 at 9,800 ppb and 47,000 ppb, respectively. 015MI95.RP7(STHL-5) LEI❑`k GROUNDWATER ❑❑TECHNOLOGY .