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Geo(oguaC7ec& -Inc Page 5 <br /> site Ch!Ctert bon Report <br /> Valentine(Castle Motors) <br /> Project No 723 2 <br /> October a, 1999 <br /> .1 <br /> i <br />' • The sit exhibits a primarily clayey geology The clay is typically tan to brown and shows <br /> the presence of small amounts of fine-grained sand The clay ranges from plastic and soft <br /> to hard depending on moisture content <br /> 0 A sand and gravel layer is present at approximately 20 feet bgs <br />' + Hydrocarbon staining and gasoline odor was easily detectable down to approximately 70 <br /> feet bgs <br /> • A heaving, fine to medium grained sand was encountered dust below 70 feet This <br />' interval probably has a high flow of groundwater through it and hence washes the <br /> gasoline compounds away This is why heavy contamination was not observed below <br /> this unit <br /> See Appendix B, Boring Logs for more information <br />' 4.0 CONCLUSIONS AND RECOMMENDATIONS <br /> Based on our interpretation of the data collected over the course of this subsurface <br />' investigation, GTI have reached several conclusions These conclusions are based on the <br /> premise that the data we considered, although incomplete, are representative of actual site <br /> conditions We acknowledge that there may be undiscovered conditions, which would upon <br /> their consideration, change our interpretation and thus our conclusions <br /> Our recommendations are based on our knowledge of site conditions, and on the state and <br /> limitations of subsurface investigative technology <br /> lie 4.1 Conclusions <br /> Geological Technics Inc , taking into consideration the data obtained from this investigation <br />' and from the data compiled during previous soil and groundwater investigations and the <br /> regular groundwater monitoring events, makes the following conclusions <br />' 1 The site shows vertical extension of the soil and groundwater plume However, the <br /> SimulProbe data is inconclusive as to levels of BTEX & TPH-G at the deeper intervals <br /> due to the concerns mentioned above <br />' 2 The site geology is primarily clayey, which does not appear to be inhibiting migration of <br /> the soil or groundwater plumes <br /> 3 At this time the soil and groundwater plumes are not defined in any direction <br /> 4 The groundwater in the area of MW-2, MW-3 and MW-4 shows the highest <br />' concentrations of BTEX and TPH-G However, the other three wells show very high <br /> levels also <br /> 5 Groundwater at the site has shown the presence of DIPE and. TBA during past monitoring <br />' events <br /> 4.2 Recommendations <br />' GeoIogical Technics Inc makes the following recommendations based on the conclusions <br /> outlined above <br />' 1 Groundwater monitoring should occur for several quarters to determine the <br /> • concentrations of gasoline compounds in MW-101 before any decisions are made <br /> regarding further vertical investigation <br />