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MAY Lb 195 11:45AM CLERRWRTER GROUP � <br /> CLEARW, ATER <br /> i Q u r, i N C <br /> The extremely low concentrations of O2 measured in vapor extraction and <br /> ' <br /> mer tanks indicate that the amount of vacuum <br /> monitoring wells neaz the for <br /> applied during the initial portion (first 4-B hours) will be low. Measurements <br /> taken in wells outside the contaminated zone indicate that 02 is available in the <br /> subsurface, and will move towards the extraction well over time. This vapor <br /> exchange will be enhanced by .the movement of atmospheric air to the <br /> subsurface, as the lot is not paved. <br /> It will be necessary, however, to allow,the vapor extraction equipment to operate <br /> fo'r several days, in order to optimize this air exchange. <br /> Given the concentrations of hydrocarbons measured in the subsurface, and the <br /> dela' onstrated lack of transmissivity, it,' is crucial that rigorous testing precede <br /> remedial. trade-off ana]yses. 1 believe that the test as plarumd will provide the most <br /> comprehensive .data set possible for future remedial alternative evaluation. <br /> Please. give me a call after you. have had a chance to review this information. I look <br /> forward to speaking with you again soon. <br /> Regards, <br /> learwater Group., Inc. <br /> Mark B. Ni,ebanck, . G. <br /> Operations.Manager <br /> i <br /> f cc. lits. 'Brooke Birkie, Neumiller & fieardslee <br /> i • <br />