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' k'q KLEINFELDER 6 CONCLUSIONS ' 6.1 Conclusions ' 6.1.1 Soil Based upon the analytical results, it appears that the majority of the petroleum hydrocarbon ' impacted soil is confined to the former UST excavation The greatest concentrations of TPH extractable as diesel were reported in samples collected from GP-1 and GP-9, both located within the former UST excavation TPH purgeable as gasoline was reported in one sample collected ' from the former UST excavation MTBE was reported in three samples collected from the former excavation No BTEX compounds were detected in any of the soil samples collected The analytical results from the excavation do not show a consistent pattern This is likely due to ' the use of native material, imported fill and hydrocarbon affected soil to backfill the excavation ' No TPH purgeable as gasoline, MTBE or BTEX compounds were reported in soil samples ' collected outside of the former UST excavation area (GP-4, -5, -6, -7, -8, -10, -11, -12, -13) Low concentrations of TPH extractable as diesel ranging from 16 to 52 mglkg were reported in samples collected outside of the former UST excavation area The majority of the sample results outside of the excavation area were below 10 mg/kg Groundwater fluctuations at deeper depths may account for the detected concentrations above groundwater ' 6.1.2 Groundwater ' As with the soil at the site, the bulk of the groundwater impacts at the site appears to at or near (within 25 feet) of the former UST excavation BTEX compounds were reported in groundwater samples collected from GP-1, -2, -3, and—9, located within or immediately adjacent to the former UST excavation Benzene was reported at concentrations above the California Primary Maximum Contaminant Level (MCL) of 1 ug/L Toluene, ethylbenzene, and xylene were detected in the groundwater samples obtained from within or adjacent to former UST excavation, but were all below the California MCLS MTBE was also detected in groundwater in samples collected within the former UST location and extending to the east approximately 30 feet from the east edge of the former UST excavation The concentrations of MTBE detected ranged from 0 59 to 36 ug/L The California Environmental Protection Agency (Cal EPA) has established a water quality goal of 5 ug/L for MTBE TPH purgeable was detected in four groundwater samples, collected from within the former tank excavation area (GP-1, -2, -3, -9) and west of the former excavation at GP-11 The concentrations ranged from 0 15 to 187 mg/L The concentrations detected are above the U S EPA suggested no adverse response level (SNARL) of 5 ug/L(0 005 mg/L) ' 20-2322-05 E01/20118061 Page 11 of 14 Copyright 2001,Kleinfelder, Inc January 12,2001