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%4r. Kyle Christie January 14, 1991 Page 2 E=xtraction Method 5030. Analytical resuits are summarized in Table I. The complete laboratory reports are enclosed as Appendix A. All groundwater produced during the sampling activity was removed from the site b;, Armour Petroleum. }I Table 1 irtclud-s the analytical results from ti<t groundwater samples collected over the past 2 years. BETX constituents were not identified above the detection lintels of 0.5 microgram per liter(Ag/l)in the September 1990 groundwater samples from wells PR-1,PR-0. and microgram er the remaining wells that were sampled in September 1990, BETX Of constituents were identified in wells BHD-1,E-2,E-4, E-5, E-7,E-8,E-9,E-I0, E-1 I,and E-12. The benzene concentradon exceeds California Department of Health Services(DHS)Maximum Contaminant Levels(MCLS) of 1 µg/1 in the samples from all of'hese wells. Benzene concentrations have varied in each well over time. The groundwater samples from wells E-5 and E-12 showed increases hi benzene concentration since they wore lase camnied in Tune 1990 and well E-7 showed an increase in benzene since it r.,as last sampled in March 1990: Decreases in benzene concentration were identified in the samples;-Om wells BHD-1,E-2,E"4, E-8, E-9, E-10, an E-11. A contour map of the benzene concentrations in the September 18. 1990 groundwater sampling event are shown on Figure The concentration of ethylbenzene is above the DHS MCL of 680 µg/1 in well E-5. The concentration of toluene is above the DHS Drinking Water Action Level of 100 gg/l in monitoring wells E-5 and E-9. The concentration of xylenes are above the DHS MCL of 1,750 gg/1 in monitoring wells E-5, E-9, and E-10. TPH concentratsons were nonclVectable in wells PR-1, PR-2, and BHD-2. Tate highest concentrations of TPH were detected in wells E-5, E-9, and E-10. No DHS MCL has been established for TPH. Groundwater Conditions Groundwater levels at the site are being measured in each.well by a Brown and Caldwell field technician on a twice-a-month basis using an electronic oil/water--level indicator. The levels are measured relative to top-of-casing elevations in order to determine groundwater elevations and monitor possible changes in flow. Table 2 shows the water-level measurements collected since January 1990. Figure 2 shows groundwater flow patterns at the site on September 17, 1990. The conditions} indicate groundwater flows to the northeast under a nearly flat gradient while this recovf-ry pump is not operating. This pattern and magnitude of gradient has been observed in each season over the past several years. Brown and Caldwell