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4.0 INVESTIGATION RESULTS 'lJ The following sections summarize the results of the site investigation. All soil sample and temporary monitoring well locations discussed are shown on Figure 2. The results of the groundwater elevation measurements are 'D presented in Table 1 and shown on Figure 2. The analytical results for the soil samples are presented in Table 2 and Table 3 and the results of the reconnaissance groundwater samples are presented in Table 4. Chain-of- custody documents for all samples are included in Appendix B and Laboratory Analytical Reports are found in Appendix C. Soil analytical data was compared to USEPA Region IX industrial and residential Preliminary Remediation Goals (PBGs). Groundwater analytical data is compared to USEPA Region IX Tap Water PRGs and National Primary and Secondary Drinking Water Regulations (PMCLs and SMCLs). 4.1 SOIL CHARACTERIZATION 4.1.1 Surface Soil Analytical Data Three shallow borings were advanced through approximately six-inches of surface asphalt to approximately 1.5 feet bgs. Soil samples were collected between 6 inches and 1.5-feet and analyzed for TPH in the extractable and purgeable range as well as soil pH. Each of the surface soil samples (SS-1 through SS-3)had detectable concentrations of unknown hydrocarbons at concentrations of 3.5,320, and 10 milligrams per kilogram(mg/kg) respectively. There are no PRGs established for TPH in soil,and the Central Valley Regional Water Quality Control Board (RWQCB) has not established a cleanup goal for TPH. However,it is common practice for the Central Valley RWQCB to accept the cleanup goal of 100 mg/kg established by San Francisco RWQCB. Therefore, analytical results indicate a minor isolated impact to shallow soils at one 1 location, possibly associated with the asphalt or a minor oil leak from J heavy truck traffic. MI 8 LMC0/002430-3/3/2005 IJ