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' Harding Lawson Associates <br /> ' IV SITE CHEMICAL DISTRIBUTION <br /> A. Soils <br /> Soil samples were taken from Wells 13, 15, 16 and 17 at the time of <br /> installation by Groundwater Technology. These samples were analyzed for volatile <br /> hydrocarbons, benzene, toluene, and xylene. The results of these analyses are <br /> shown on Plates 3 through 5. <br /> Wells 13, 16, and 17 (Plates 3 and 4) show a trend of decreasing chemical <br /> concentrations with depth, except for an increase of benzene with depth in Well 17. <br /> Well 15 (Plate 5) shows a decrease of chemical concentration with depth within the <br /> vadose zone, but these chemical concentrations increase once within the saturated <br /> 1 zone. <br /> ' The highest concentrations were detected in soils at Well 16. These <br /> concentrations appear to be localized, as evidenced by the chemical concentrations <br /> of much less magnitude measured in Wells 15 and 17, approximately 105 and <br /> 90 feet, respectively, from Well 16. The soil samples in Well 16 were taken from <br /> ' the silty sand unit rather than the silty clay unit. This unit is discontinuous; it <br /> ' does not appear in Well 17, but a small portion of it was encountered in Well 15. <br /> However, high concentrations similar to those detected in the sand unit in Well 16 <br /> ' are not observed in the sand unit in Well 15. These soil sampling data, however, <br /> are insufficient to characterize the distribution of chemical concentrations In soil <br /> ' on the site. <br /> The drilling logs (Appendix A) indicate that hydrocarbon odors were <br /> detected during drilling. Although the depth to which odors were detected was not <br /> ' noted, odors were detected in Wells 1, 8, 10, 11, 13, 15, 16 and 17. Most of these <br /> 1 <br /> November 24, 1987 6 of 9 <br /> ' B2203-R <br />