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4.0 CONCLUSIONS AND RECOMMENDATIONS <br /> 1 <br /> Based on the results from previous investigations, most of the petroleum hydrocarbon mass <br /> appears to be concentrated in soil immediately below the north end of the former middle UST <br /> Vertically, the concentrations of gasoline hydrocarbons appear to decrease rapidly with depth <br /> Based on the results from soil samples collected during the drilling of MW-1, MW-2, MW-3 and <br /> MW-4, the lateral extent of impacted soil appears to be defined to the area of the former USTs <br />' Between September 18 and December 17, 2001, the groundwater surface rose an average of <br /> 1 39 feet, and the groundwater flow direction and gradient remained relatively constant <br /> Except for a low concentration of 0 55 µg11 of xylenes at MW-4, gasoline compounds were not <br /> detected in any of the groundwater samples collected during the investigation As such, any <br />' impact to groundwater appears to be limited to immediately beneath the former USTs <br /> Based on these conclusions, Ramage Environmental recommends that the monitoring well <br /> network continue to be monitored and sampled on a quarterly basis for at least two additional <br /> quarters The next groundwater monitoring is scheduled for March 2002 If, after the next two <br /> quarters of sampling, groundwater continues to be free of gasoline compounds, the case should <br /> be considered for regulatory closure <br /> 1 <br /> i <br />' 15 <br /> t <br />