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INC <br /> 6.2 Concrete Tank Area <br /> The concrete tank area was investigated by WZI using previous TMG (1992) data to <br /> determine the subsurface extent and nature of soil known to have been impacted by <br /> hydrocarbon compounds leaking from the tank or from surface spillage All work <br /> conducted was done in accordance with the workplan approved by SJCLHD (WZI, 1993) <br /> Two vertical borings and one angle boring were placed adjacent to and under the <br /> concrete tank (Exhibit 8) Soil borings were advanced in the subsurface and sampled <br /> using sampling protocols outlined in Appendix III Individual boring logs are depicted in <br /> Appendix IV Analytical laboratory results from the soil samples obtained in these borings <br /> are depicted in Appendix V <br /> Exhibit 9 depicts a composite geologic column for the Concrete Tank area based on WZI <br /> and TMG soil boring logs Individual logs and the composite log indicate that the upper <br /> 55 feet of the subsurface is primarily silty sand with alternating, interbedded fine to <br /> Smedium-grained sand and silty clay These sediments are consistent with an alluvial/ <br /> lacustrine depositional environment that is present in the upper 1,000 feet of northern San <br /> Joaquin County (Page, 1986) <br /> Exhibits 10, 11, and 12 depict three cross-sectional views through the Concrete Tank area <br /> based on the previous and new soil borings Analytical laboratory data from the samples <br /> are plotted on each of the depicted soil borings in the correct subsurface location <br /> Hydrocarbon impacted soil is present in the subsurface immediately surrounding the <br /> concrete tank to an estimated maximum distance of approximately five feet Hydrocarbon <br /> concentrations in the soil range as follow <br /> i <br /> s <br /> 17270010 013 Page 19 <br />