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monitored on a quarterly basis throughout 1992 No detectable diesel or volatile petroleum <br /> hydrocarbon concentrations have been encountered in any of these samples <br /> Analysis of groundwater samples collected from the off-site boreholes SB-l through SB-6 <br /> revealed no detectable diesel concentrations Samples from boreholes SB-1 through SB-4 and <br /> SB-6 revealed no detectable volatile petroleum hydrocarbons The water sample collected <br /> from borehole SB-5 revealed 0 8 ppb toluene only, at a detection limit of 0 3 ppb Analytical <br /> results are lasted in Table 3 and depicted in Figure 5 <br /> 4.o Conclusions <br /> 1 <br /> Groundwater was encountered at an average depth of 46 feet below grade during <br /> the drilling of boreholes SB-I through SB-6 <br /> • Groundwater elevations measured in the on-site monitoring wells MW-1 through <br /> MW-3 in December 1992 averaged 46 feet below grade and 33 feet below mean <br /> sea level. <br /> • Groundwater flow direction and gradient, calculated from monitoring well data <br /> collected in December 1992, was to the northeast at 0 013 ft/ft <br /> Analysis of soil samples collected near the abandoned diesel tanks indicated <br /> diesel concentrations up to 13,000 ppm <br /> • Analysis of soil samples collected during installation of monitoring wells MW-1 <br /> through MW-3 revealed no diesel concentrations. Volatile hydrocarbons were <br /> encountered an soil samples collected from well MW-1 (40 feet below grade) <br /> and well MW-3 (20 feet below grade) upon analysis These volatile <br /> hydrocarbon levels were at or slightly above method detection limits <br /> • Analysis of groundwater samples collected during installation of monitoring <br /> wells MW-1 through MW-3 revealed the presence of diesel an the samples <br />' collected from wells MW-1 and MW-2 (130 ppb and 52 ppb respectively) No <br /> diesel was encountered in the sample collected from well MW-3, upon analysis <br /> No volatile hydrocarbons were encountered in samples from any well <br /> • Analysis of groundwater samples from wells MW-1 through MW-3 collected <br /> during four consecutive quarterly monitoring events have revealed no detectable <br /> diesel or volatile hydrocarbons <br /> MZ/03-17-93/ENG/93-0o34 jf 7 <br />