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Mr. Soon Kim <br /> Page 11 <br /> August 11, 1995 <br /> 102429.AS.T8 <br /> vacuum influence make it difficult to provide a precise radius of influence. Differential <br /> pressure data is attached for NP-2. <br /> The radius of influence for air sparging wells can be either considered the groundwater <br /> surface area where groundwater stripping is significant or the volume of groundwater that <br /> shows a significant increase in dissolved oxygen concentration. Stripping is difficult to <br /> measure due to the preferential pathway migration of sparging air, and the complexity of the <br /> many physical chemistry processes that influence the equilibrium vapor concentration in the <br /> smear zone. Dissolved oxygen concentrations measured on 5125195 in piezometer NP-1 at 80 <br /> feet and 90 feet bgs were 6.5 and 6.1 mg/L respectively just after AS/SVE system shutdown. <br /> A typical dissolved oxygen concentration that is rate limiting for biological degradation is 2.0 <br /> mg/L. NP-1 is 10 feet from AS/SVE-1 and 17 feet from AS/SVE-1, so we know the air <br /> sparging radius of influence is at least greater than 10 feet and it could be as large as 25 feet <br /> or more. Dissolved oxygen, concentration is provided as the fust data point in the <br /> groundwater respiration rate test data(see attachments). <br /> Estimated Mass Removal by SVE <br /> Based on the assumption that gasoline has an average molecular weight of 120 grams/mole, <br /> the calculated AS/SVE system gasoline removal to date is 6,800 pounds, or approximately <br /> 1,100 gallons (specific gravity of gasoline is 0.74). Table 3 presents measured data, from the <br /> system operations log, considered in the estimate of cumulative gasoline removal. Cumulative <br /> gasoline removal is expected to continue to taper off logarithmically, as shown in Figure 3. <br />