SITE INFORMATION AND CORRESPONDENCE

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C. Scott Mansholt - Chevrof - 2 - 19 June 2008 Mountain House #4 mg/kg ethylbenzene at 16 feet in MH4-1. The lithologic log for MH4-1 indicated petroleum affected soil was noted from approximately six to 36 feet. At 44 feet, the maximum depth sampled in boring MH4-1, TPHc was ND. Samples for the other four borings reported TPHc at concentrations from ND to 13 mg/kg. Soil samples from boring MH4-6 near the BAPL and Kinder Morgan pipelines (both within the ROW), reported concentrations of TPHc of 17 to 9,100 mg/kg, respectively at depths of 1 tol 1 feet, with ND at 23 feet. At 8.5 feet, TPH as gasoline (TPHg) was reported at 3,200 mg/kg with xylene concentrations at 7.1 mg/kg and naphthalene concentrations of 43 mg/kg. The soil sample from eight feet was submitted for fuel fingerprint evaluation. Review of the chromatogram suggested that presence of a refined product(s), possibly from either or both of the two active pipelines. According to the evaluation report, the TPH present ..."has a carbon range from about C11 through C15, and a median at approximately C13. It is not typical jet fuel for the presence of branched paraffin's in abundance. At this boiling range, the sample could be kerosene, heating fuel#1, diesel#1, and/or jet fuel combination. There is an extremely weathered and very small amount of San Joaquin Valley crude oil present." SAIC stated that based on the fuel fingerprint evaluation, the TPHg constituents present are likely associated with a leak from either or both of the active refined product pipelines and not the former OVP. With the exception of the MH4-6 samples, concentrations of polynuclear aromatic hydrocarbons (PAHs) at or slightly above the method detection limits (MDLs) for the respective compounds were reported for the other borings' samples. BTEX and PAH detections were generally associated with samples reporting the presence of TPHc. Groundwater The depth to groundwater is currently approximately 12 to 18 feet. Based on monitoring wells associated with other nearby Mountain House Development OVP/TAOC sites, the local gradient is north-northeast. Analytical results of five groundwater samples reported concentrations of TPH as diesel (TPHd) at 62, 170, 130,000 micrograms per liter (pg/L), respectively for borings MH4-1, 4, and 6. Samples from MH4-5 and MH4-7 were ND. Groundwater samples from MH4-6 noted TPHg at 2,400 pg/L and BTEX compounds respectively were 1 pg/L, ND, 5 pg/L, and 11 pg/L. The highest PAH concentration reported was naphthalene at 640 pg/L. The remaining PAHs were ND, with some reported at or slightly above the laboratory MDLs and/or the Environmental Screening Levels (ESLs) described in - Screening for Environmental Concerns at Sites with Contaminated Soil and Groundwater, interim Final, San Francisco RWQCB, November 2007. Soil and groundwater analytical results are compared to the ESLs when evaluating the health risk and hazard index at petroleum constituent affected sites during the closure process. To assess general groundwater quality, representative samples were analyzed for concentrations of total dissolved solids (TDS) during earlier investigations at the adjacent Mountain House Development OVP/TAOC sites. The TDS values were approximately 1,500 milligrams per liter (mg/L). The Water Quality Control Plan for the Sacramento River Basin and the San Joaquin River Basin (Basin Plan) considers groundwater a potential source of drinking water provided it does not exceed TDS of 3,000 mg/L and yields at least 200 gallons