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M. Scott Mansholt -2 - 26 January 2010 Chevron Environmental US Can-Welty Road, Vernalis Site, and for adjoining properties that may be affected. Twenty-seven borings were drilled to depths of between 10 and 88 feet below ground surface (bgs) to collect soil and groundwater samples for analysis of the constituents of concern. Soil samples were submitted for fuel fingerprint analysis to evaluate the potential source(s) of petroleum hydrocarbons. According to SAIC's report: • The investigations) defined three affected areas of the Site, Area 1 (east), Area 2 (central), and Area 3 (west) which incorporates the onsite and adjacent offsite findings completed to date. The extent of affected soil/groundwater appears to continue offsite of Area 3 beyond the west boundary of the Site. Based on the field results, impacted soil/groundwater to the west, offsite is not a separate incident rather it appears to be contiguous with Site impacts associated with the historical pipelines. Future offsite investigations to the west of Area 3 will be addressed separately as a new site and called US Can-Offsite. • Fuel fingerprint evaluation results reported that the soil samples contained "moderately or extremely weathered" San Joaquin Valley crude oil. Trace amounts of"other hydrocarbons" suggested a second source unrelated to the historical crude oil pipelines. • Concentrations of total petroleum hydrocarbon as crude oil (TPHc) and polynuclear aromatic hydrocarbons (PAHs), exceeding applicable environmental screening levels, were detected in soil samples from depths between 5 to 80 feet bgs. The maximum vertical extent of affected soil is defined by non-detect (ND) for TPH compounds for a sample from an approximate depth of 82 feet bgs in soil boring (SB)-26. • Laterally to the south-southeast, the extent of TPH affected soil has been defined by Site investigation results and by similar investigations completed at Chevron's adjacent OVP/TAOC Vernalis Pump Station project. However, the lateral extent to the south- southwest and an area to the northwest have not been defined and additional characterization is needed. • Concentrations of TPH constituents in groundwater exceeding applicable environmental screening levels were detected and/or separate phase crude oil was reported at several boring locations. Vertically, the extent of TPH affected groundwater was defined by ND results for TPHd for a groundwater sample from a depth of approximately 82 feet bgs collected from boring SB-26. The lateral extent of TPH as diesel (TPHd) affected groundwater has not been defined. • Based on General Minerals analysis of the groundwater samples, results for total dissolved solids (TDS) exceeds the drinking water Secondary Maximum Contaminant Levels (MCLs) value of 1,000 milligrams per liter (mg/L). Other minerals, including boron, iron, manganese, chloride, and sulfate, among others exceeded respective water quality objectives (WQOs) for taste and odor. The uppermost groundwater will not likely be considered as a drinking water source.