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fJl. Scott Mansholt - 2 - 18 July 2008 Chevron OVP Former Tracy Pump Station CURRENT INVESTIGATION The purpose of the current investigation was to evaluate the downgradient extent of affected soil and groundwater within the UPRR easement, which is lateral and east of the Site. Four soil borings were completed at 12 to 23.5 feet below ground surface (bgs). A fifth' boring was completed onsite to 32 feet bgs to evaluate the vertical extent of affected groundwater. Seven hand auger borings and five step-out hand auger borings were completed onsite to depths of 10 feet to obtain soil samples for future health risk screening evaluation (HRSE) purposes. Depth to groundwater ranged between 8 and 13 feet bgs. Soil During the investigation five soil borings (SB), were advanced to between 12 and 32 feet bgs. Samples were collected between 5 and 18 feet and submitted for analysis. Sample results reported total petroleum hydrocarbons as crude oil (TPHc) at concentrations of 260 milligrams per kilogram (mg/kg) to 2,200 mg/kg (SB-16 at 10.5 feet bgs). According to the lithologic logs, separate phase crude oil was first noted in soil cuttings beginning at the groundwater interface, often extending below the top of the water table. The vertical extent of affected soil was defined by onsite boring SB-14 where the 31.5-foot soil sample was non-detect (ND) for TPHc and polynuclear aromatic hydrocarbons (PAHs). None of the soil boring or hand auger samples were analyzed for benzene, toluene, ethylbenzene, and xylenes (BTEX). Two soil samples, 12.5 feet (SB-18, offsite) and 22 feet bgs (SB-14, onsite), were submitted for fuel fingerprint evaluation to determine the source of the TPHc. The TPHc present was determined to be a degraded crude oil similar to San Joaquin Valley crude oil. The chromatogram evaluation noted a trace of gasoline-range hydrocarbons present in both samples. Twelve hand auger borings, advanced as offsets to earlier boring locations, were completed near former crude oil storage tanks located on the north part of the Site now occupied by an alfalfa field. Forty-eight soil samples were submitted for TPHc and PAH analysis for support of the HRSE. Analytical results of soil samples from the hand auger borings reported the presence of TPHc in at least one of four samples collected from each boring location. TPHc concentrations included a high of 9,600 mg/kg detected at a depth of ten feet near the center of one of the former onsite storage tanks. Consistent with analytical soil results at other OVP projects, elevated concentrations of PAH compounds detected in samples reporting 1,000 to 9,600 mg/kg TPHc in soil, exceeded respective Screening for Environmental Concerns at Sites with Contaminated Soil and Groundwater*' and/or Preliminary Remedial Goals*2. *1 - ESLs, from - San Francisco Bay Regional Water Quality Control Board, Interim Final, November 2007). *2—PRGs - U.S. Environmental Protection Agency (EPA) Region 9, Preliminary Remedial Goals, October 2004.