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KLEINFELDER 4. RESULTS AND CONCLUSIONS 4 1 CONFIRMATION SAMPLING Total petroleum hydrocarbons extractable were detected in six of the excavation samples collected at concentrations ranging from 290 to 1300 mg/kg Two samples collected at depths of 13 and 15 feet along the north and east excavation sidewalls were nondetect for TPH extractable TPH extractable was detected at 1,300 mg/kg at a depth of 12 feet along the northwest sidewall and ranged from 290 to 1000 mg/kg in three for the four samples collected at the excavation bottom at depths of 20 to 21 feet The total recoverable petroleum hydrocarbons analyzed in three of the samples by an IR method were consistent with the TPH extractable results TPH purgeable was detected in all three of the samples submitted for that analysis The TPH purgeable concentrations ranged from 110 to 630 mg/kg BTEX constituents were not detected in the six samples submitted for that analysis Volatile and semi-volatile organics typical of petroleum hydrocarbons were detected at low levels in the samples 4 2 FORENSIC TESTING When it became apparent that petroleum hydrocarbons were present in the excavation to a depth of 21 feet, even with the removal of an additional 900 in-place cubic yards Independent Trucking Company elected to conduct forensic testing on two additional samples The purpose of the forensic analysis was to determine the type of petroleum hydrocarbon present and the approximate age of the material based on degradation patterns Two samples were collected on September 24, 1996 and submitted to Friedman & Bruya, Inc in Seattle One of the samples was nondetect, however the other sample had 700 mg/kg of extractable TPH According the Friedman & Bruya, the material in sample SSB1-21 appeared to be a biologically weathered diesel #l/kerosene as apparent by the lack of a prominent pattern of n-alkanes from about 7 minutes to around 14 minutes on the GC/FID chromatogram This material appeared to be mixed with a diesel #2/home heating oil that is less weathered as apparent by the presence of an even pattern of n-alkanes from about 14 minutes to 24 minutes An enriched level of the biomarkers przstane and phytane at about 17 and 18 minutes is another indication of a mixture of weathered and unweathered middle distillates 23-482276-BOO/CR96S276 Page 7 of I 1 October 17, 1996 Copyright 1996 Kleinfi.lder Inc