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of � <br /> ti <br /> below ground surfaces (bgs), in MW-6 and B-5, respectively. Minor <br /> amounts of hydrocarbon were detected at 20 feet bgs in B-2, 50 feet <br /> west of MW-I (Figure 4). <br /> • Soil contamination by hydrocarbon constituents appears to be limited <br /> to a relatively small area within the immediate vicinity of the tank <br /> excavation pit area. <br /> Vertical migration of contaminants seems to be limited away from the tank <br /> Pit due to the prvoence of a very stiff silty clay. Lateral migration possibly <br /> - takes place along lenses of higher permeability silts and sands. Such sand <br /> lenses (0,10 inches thick) were observed in tha 15.0 foot sample in B-5. These <br /> leasas are interpretel a be discontinuous and may rot be present in all areas <br /> under the site, s3-],'-dp ;�oximately 50 feet north of MW-I encountered several <br /> thin sand lenses which were not contaminated. It is thought that these sands <br /> Are not continuous laterally to the -tank pit. <br /> 6.2 GROUiTiDt?ATBR CONTAMINATION <br /> • <br /> Grounds-.7-ter contamination by hydrocarbon constituents and chlorinated <br /> h- solvents appears to be limited to the area of the former tank <br /> excavations (Figure 4). Water samples from the Phase II wells, MW- <br /> „„ 5 and MW-6, had no detectable levels of contaminants, though both <br /> L, <br /> wells are downgradient to MW-1. <br /> Free-product appears limited to the immediate area around MW-l. <br /> Product baildown testing in MW-1 indicates the order of one-inch of <br /> product thickness in groundwater. <br /> �- Aquifer testing of wells MW-3, MW-4, MW-5, and MW-6 suggest that <br /> aquifer materials are heterogeneous with hydraulic conductivities <br /> indicative of silts up to silty sands or very fine sands. <br /> SAC03.0C1 9 November 1989 <br />