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8 15 feet to 10 72 feet. Groundwater has risen an average of 138 feet since the September <br /> 1993 monitoring This is a reversal of the decrease in groundwater depth observed between <br /> March 1993 and September 1993 <br /> Based on depth-to-groundwater measurements in monitoring wells MW-1, MW-2 and MW- <br /> 3, the hydraulic gradient was calculated to be 0 0026 ft/ft directed N 170 W The gradient <br /> appears to steepen towards the north (Figure 3) The flow direction and gradient are similar <br /> to those of previous monitoring events <br /> al ical Results of Water Sam <br /> 4.2 Analytical les p <br /> TPH as gasoline and diesel were detected in the water samples from MW-1 at <br /> concentrations of 5,100 ppb and 700 ppb, respectively Benzene, toluene and xylenes were <br /> detected in MW-1 at concentrations of 93 ppb, 21 ppb and 670 ppb, respectively Only <br /> ethlylbenzene was detected in MW-4 at 0 44 ppb No petroleum hydrocarbons were detected <br /> in samples from MW-2 or MW-3 The analytical results are summarized on Table 2 The <br /> laboratory report and chain-of-custody are included in Appendix B <br /> 4.3 Analytical Results of Stockpile Samples <br /> No petroleum hydrocarbons were detected in the soil sample collected form the remaining <br /> stockpiled soil on March 25, 1994 The laboratory report and chain-of-custody are included <br /> in Appendix B <br /> 5.0 CONCLUSIONS & RECOMMENDATIONS <br /> 5.1 Groundwater Depth and Gradient <br /> Three quarters of groundwater monitoring have been completed at this site A consistent <br /> 9 g g P <br /> groundwater flow direction west of north has been established The depth to groundwater <br /> has fluctuated since the first wells were installed in 1988, but has remained within 15 feet <br /> of surface grade <br /> 5.2 Petroleum Hydrocarbon Impacted Groundwater <br /> In MW-1, concentrations of TPH as gasoline have fluctuated between 2,300 ppb and 5,100 <br /> ppb during the last 3 monitoring events Initially the concentrations were as great as 80,000 <br /> ppb (January 9, 1990) TPH as diesel has also fluctuated between 520 ppb and 1,800 ppb <br /> No petroleum hydrocarbons have been detected consistently in MW-2 or MW-3 Traces of <br /> ethylbenzene were detected in MW-4 in the March 1994 sample (see Table 2), indicating <br /> that the petroleum hydrocarbon plume extends approximately 50 feet north of MW-1 (see <br /> Figure 4) <br /> ambyal A-dd S.—Ir. ^7 <br /> 5e -Ek...QX"9401S / <br /> r <br />