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fN <br /> l <br /> DISCUSSION <br /> Laboratory results for this and previous quarterly ground water monitoring and sampling <br /> events are summarized in Table 1 A ground water elevation contour map for March 1992 <br /> is shown in Figure 3, and concentrations of dissolved-phase hydrocarbons are shown in <br /> Figure 4 Results of this sampling event are summarized below• <br /> • Between the December 1991 and March 1992 sampling events, free product <br /> thickness in MW-3 decreased from 0 06 to 0 01 <br /> • Concentrations of TPH-G and benzene have apparently increased to detectable <br /> concentrations in the ground water samples collected from MW-2, AMW-5, and <br /> AMW-6 <br /> • Consistent with past results, concentrations of TPH-G and BTEX were not detected <br /> at or above reported detection limits in ground water samples from Monitoring <br /> Wells MW-1, MW-7, and AMW-1 through AMW-4 <br /> • The average depth to water during this monitonng event is approximately 5 2 fbg <br /> (20 8 feet above mean sea level) The average ground water gradient direction is <br /> estimated to be toward the north/northwest, with a magnitude of 0 005 foot/foot <br /> across the site Both gradient direction and magnitude are consistent with historical <br /> trends <br /> ALTON GEOSCIENCE <br /> 4 <br /> Stephan R <br /> Senior Geologist <br /> PeterngqR5089 <br /> Associate, Northern California Operations <br /> 2 <br />