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Five hydrogeologic zones/unconsolidated soil horizons were <br /> identified from available monitoring well and soil boring data. <br /> F <br /> These five hydrogeologic:il layers comprise the setti'19 through <br /> which groundwater and hydrocarbon contaminants must migrate. The <br /> hydraulic characteristics of the soil horizons underlying the <br /> site are. an important understanding factor in <br /> p the potential fate <br /> Of subsurface on at the site,hydrocarbon contamination} � y The vadase <br /> zone, composed of zones Z, 2, e unsaturated <br /> t and the part of zona 3, <br /> is approximately 40 feet thick as observed <br /> during January 1968. <br /> A property wide hydrogeologic <br /> al summary relating the geologic ' <br /> zones to the hydraulic characteristics they exhibit at the sitea <br /> ; <br /> is presented in Table 2. The thickness of the <br /> vadose zone varies <br /> 3 - _ { <br /> due to seasonal variations in groundwater elevation. . <br /> t <br /> I� <br /> Selected samples were .collected from hydrogeologic zones 2, 3, and 4 <br /> during Du Pont" drilling. They were analyzed in the laboratory <br /> for grain size distribution, porosity,. and far'P�orizontal and <br /> - - - <br /> `'` � vertical permeability. A sumimary of .those results is listed in <br /> Table 4, and the details are given in Appendix D. <br /> a}e These. tests confirm the descriptions of the hydrogeologic soil ' <br /> horizons provided by t.he'field geologist. All three <br /> zone 2 <br /> samples were confirmed as silts ani clays of high <br /> } - -T_- Y _ g porosity and -- -- -- - <br /> low-verticnllpermeability. Sight samples from zone 3 were <br /> tested. Their <br /> grain size analysis results showed that the <br /> rimer sampled vary from silts to medium-co <br /> arse sands. The zone 3 <br /> sediments prove to vary both horizontally and vertically, <br /> as i. <br /> f <br /> MME <br /> r,. <br />