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Lee Higgins - 5 - 7 December 2010 Chevron, TAOC Tracy Rail Yard respective laboratory reporting limits. However, low concentrations of toluene, ethylbenzene, and xylenes were detected in the four samples. No analytes were detected above their respective residential or commercial environmental screening levels. Operable Units 3 and 4 As noted above, the City of Tracy recently completed construction of a regional transit facility on the two parcels. The historical TAOC pipelines crossed east-west, adjacent to the southern property boundary of OU-3. The former OVP was apparently not present in either parcel. Similar to OU-2, TPH affected soil and groundwater were detected primarily along the west side of the two units, adjacent to and slightly north of the former TAOC pipelines. The extent of affected soil and groundwater were not previously delineated. AMEC drilled three offset borings in OU-3 and one in OU-4, for collecting samples to determine the lateral extent of the impacts. Soil According to the Report, analytical results for soil samples in OU-3 shallow borings from approximately five feet bgs were ND for TPHc; benzene at 0.0007 mg/kg was detected in one sample. The remaining analyses were ND for the TEX compounds. Samples from the same boring at depths of 21 and 27 feet bgs were ND for TPHc, BTEX and PAHs. Analysis of the sample from a depth of 18 feet bgs in the OU-4 boring indicated a concentration of 1,700 mg/kg TPHc. Prior offset borings located approximately 100 feet north within OU-4, did not report TPH compounds or visually affected soil. Soil samples from two borings within OU-3 and 4 were submitted for fuel fingerprint determination. The laboratory chromatograms indicate the TPH present in both samples are consistent with weathered San Joaquin Valley crude oil. Groundwater Groundwater samples collected at different depth intervals from one of the borings were submitted for TPH analysis. Five grab samples from 4 to 5-foot thick intervals were collected from depths of between 29 and 66 feet bgs. TPHd concentrations ranged from 51 to 100 tag/L; the fifth interval sampled at a depth of 44 to 48 feet bgs, reported TPHd at a concentration of 370 pg/L. Lateral offset borings completed in 2006 — 2008, discussed in the preceding paragraph, also included collection and analysis of groundwater samples which reported TPHd ranging from ND to 110 and 130 pg/L. PAHs and BTEX constituents in groundwater were ND. Affected soil was not noted in the offset borings, thus the lateral downgradient extent of crude oil affected soil and groundwater in OU-3 and OU-4 was defined by these findings. The vertical extent of affected groundwater was defined by TPHd concentrations of 51 to 100 tag/L at depths of approximately 50 to 56 feet bgs.