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3) Groundwater is contaminated in both borings, but concentrations are somewhat higher <br /> S near the building than they are near the dispensers MTBE and 1,2-DCA are exceptions to <br /> this generalization, the MTBE concentration in the dispenser boring was higher by two <br /> orders of magnitude, and the 1,2-DCA concentration was the same in both borings The <br /> distribution of the various groundwater contaminants is not understood at the present <br /> time <br /> 4) Groundwater is partially confined at the site by the clayey paleosol (Unit 5) that is <br /> present from about 18 to 25 feet The thickness and permeability of this layer are <br /> probably insufficient to form a good aquitard, but the fact that this unit was somewhat <br /> drier than overlying and underlying units when it was sampled, coupled with the fact that <br /> groundwater was initially penetrated at a depth of nearly 35 feet but later rose to a depth <br /> of 27 feet indicates that there is some restriction to upward flow The fine-to-medium- <br /> grained sand below 25 feet (Unit 7) has the characteristics of an aquifer rather than a <br /> confining layer, and is probably not the retarding layer <br /> 5) Lead is not a contaminant of concern at this site <br /> 6) In the past, diesel was not suspected to be a potential contaminant at this site, and <br /> samples were not analyzed for such longer-chain hydrocarbons Neither the source of this <br /> contaminant nor its migration path to groundwater has been identified <br /> 6 <br />