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I <br />i <br />I <br />I <br /> <br />F. Site Hydrogeolo~ <br /> <br />The mention of the till acting as an aquitard on p. D-54 should be qualified. As <br />mentioned previously, the competency of the till layer has not been completely <br />defined. <br /> <br />On p. D-66 it states that a hydraulic connection appears to exist between the buried <br />outwash and the overlying till. This in turn would infer that the overlying upper <br />sand unit would also be connected. <br /> <br />G. Summary <br /> <br />The report cannot seem to agree internally with the degree of protection provided <br />by the intermediate till layer. <br /> <br />The report mentions but does not use the existing groundwater quality database for <br />the area in developing the hydrogeological interpretation. The groundwater quality <br />data is an invaluable took in plume mapping, dispersion, flow directions, etc. The <br />addressing of groundwater quality was required in the Scoping Decision. <br /> <br />The ability to monitor groundwater at the site considering the proximity of the <br />existing hazardous waste disposal area seems to be over-optimistic. <br /> <br />The feasibility of and reliance upon a slur~ wall keyed into an admittedly leaky <br />aquitard to separate the existing Oak Grove Landfill and Site D does not seem to <br />be highly reliable. <br /> <br />Reined,at,on methods to be used at Site D would depend upon remediation <br />activities at the Oak Grove Landfill. Currently, however, there have been no <br />proven remediation methods employed at the Oak Grove Landfill site. <br /> <br />11 <br /> <br /> <br />