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Mr. Bob Vasquez 2 The Southland Corporation, 455 Grant Line Rd., Tracy, CA November 30, 1994 GROUNDWATER MONITORING DATA Groundwater monitoring was performed on September 27, 1994. Prior to monitoring, the well caps of each well were opened to allow the water level in each well to stabilize to atmospheric pressure. The DTW was measured to the nearest 0.01 foot from the top of the well casing using an ORS Environmental Equipment INTERFACE PROBE Well Monitoring System. Separate-phase hydrocarbons were not detected in any of the monitoring wells. The water-table elevations calculated from the September 27, 1994 monitoring data were used to prepare a potentiometric surface map (Figure 3). No significant change in the potentiometric surface elevation has occurred since the previous quarter's monitoring event. The groundwater flow is toward the northeast at a hydraulic gradient of approximately 0.008 foot/foot. 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 ten site-related monitoring wells (MW-1, 3 through 6, 8 through 11, and 15). MW-2 and extraction well GWE-1 were not sampled this quarter because the MW-2 well casing was clogged with tree bark, and the GWE-1 well cap was stuck tight. Before sampling, at least four well-casing volumes of groundwater was removed from each of the i monitoring wells, unless the wells were purged dry. Field measurements of temperature, conductivity, and pH were recorded during well purging (Attachment 3). 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. The groundwater samples were analyzed for BTEX, and TPH-G using EPA method modified 8020/8015. Dissolved BTEX and TPH-G were detected in groundwater samples from monitoring wells MW-1, 8, 9, and 10. The highest concentrations of benzene (52,000 parts per billion [ppb]) and TPH-G (12,000 ppb) were detected in the groundwater samples collected from well MW-10. Figure 4 illustrates the distribution of dissolved benzene and TPH-G concentrations in groundwater. The laboratory analytical reports and the chain-of-custody records for the .tune 30, 1994 sampling event are included in Attachment 4. 3094-M&S-APT(STHL-5) GROUNDWATER TECHNOLOGY .