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s <br /> E <br /> Mr. Kyle.Chrisde <br /> January 14, 1991 <br /> Page 2 <br /> t. <br /> Extraction Method 5030. Analytical results are summarized in Table I. The complete laboratory <br /> reports are enclosed as Appendix A. All groundwater produced during the sampling activity was <br /> removed from the site by Armour Petroleum. <br /> Table 1 includes the analytical results from the groundwater samples collected over the past 2 <br /> years. BETX constituents were not identified above the detection limits of 0.5 microgram per <br /> liter(µgll)in the September 1990 groundwater samples from wills PR-1,PR-2,and BHD-2. 4f <br /> the remaining wells that were sampled in September 1990, BETX constituents were identified <br /> in wells BHD-1,E-2,E-4,E-5,E-7,E-8,E-9,E-10,E-11,and E-12. The benzene concentration <br /> exceeds California Department of Health Services(DHS)Maximurn Contaminant Levels(MCLS) <br /> of 1 µg/1 in the samples from all of these wells. <br /> Benzene concentrations have varied in c sch well over time. The groundwater samples from wells <br /> E-5 and E-12 showed increases in benzene concentration since they wem last sampled in June <br /> 1990 and well E-7 showed an increase in benzene since it was last sampled in March 1990. <br /> Decreases in benzene concentration were identified in the samples from wells BHD-1,E-2,E-4, <br /> E-8, E-9, E-10, an E-11. A contour map of the benzene concentrations in the September 18, <br /> 1990 groundwater sampling event are shown on Figure 1. <br /> l 'Me concentration of ethylbenzene is above the DHS MCL of 680 µg1l in well E-5. The <br /> concentration of toluene is above the DHS Drinking Water Action Level of 100 p&I iu <br /> monitoring wells E-5 and E-9. The concentration of xyleries are above the DHS MCL of 1,750 <br /> µg/1 in monitoring wells E-5, E-9, and E-10. <br /> TPH concentrations were nondetectable in wells PR-1, PR-2, and BHD-2. The highest <br /> concentrations of TPH were detected in wells E-5, E-9, and E-10. No DHS MCL has been <br /> established for TPH. <br /> Groundwater Conditions <br /> Groundwater levels at the site are being measured in each well by a Brown and Caldwell field <br /> technician on a twice-a-month basis using an electronic oillwater-leve!indicator. The levels are <br /> measured relative to top-of-casing elevations in order to determine groundwater elevations and <br /> monitor possible changes in flow. Table 2 shows the water-level measurements collected since <br /> January 1990. Figure 2 shows groundwater flow patterns at the site on September 17, 1990. The <br /> conditions indicate groundwater flows to the northeast under a r early flat gradient while this <br /> recovery pump is not operating. This pattern and magnitude of gradient has been observed in <br /> each season over the past several years. <br /> Brown anti Calthvell <br />