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60 CONCLUSIONS AND RECOMMENDATIONS Gasoline-range petroleum hydrocarbons likely associated with smear zone impacts from fluctuating ' groundwater levels were detected within the soil samples obtained from well boring MW-14A TPHg was detected at relatively low concentrations of less than 10 mg/kg between depths of 9 0 and 13 5 meters (30 to 44 feet)bgs BTEX compounds of equal to or less than 10 mg/kg were further detected between depths of 4 5 to 15 meters (15 to 50 feet) bgs FOCs including MTBE were not detected in each soil sample analyzed The groundwater sample collected from well MW-14A contained TPHg and BTEX FOCs including ' MTBE were not detected in the well MW-14A groundwater sample Groundwater was sampled from four vertically discrete zones (16 5 to 17 4 meters [55 to 58 feet], ' 18 3 to 18 9 meters [61 to 63 feet], 19 5 to 20 1 meters [65 to 67 feet] and 21 to 21 6 meters (70 to 72 feet) bgs within the CPT boring These zones were selected based on review of the lithologic logs ' obtained from the initial CPT sounding and the ability to generate sufficient groundwater to sample The CPT log did not indicate a producable water-bearing zone below approximately 21 6 meters (72 feet) bgs and was terminated at 30 meters (100 feet) bgs to prevent penetration of a potential underlying confining layer The shallowest groundwater zone sampled, 16 5 to 17 4 meters (55 to 58 feet), contained similar dissolved phase TPHg and BTEX concentrations as the monitoring well MW-14A groundwater sample The deeper zone samples did not contain detectable TPHg or FOCs BTEX compounds were detected in the deeper zone groundwater samples but at relatively low 1 concentrations of less than 5 �tg/l Slight variations in the concentrations of hydrocarbons detected may be attributable to the lateral ' distance between the borings and the difference in sampling methodology between groundwater samples taken from a CPT bailer and a groundwater sample taken from a developed monitoring well ' Based on the CPT groundwater sampling, it appears that vertical migration of dissolved phase TPHg has generally been limited to the current shallow groundwater zone between 16 5 and 17 4 meters (55 to 58 feet) bgs The data presented herein should be utilized to evaluate the mass distribution of dissolved phase gasoline in groundwater It is recommended that quarterly groundwater monitoring ' continue at the Site to further evaluate the seasonal distribution of groundwater contaminants Project No S8475-06-02 -12- December 26,2001 1