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i i I Second Quarter 1997 Monitoring and Sampling Report 2 f.� The Southtand Corporation,455 Grant Line Rd Tracy,CA July 11 1997 measured to the nearest 0 01 foot from the top of the well casing using an ORS Environmental Equipment INTERFACE PROBE Well Monttonng System Separate-phase hydrocarbons were not detected in any of the monitoring wells The water table elevations, calculated from the May 12, 1997 monitoring data, were used to prepare a potentiometnc surface map(Figure 2) The groundwater flow is generally toward the east/northeast at a hydraulic gradient of 0 004 ft/ft Groundwater monitoring results from the May 12, 1997 monitoring and sampling event are presented in Table 1, and historical results are summarized in Table 1A (Attachment 2) Field data sheets are included in Attachment 3 Monitoring Well Sampling and Analytical Results Groundwater samples were collected from wells MW-4, MW-5, MW-8, MW-9, and MW-10 Before sampling, at least four well-casing volumes of groundwater was removed from each monitoring well, unless the well was purged dry Field measurements of temperature, conductivity, and pH were recorded during well purging The groundwater samples were collected using disposable bailers and placed to analysis-specific sample containers with analysis-specific preservatives The samples were then sealed and labeled with the fob 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 Core Laboratories in Anaheim, California The groundwater samples were analyzed for BTEX, MTBE and TPH-G using Environmental Protection Agency (EPA) methods 8020/modified 8015 Groundwater purged during the first quarter monitoring and sampling event was pumped through the groundwater extraction system Dissolved benzene and TPH-G were detected in groundwater samples from monitoring wells MW-8, MW-9 and MWA0 with highest concentrations reported in MWA0 at 7,900 micrograms per Inter(pg/L) and 36,000 pg/L, respectively (Figure 3) MTBE was reported in MW8 and MW-9 at 19 micrograms per liter(pg/L) and 120 pg/L, respectively Analytical results from the groundwater samples collected on May 12, 1997 are presented in Table 1, and historical analytical results are summarized in Table 1A The laboratory analytical reports and the chain-of-custody records for the May 12, 1997 sampling event are included in Attachment 4 I 04660297 RPT(STHL1i 1) FLUOR DANIEL GTI