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Soil and Groundwater Investigation Report Catellus Property September 2006 Additionally,there are four wells that are more than one-quarter of a mile away and down gradient from the site. These wells are less of a concern because they are farther from the site and screened greater than 150 feet bgs. Four up-gradient water wells,all farther from the site than one-quarter of a mile,are not a concern. 6. CONCLUSIONS AND RECOMMENDATIONS Based on the results of this investigation, SAIC concludes the following regarding the nature and extent of affected soil and groundwater at the site: • Affected soil and groundwater identified during this investigation appear to originate from historic San Joaquin Valley crude oil of the overlying OVP(south of Byron Road). No affected soil or groundwater was found in the borings completed near the TAOC Pipeline(north of Byron Road),and no third-party sources near the affected areas were revealed by EDR's search of environmental records. However,no fuel fingerprint sample has yet been collected and analyzed to confirm the source. • Based on SAIC's research of DWR files,three water wells are of concern,due to their proximity to the site and shallow screened intervals(Figure 1 and Table 1,Map ID Nos. 15, 18,and 22). • Affected soil and groundwater is found in three plumes: o A North Plume,encompassing boring SB-1 and possibly affected groundwater from the Tracy Pump Station site; o A Central Plume,encompassing borings SB-5, SB-6, SB-8,and SB-9;and o A South Plume,encompassing borings SB-13 through SB-16 and SB-18 through SB-20. • The vertical extent of affected soil is delineated vertically at SB-1 of the North Plume at 25.5 feet bgs;at SB-8 of the Central Plume at 20.5 feet bgs; and at SB-15 of the South Plume at 21 feet bgs. However,affected soil of the South Plume is undefined at SB-20 at 21.5 feet bgs. • Although soil concentrations exceed the PRGs at borings SB-6, SB-15,and SB-20,the lateral extent of affected soil in these borings is defined by several encircling borings. Further,the affected soil of borings SB-6, SB-15,and SB-20 results from the transport of dissolved crude-oil constituents in flowing groundwater and should be further assessed in the future exclusively through groundwater investigation. • Affected vadose zone soil,which may be related to the OVP,exists near SB-8. Although the lateral extent of affected soil in SB-8 is defined by several encircling borings,benzene is present in the soil,and PAH concentrations are an order of magnitude above the PRGs. As a result, additional borings should be advanced around SB-8 to explore the nature and extent of affected soil and groundwater. • Up gradient of the OVP,the lateral extent of affected groundwater is undefined for the North, Central, and South plumes. • In certain areas down gradient of the OVP(and the TAOC Pipeline),the lateral extent of affected groundwater is undefined for the North,Central,and South plumes. In order to evaluate the whether the source of affected soil and groundwater identified during this investigation is historic San Joaquin Valley crude oil,or another petroleum substance, SAIC proposes to: • Collect and submit one soil or groundwater sample to Chevron Energy and Technology Company for a fingerprint analysis using gas chromatography/mass spectrometer(full-scan). From Science to Solutions-