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r <br /> 4 0 CONCLUSIONS AND RECOMMENDATIONS <br /> r <br /> Based on the results of the project to date, gasoline compounds appear to have leaked from the <br /> ' former UST system, impacting subsurface soil and groundwater <br /> In soil, gasoline compounds appear to be limited to the vicinity of the former UST and <br /> underground piping, within an interval approximately five feet thick The vertical extent of <br /> impacted soil appears to be defined below 20 feet bgs Based on this distribution, approximately <br /> 331 62 pounds (44 2 gallons) of gasoline appear to be sorbed to soil <br /> In groundwater, the highest concentrations of gasoline compounds appear to be limited to the <br /> southern end of the former UST and approximately 50 feet away from the source Based on this <br /> distribution, approximately 1 14 pounds (0 15 gallons) of gasoline appear to be dissolved in <br /> groundwater \� <br /> Over the first six quarters of groundwater sampling and analysis, the plume of impacted <br /> groundwater appeared to be defined in the downgradient direction and concentrations of gasoline <br /> compounds appeared to be declining slightly In the past two quarters, MTBE was detected in the <br /> perimeter wells (MW-2 and MW-3), indicating that the plume may be migrating downgradlent of <br /> the source area <br />' Since the concentrations of MTBE in the downgradient wells do not exceed water quality goals, <br /> additional characterization may not be necessary However, the concentrations of gasoline <br />' compounds in groundwater should continue to be monitored and sampled on a quarterly basis to <br /> further evaluate the plume of impacted groundwater <br /> 1 <br /> 1 <br /> 1 <br /> 1 <br /> r <br /> • 12 <br />