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. 4.3 Extent of Petroleum Hydrocarbon Impact to Soil Available historical soil analytical data is provided in Appendix H TPHG and BTEX impact to soil was initially reported for soil samples collected during site assessment activities in the early 1990's TPHG and benzene were reported at concentrations of 300 mg/Kg and 0 36 mg/Kg, respectively, for a soil sample collected from boring B-7 at 10 feet bgs in 1991 Boring B-7 was advanced immediately adjacent to the former pump island, within the area occupied by the current UST complex (see Figure 2) Compliance soil samples were collected at the time of UST removal in March 1994 Depth to groundwater was measured at approximately 13 7 feet bgs (well MW-1) at this time (first quarter 1994 monitoring event) TPHG and benzene were reported at maximum concentrations of 880 mg/Kg and 3 5 mg/Kg, respectively, for samples collected from beneath the former USTs at 16 feet bgs Compliance soil samples were also collected during the excavation of the cavity containing the current USTs in December 1995, TPHG and benzene were reported at maximum concentrations of 400 mg/Kg and 1 0 mg/Kg, respectively, for a sample collected from the excavation sidewall at 11 feet bgs MTBE or TBA analysis was not performed on any soil samples collected during the early and mid 1990's site characterization activities Figure 9 presents a summary of soil analytical results for samples collected between approximately 6 and 17 feet bgs MTBE and TBA were reported in soil samples collected from borings CPT-2 and CPT-3 MTBE (3 2 mg/Kg) and TBA (69 mg/Kg) were reported for a sample collected from boring CPT-2 at 10 feet bgs MTBE (0 13 mg/Kg) and TBA (170 mg/Kg) were also reported for a • extends t sample collected from boring CPT-3 at 11 feet bgs MTBE and TBA impact o approximately 60 feet bgs in the vicinity of borings CPT-2 and CPT-3 Concentrations of MTBE and TBA ranged from 0 0078 mg/Kg to 0 057 mg/Kg and 1 3 mg/Kg to 10 mg/Kg, respectively, for samples collected from borings CPT-2 and CPT-3 between 24 and 61 feet bgs Petroleum hydrocarbon and fuel additive concentrations were reported below laboratory detection limits for the samples collected from borings CPT-4 through CPT-7, and samples collected from boring CPT-1 at 62 and 73 feet bgs TPHG and BTEX compounds were not reported above laboratory detection limits in any of the soil samples collected during the recent CPT investigation 44 Extent of Petroleum Hydrocarbon Impact to Groundwater Historical groundwater analytical data is included in Appendix F TPHG, BTEX, MTBE, and TBA impact to groundwater has been documented since installation of the monitoring wells in 1991 TPHG and benzene were reported at concentrations of 25,000 µg/L and 500 pg/L, respectively, from a grab groundwater sample collected during excavation of the current UST cavity in December 1995, MTBE and TBA analysis was not performed on this sample This grab groundwater sample was collected in close proximity to the future location of well VEW-3, immediately southeast (generally downgradient) of the former UST area, and immediately adjacent to the former pump island situated parallel to Ryde Avenue Limited MTBE analyses were performed prior to 1997, MTBE was reported at a maximum concentration of 220 µg/L (upgradient well MW-1, August 1997) K\USA Gaso1ine\0835\Reports\usa835 scm-assessment-report doc Page 9 OTIZATU5