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SECTION 5 <br /> Conclusions <br /> 5.1 Conclusions <br /> The purpose of this investigation was to provide additional site characterization of <br /> petroleum constituents in soil and groundwater beneath and downgradient of the Disco <br /> property to reduce uncertainty regarding the migration of contaminants from the site. The <br /> investigation was successful in assessing the horizontal and vertical extent of petroleum' <br /> hydrocarbons,EDB, and 1,2-DCA in soil and groundwater in the areas of concern. <br /> The CPT boring logs used in conjunction with cross-sections of the Disco property identify <br /> an apparently continuous sand unit approximately 5 to 10 feet thick,and located between <br /> approximately 90 to 110 feet below the former tank and pump area. The unit is thickest in <br /> the vicinity of MW-DIS-8S/8D and thins toward the south and east.The unit is not present <br /> in borings CPT-9,and-13.The geometry and extent of the sand unit in conjunction with the <br /> current groundwater flow direction provide insight to the migration characteristics of the <br /> constituents of concern. A fairly continuous fine-grained unit underlies the permeable zone <br /> in all CPT boring,and appears to be an effective barrier to vertical migration of compounds. <br /> Analytical results of soil and groundwater samples from this investigation indicate <br /> petroleum hydrocarbons,TBA,EDB,and 1,2-DCA are the primary constituents of concern <br /> for the Disco Site. These compounds are primarily located within the 5-to 10-foot thick <br /> sandy unit located about 90-to 100-feet below the site. The geometry,orientation,and extent <br /> of the hydrocarbon plume coincides with this permeable unit,and is consistent with the <br /> groundwater flow direction. <br /> The horizontal and vertical extent of 1,2-DCA is graphically shown on Figures 4 and 6 <br /> through 8. 1,2-DCA was detected in CPT-20 approximately 950 feet downgradient of the <br /> 4 site.1,2-DCA was not detected in monitoring well MW-DIS-12. The vertical extent of the <br /> contamination is predominantly confined to the sandy zone between 90 and 110 feet below <br /> ground surface. <br /> i <br /> c <br /> II <br /> 1 <br /> l <br /> f5FOiCPTMW REPORT KS_D00003670036 <br /> I <br />