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Tri-Regional Board Recommendations for soil impacted by diesel hydrocarbons Results of <br /> these analyses are discussed in Section 4 2 of this report <br /> 4.0 Site Investigation Result <br /> Observations and chemical data collected during this investigation are discussed in this section <br /> ' 4.1 Geology and Hydrogeology <br /> In general, the site geology consists of fine-grained Quaternary alluvial deposits composed of <br /> tinterbedded silts, silty clays, and minor sands Groundwater was not encountered during the <br /> investigation and is estimated to occur at 45-50 feet bgs <br /> 4.2 Petroleum Hydrocarbon Distribution <br /> ' Fourteen soil samples were collected from two remaining areas of concern at the former UST <br /> area during this investigation All samples were analyzed for TPH-diesel and BTEX by a State <br /> ' of California certified analytical laboratory None of the samples collected exhibited <br /> concentrations of TPH-diesel or BTEX above the method detection limit The results of the soil <br /> sampling activities indicate that there are no remaining TPH-diesel impacted soils in the former <br /> UST area Analytical results are summarized on Table 1 and Figure 3 The laboratory report, <br /> including method reporting limits, is provided in Appendix C <br /> ' 5.0 Conclusions and Recommendations . <br /> This section presents the conclusions and recommendations of this investigation <br /> 5.1 Conclusions <br /> This environmental investigation included the drilling and sampling of four Geoprobe locations <br /> ' in the two remaining ADCs in the former UST area Samples were obtained at five foot intervals <br /> to a depth of 25 feet and were analyzed for TPH-diesel and BTEX None of the soil samples <br /> collected exhibited concentrations of either parameter above the method reporting limit <br /> ' Groundwater was not encountered above a depth of 35 feet bgs during this investigation Based <br /> on observations at an adjacent site and information from the San Joaquin County PHS/EHD <br /> representative, groundwater in the area is expected to occur at approximately 45 to 50 feet bgs <br /> ' SAC/08-29-97/ENG/771744 6 <br /> 1 I <br />