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KLEINEELDER <br /> approximately S feet west of the fence; and the sample collected at an auger depth of 40 <br /> feet was approximately 13 feet west of the fence. Based on the results of the three samples <br /> (20, 25, and 40 feet) from boring B-1, there does not appear to have been significant lateral <br /> ' migration of petroleum hydrocarbons beneath a depth of 20 feet. <br /> Soil boring B-2 was drilled vertically through the center of the removed 500-gallon tank <br /> ' excavation. This boring was located approximately 5 feet away from the second area where <br /> elevated TPH concentrations were previously reported at a depth of 16 feet. Excavation <br /> backfill material was encountered to an approximate depth of 22 feet. Soil samples were <br /> collected and analyzed at 25, ,30 and 40 feet. A low concentration of xylenes <br /> (0.0072 mg/kg) was detected at 30 feet, and a low concentration of TPH-Diesel <br /> (1.5 mg/kg) was detected at 40 feet. This is much lower than the TPH-Gasoline <br /> ' concentration of 23,000 mg/kg previously detected at 16 feet. Analytical results indicate <br /> that there has not been a significant component of vertical migration in the vicinity of <br /> boring B-2. <br /> 5.2 GROUND WATER SAMPLING <br /> Ground water monitoringwell MW-1 <br /> was constructed through the approximate center of <br /> ' the combined excavation of the three tanks. The well was installed through the center of <br /> the excavation in an attempt to sample ground water directly beneath the removed tank in <br /> an area likely to be impacted by the vertical migration of petroleum hydrocarbons. This <br /> ' was done in lieu of installing three ground water monitoring wells around the perimeter of <br /> the excavation area. <br /> FR1-92-15 Page 15 of 21 <br /> Copyright 1992 Kleinfelder,Inc. <br />