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` %Pop w ATTORNEY-CLIENT PRIVILEGE groundwater chromatograms, it is apparent that there are similar constituents present in both background soil and groundwater. It is therefore likely that the chemicals in the groundwater from this round of sampling originate from background levels of chemicals in the soil and not from petroleum hydrocarbons at the Site. Another detect was found in the groundwater in the sampling round taken on May 19, 1993. Total extractable petroleum hydrocarbons were detected in SFW-3 at 64 µg/L (ppb). The chromatogram for this sample had the highest peaks at 9.50, 13.56, and 15.76 minutes (Figure 13). A standard using diesel was run in conjunction with the SFW-3 sample. The standard chromatogram had several peaks and the chromatogram did not appear to resemble that for the SFW-3 groundwater sample (Figure 14). Therefore, it is not likely that what was detected in the groundwater is diesel fuel. An analytical chemist (Craig Lee) at Sequoia Analytical (the company responsible for generating the chromatograms from the groundwater and soil samples from the Site), stated in a conversation on April 11, 1994 that the chromatograms represented by Figures 7 through and including 12 and Figure 14 do not resemble those obtained from fuel samples. Rather, it is more likely that the peaks represent some organic material in the soil such as rotting leaves. This analysis using chromatography of soil and groundwater samples demonstrates that the chemicals in the groundwater beneath the Site are not the same as the petroleum hydrocarbons in the Site soil, nor are the chemicals similar to diesel fuel. The chemicals detected in the groundwater are therefore not Site-related. Conclusions The purpose of this report is to demonstrate that the Santa Fe Railway Company Site in Stockton, California is suitable for closure. A risk assessment demonstrated that petroleum hydrocarbons in the soil at the Site will not impact the groundwater beneath the Site and do not pose a threat to either groundwater resources or human populations. Although hydrocarbons have been detected in the groundwater, analyses using chromatography of soil and groundwater samples have shown that it is not likely that these hydrocarbons are Site- related. In addition, it is not likely that Site-related chemicals in the soil would result in only random detections in the groundwater. The chemicals have been present for 60 years; it would therefore be expected that petroleum hydrocarbons would be detected on a regular rather than random basis. It is most likely that the hydrocarbons in the groundwater are from the native soil and represent background water quality in the area. Therefore the Site should be closed with the hydrocarbons left in place as they do not pose any significant risk to human health or the environment. GASTAFFVILMDELM.CLO 4