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i Rii I SU6SUF.=AM INV[:SRif3ATCK RESULTS p.,.T 1605 South£I Dorado.Stockton.Callomia 3.3 Groundwater Conditions On July 11, 1991,Aegis personnel collected measurements of the depths-to-groundwater 3 in wells MW-1, MW-2, and MW-3 (Table 2). On the basis of the measurements, groundwater is estimated to flow to the southeast direction (Figure 3) at an average ' 9radient of approximately 0.0006 ft/ft. Figure 3 is a pot entiometric surface map of the shallow water-bearing zone on July 11, 1991. Groundwater elevation measurements were made from the referenced wellhead trt� elevaticns, measured to the nearest 0.01 foot. The well locations are based on .. coordinates measured from a chiseled"plus"mark in the sidewalk on the northeast corner of the site. The wells were surveyed by Wong Engineering of Stockton, California. (. 3.4 Groundwater Sampling 1, Water samples were collected from the three purged wells on July 11, 1991,and delivered under chain-of-custody to Coast-to-Coast Analytical Services in Benicia, California, for analyses. The samples were analyzed for TPPH as gasoline, BTEX, EDB, EDC by CAL F DHS (TPH draft method) and EPA Method 8240/8260, and total lead by EPA Method 7421. The laboratory results reports and chain-of-custody forms are located in Appendix B. 3.5 Analytical Results: Soil E Nine of the twenty-seven soil samples collected from MW-1 through MW-3 were delivered to Coast-to-Coast Analytical for analyses. Laboratory analysis of all soil boring and soil pile samples indicated concentrations of BTEX, EDC, EDB, and TPPH as gasoline below method detection limits except for sample E-MW-3 at 20.5 feet which indicated toluene and total xylenes at 0.01 ppm. The organic lead results for the soil pile sample were also below method detection limits. One soil sample was taken at the air/water interface in each well. Table 3 summarizes the analytical laboratory results for the soil samples collected. 3.6 Analytical Results_Groundwater V Laboratory analysis of monitoring well MW-1 reported below detection limit for concentrations of BTEX, EDC, EDS, TPPH as gasoline, and total lead. Monitoring well MW-2 reported below detection limit for concentrations of constituents analyzed except benzene at 0.5 parts-per-billion (ppb) and TPPH as gasoline at 140 ppb. Monitoring well MW-3 reports concentrations of benzene at 9.0 ppb, toluene at 1.5 ppb, total xylenes at 78.0 ppb, and TPPH'as gasoline at 940.0 ppb. Total lead was below detection limit for x the three groundwater samples. Refer to Table 3 for summarization of analytical results. ------= --------- ----- ---- ---- r----------Figure-4-is-a-distribution-map-of TPH-as gasoline-and benzene ri groundwater