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SECTION 4 <br /> CONCL USI DNS <br /> This section briefly summarizes the soil and groundwater conditions <br /> beneath the site and extent of petroleum hydrocarbon occurrence in <br /> soil and groundwater beneath the site. <br /> • Based on exploratory drilling and trenching completed Eby ERM- <br /> West, Inc., the site is underlain by unconsolidated to semi- <br /> consolidated sands and clays to a depth of at least 50 feet. <br /> Identifiable soil units were identified and the generalized strata, <br /> from the surface downward, consist of a brown clay, <br /> approximately 25 Feet in thickness, a tan sand approximately 10 <br /> feet in thickness, a grey clay approximately 10 feet thick, a grey <br /> sand approximately 5 to 10 feet in thickness, and a lower grey clay <br /> of unknown thickness. The units are horizontally bedded and <br /> laterally heterogeneous. <br /> • Groundwater was encountered in the grey sand unit <br /> Measurement of water levels MPW-1 to MPW-3 indicate that the <br /> aw aquifer is confined The groundwater flow direction, based on a <br /> three -point solution is toward the north with a gradient of <br /> f approximately 0 001. <br /> • Based on testing completed, diesel and gasoline fuels were <br /> detected in varying degrees in the soils and groundwater <br /> underlying the site. <br /> • The lateral extent of affected soils appears to be limited to an area <br /> centered on the former location of the buried fuel tanks and <br /> restrained to a depth interval of 40 to 50 feet <br /> r The depth extent of affected soils appears to be limited to <br /> approximately 50 feet based on the dense nature and therefore <br /> likely low permeability of the lower grey clay unit. <br /> • Groundwater impacted by diesel and gasoline fuels generally <br /> surrounds the former location of the buried tanks. Lateral <br /> migration of impacted groundwater has been toward the north - <br /> northwest and toward the west. <br /> i <br /> 4-1 <br /> l <br />