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1 <br /> I <br /> GROUND ZERO ANALYSIS, INC. <br /> I <br /> ' The amount of TPHg in the soil beneath the site is estimated to be <br /> 25, 000 pounds Based on the results of the test it is estimated <br /> that at startup of the VES, the flow rates and concentrations of <br /> ' gasoline vapors from wells VW-1, VW-2 , VW-3 , VW-4 , VW-5, and VW-6 <br /> would average approximately 40 cfm/well at 20, 000 mg/m3 This <br /> corresponds to a combined flow of approximately 250 cfm and an <br /> ' initial extraction rate of approximately 450 lbs/day Based on <br /> this .initial estimated extraction rate, cleanup of the site could <br /> be achieved in two months By the end of the second month of <br /> operation, however, based on Ground Zero' s experience at similar <br /> sites, the extracted TPHg vapor concentration may be expected to <br /> drop about 90°s The mass extraction rate will continue to decrease <br /> with time It is estimated that it will take at least six to eight <br /> ' months to reach the point at which mass removal has stabilized <br /> Calculated removal rates are presented in Attachment 4 <br /> Soil Vapor Extraction Test Concluaxons <br /> o The flowrates, applied vacuums and induced vacuums recorded <br /> during the VET suggest that the subsurface conditions are not <br /> homogeneous This is consistent with previous observations <br /> recorded during drilling of soil borings at the site <br /> o Soil vapor extraction appears to be feasible method of soil <br /> remediation at this site for gasoline hydrocarbons using wells <br /> VW-1, VW-3 , VW-4 , and VW-6 for higher permeability soil and <br /> ' wells VW-2 and VW-5 for lower permeability soil beneath the <br /> site <br /> ' o The effective radii of influence of the proposed vapor <br /> extraction wells averages approximately 30 feet and should <br /> sufficiently capture the extent of gasoline hydrocarbons in <br /> soil <br /> o Based on the laboratory analyses of the vapor samples <br /> collected during the VET, the average TPHg concentration at <br /> VES startup is estimated to be 20, 000 mg/m3 TPHg, which is a <br /> relatively high concentration <br /> o Should vapor extraction be instituted, the initial mass <br /> extraction rate for TPHg may be as high as 450 lbs/day This <br /> rate may decline as much as 9011 during the first three months <br /> of operation and then continue to decline It is estimated <br /> ' that using the proposed VES, mass removal will stabilize after <br /> approximately six to eight months of operation <br /> s <br /> h <br />