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SECTION 4 <br /> CONCLUSIONS <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 dnlling and trenching completed by 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 honzontally 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 /> aquifer is confined The groundwater flow direction, based on a <br /> three point solution is toward the north with a gradient of <br /> approximately 0 001 <br /> • Based on testing completed, diesel andr asoline fuels were <br /> ee <br /> detected in varying degrees in the sods 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 buned fuel tanks and <br /> restrained to a depth interval of 40 to 50 feet <br /> • The depth extent of affected sods 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 buned tanks Lateral <br /> migration of impacted groundwater has been toward the north - <br /> northwest and toward the west <br /> 41 <br />