ARCHIVED REPORTS XR0012684 - Laserfiche WebLink

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MT FEW F, n - rr mi f SEC`1?ION 4 CONCLUSIONS This section briefly summarizes the soil and groundwater conditions beneath the site and extent of petroleum hydrocarbon occurrence in soil and groundwater baneath the site. • Based on exploratory drilling and trenching completediby ERM- West, Inc., the site is underlain by unconsolidated to semi- consolidated sands and clays to a depth of at least 50 feet. Identifiable soil units were identified and the generalized strata, from the surface downward, consist of a brown clay, approximately 25 feet in tl-ackness, a tan sand approximately 10 feet in thickness, a grey clay approximately 10 feet thick, a grey sand approximately 5 to 10 feet iu tlAckness, and a lower grey clay ' of unknown thickness. The units are horizontally bedded and laterally heterogeneous. • Groundwater was encountered in the grey sand unit. Measurement of water levels MPW-1 to ii+IPW-3 indicate that the aquifer is confined. The groundwater flow direction, based on a three point solution is toward the north with a gradient of approximately 0.001. • Based on testing completed, diesel and gasoline fuels were detected in varying degrees in the soils and groundwater uibderlying the site. The lateral extent of affected soils appears to be limited to an area : centered on the former location of the buried fuel tanks and restrained to a depth interval of 40 to 50 feet. • The depth extent of affected soils appears to be limited to approximately 50 feet based on the dense nature and therefore Iikely low permeability of the lower grey clay unit;. • Groundwater impacted by diesel and gasoline fuels generally surrounds the former location of the buried tanks. Lateral migration of impacted gro mdwater has been toward the north - northwest and toward the west. - 4-1 i i