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1 File : W-2017-1/11 : 308 <br /> June 26 , 1986 <br /> 1 Page 7 <br /> 1 VI . DISCUSSION AND INTERPRETATION OF RESULTS <br /> Data obtained from PID readings and analytical results <br /> indicate the presence of gasoline-related constituents in the <br /> 1 soil adjacent to and below the tank excavation area. Low <br /> concentrations of benzene , tolulene , and xylene were detected in <br /> three of the five soil samples analyzed. <br /> 1 The concentrations of ethyl dibromide and total hydrocarbons <br /> were below detectable limits in all five soil samples . The <br /> 1 concentrations of total lead detected in the soil samples was <br /> typical of background soil concentrations . <br /> Significant PID readings were first recorded at a depth of <br /> 1 15 feet below the ground surface . PID readings were generally <br /> higher in the sandy material were volatile constituents can move <br /> more easily through the larger pore spaces in the soil . The <br /> 1 highest PID reading (549 . 3 ppmv) was recorded from the soil <br /> sample collected from a depth of 50 feet below the ground <br /> surface. This sample was collected from a fine to medium grain <br /> 1 sand five feet above the water table . All constituents were <br /> below detectable limits in the soil sample chemically analyzed <br /> from this depth (MW-1-50A) . The high PID reading and the lack of <br /> detectable constituents in soil sample MW-1-30A indicates that <br /> 1 volatiles are migrating up from the water table through the pore <br /> spaces in the sand. <br /> 1 Analytical results from water sample MW-1-69-A indicate that <br /> benzene ( 382 DDb) toluene ( 115 ppb) , and xylene ( 58 . 3 ppb) are <br /> present in the ground water below the tank excavation. The <br /> concentrations of benzene and toluene detected by the analytical <br /> 1 laboratory are above State action levels . The concentrations of <br /> ethyl dibromide, total hydrocarbons , and total lead are below <br /> detectable limits in the water sample . <br /> 1 The extent of migration of gasoline-related constituents in <br /> the ground water and the ground water gradient are not known at <br /> 1 this time. Information obtained from additional monitoring wells <br /> would be necessary to understand the local ground water gradient <br /> and the extent of gasoline constituents in the ground water . <br /> 1 <br /> 1 <br /> 1 <br /> 1 <br /> r <br />