SITE INFORMATION AND CORRESPONDENCE

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No Further Action Required Determination -2 - 6 January 2011 Banta Road-UPRR Tracy-Fresno Line Tracy, San Joaquin County Consistent with State Water Resources Control Board (State Water Board) Resolution No. 92-049, Section III, A through C, SAIC evaluated alternative cleanup technologies and found that processes other than natural attenuation would be ineffective, infeasible, and disproportionally costly. Residual crude oil concentrations will naturally degrade with time. Issues: Petroleum hydrocarbon affected soil was observed during the installation of a water pipeline beneath South Banta Road. The boring was also drilled under the UPRR tracks and the historical crude oil pipelines which ran along the southwest side of the tracks and former pipeline alignment. Onsite soil affected by TPHc is generally defined onsite, beneath and within the highway right-of-way easement. Groundwater impacts identified at the Site consist primarily of crude oil (analyzed as TPH as diesel (TPHd)). Groundwater affected by petroleum hydrocarbons/crude oil has been delineated onsite. The TPHd concentrations reported do not exceed screening levels. Setting: Open, agricultural land is adjacent on all sides with a limited number of industrial properties, primarily to the north and south along South Banta Road, and few single family rural residences. The Tracy Defense Depot is to the east. It is anticipated that future land use at the Site will remain unchanged since it is located within the South Banta Road right- of-way easement. Source: Leaks from the historical TAOC/OVP crude oil pipelines located approximately 100 feet south of the Site. The historical pipelines operated from the early 1900's to the 1970's, and were removed from service during the late 1960's to early 1970's. Actions: Preliminary soil/groundwater investigations beginning in 2003. • In December 2003, petroleum hydrocarbon affected soil was observed during a horizontal jack-and-bore excavation for the installation of a large diameter water pipeline. The boring was drilled under South Banta Road, the UPRR tracks, and the historical crude oil pipelines which ran along the southwest side of the tracks and former pipeline alignment. Crude,oil affected soil was observed at excavation depths of between 11 and 19 feet below ground surface (bgs); soil samples collected during the excavation were analyzed for TPH compounds. The analytical results were non-detect (ND) with two exceptions which exceeded environmental screening levels for potential future onsite residents. TPH at a concentration of 2,400 milligrams per kilogram (mg/kg) and 0.082 mg/kg ethylbenzene exceeded the residential screening levels of 370 and 0.0019 mg/kg, respectively. However, these values do not exceed applicable environmental screening levels for a future construction/trench maintenance worker, which is the anticipated future onsite environmental risk exposure scenario. • Central Valley Water Board staff directed Chevron to conduct an additional investigation to define/evaluate the extent of crude oil affected soil and/or groundwater. In November 2008, additional borings were drilled, and soil and groundwater samples collected for analysis of TPH compounds. Visually affected soil was not observed and the results of TPH analyses did not exceed respective environmental screening levels for soil and/or were ND for the site TPH compounds described above. • Groundwater samples were analyzed for TPHd, benzene, toluene, ethylbenzene, and xylenes (BTEX), and polynuclear aromatic hydrocarbons (PAHs). Water samples were