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Michael Oliphant -2 - 22 March 2012 Chevron TRY Offsite-West, Tracy • TPH affected soil noted at three boring locations in samples obtained at/near the water table (approximately 18 feet bgs) was analyzed. TPHc was detected at concentrations ranging from 400 to 810 mg/kg. Ethylbenzene concentrations, ranging from 0.0074 to 7.2 mg/kg, were detected in three soil samples collected at approximate depths of between 18 and 35 feet bgs. Benzene, toluene, and xylenes were non-detect (ND) in soil samples collected during the investigation. • Polynuclear aromatic hydrocarbon (PAH) compounds were detected in 5 of 22 soil samples submitted for analysis. AMEC calculated the benzo(a)pyrene toxicity equivalents (BaP TEQs) for each sample that had at least one carcinogenic PAH (which was chrysene). Chrysene was detected at concentrations of 0.032 to 0.14 mg/kg in three soil samples at depths between 18 and 35 feet bgs. The BaP TEQ was determined at 0.005 to 0.023 mg/kg. AMEC reported these values will be considered in a future human health risk assessment. • Analytical results from one soil sample collected at 18.5 foot bgs that was submitted for fuel fingerprint evaluation, indicated that the TPH present resembled weathered San Joaquin Valley crude oil, considered to be associated with the TAOC crude oil pipelines. • Two of the offset borings were completed on vacant land to the north, to collect samples for evaluating groundwater at the downgradient locations. A third water sample was collected for analysis from one of the other soil borings. • TPH as diesel (TPHd) and benzene, toluene, ethylbenzene and xylenes (BTEX) were ND for the samples collected from the two downgradient borings. AMEC concluded that the ND results define the lateral downgradient extent of affected groundwater. • Analysis of samples from borings drilled to evaluate deeper groundwater (70 and 90 feet bgs) reported TPHd concentrations of 130 to 850 micrograms per liter (Ng/L). The results were denoted as "J" values by the laboratory, which indicate the compound was detected but determined to be an "approximate" value. Laboratory review of the chromatogram indicates the TPH is very different from known San Joaquin Valley crude oil, indicating that the TPHd detections in the deep samples are unrelated to crude oil such as from the historical TAOC pipelines. • BTEX compounds were ND for groundwater samples collected during the investigation with the exception of ethylbenzene at 4.1 pg/L (and 4.3 pg/L for the duplicate), reported in the samples collected at about 50 feet bgs. • PAHs at low concentrations were reported in three different water samples, but carcinogenic compounds were ND, therefore the BaP TEQs were also ND. • The Report concluded that since the results of the deeper water samples indicated a non-TAOC pipeline source, the vertical extent of crude oil affected groundwater was defined. • According to the Report, based on the earlier findings in conjunction with the recent characterization results, the lateral and vertical extent of affected soil and groundwater has been delineated and additional investigation was not warranted.