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Lee Higgins - 3 - 7 December 2010 Chevron, TAOC Tracy Rail Yard the toxicity equivalent (TEQ) to benzo(a)pyrene (BaP). Results for non-detect PAHs are set at half of the detection limit, the TEQ is determined and the value(s) are "added" into the total determination, resulting in a single cumulative BaP TEQ for all PAHs, which is used for estimating risk. Findings obtained during the soil vapor investigation will be used by UPRR's consultant in a future health risk assessment for the Site. Previously, offsite groundwater conditions were investigated along the former OVP/TAOC pipeline easement to the west and into the adjacent residential neighborhood. However, offsite soil and/or groundwater affected by historical crude oil leaks were not addressed as part of the current investigation, and will be evaluated separately by Chevron. Operable Unit 2 The historical TAOC pipelines crossed OU-2 from east to west, generally along the southern property boundary. The former OVP extended from the southeast to the central-east side of OU-2. Previous investigations identified TPH constituents present, including VOCs, semi- volatile organic compounds (SVOCs), and PAHs. The extent of crude oil affected soil and groundwater was not previously determined, and additional investigation was needed primarily along the historical crude oil pipeline alignments. Soil AMEC drilled 12 offset borings and collected 20 soil samples for analysis from locations where TPH compounds exceeding environmental screening levels were previously detected. TPH as crude oil (TPHc) was detected in 19 samples at concentrations ranging from 1.5 to 12,000 milligrams per kilogram (mg/kg) at sample depths of 6 to 18 feet bgs. With the exception of the latter TPHc result, the concentrations ranging from 940 to 1,500 mg/kg were reported in samples from borings completed on the north side of the historical TAOC alignment, along the southern property boundary. With exception of benzene detected in soil samples from a depth of six feet bgs from two borings at concentrations of 0.0005 and 0.0006 mg/kg, BTEX constituents were non-detect (ND). The 12,000 mg/kg TPHc reported was in a sample from a depth of six feet bgs collected from boring TRY-1 . The boring was near a historical aboveground storage tank (AST) at the terminus of the former OVP, along the central-east side of OU-2, where prior investigations reported petroleum hydrocarbon affected soil. A groundwater sample from this boring was submitted for analysis (see following discussion). AMEC indicated the AST is considered part of the former UPRR maintenance facility, and not the former OVP. Also, the TPHc concentration of 1,500 mg/kg reported in a sample from a depth of six feet bgs was associated with wood debris encountered in drill cuttings from boring TRY-13. TPH affected soil was otherwise not observed in this boring. AMEC concluded the petroleum hydrocarbon affected wood debris encountered was not associated with the former OVP/TAOC pipelines. Soil samples from three borings within OU-2 were submitted for fuel fingerprint determination. Analytical laboratory chromatograms indicate the TPH is consistent with weathered San Joaquin Valley crude oil. Indications of heavily weathered bunker fuel may be present in one