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' 08 April 2005 <br /> AGE-NC Project No 95-0173 <br />' Page 7 of 10 <br />' 3 4 3 Mass Calculation of Recovered Products <br /> The hydrocarbon mass removed during the SVE operating period was calculated using the equation <br /> IM= C•Q•t <br /> where M= cumulative mass recovered (kg) <br />' C =vapor concentration (kg/m3) <br /> Q =extraction flow rate (M3/hr) <br /> t= operational period, in hours <br />' Between 23 September and 22 December 2004 (fourth quarter 2004),the SVE unit operated a total <br /> of 2,160 hours (Table 6) The average analytical results (820 µg/1) of the influent SVE air flow <br />' samples (Table 5), average flow rates (approximately 74 cfm, Table 6) and the operational period <br /> (2,160 hours)were used to calculate the approximate mass of extracted gasoline during this period <br /> During the fourth quarter 2004 operational period, the mass of hydrocarbons extracted by the SVE <br /> system was calculated to be approximately 491 pounds,or equivalent to a volume of approximately <br />�. 79 gallons of gasoline Added to the estimated 2,014 gallons of hydrocarbons extracted from the <br /> SVE system since 11 April 2000 (start-up), the total volume of hydrocarbons extracted to date is <br /> estimated at 2,093 gallons (Table 7) A plot of the cumulative volume (gallons) of hydrocarbons <br /> extracted to date is included with Appendix F The volume/mass calculations for extracted <br /> hydrocarbons are included with Appendix G <br /> 4.0. CONCLUSIONS <br /> The implications from the December 2004 ground water monitoring event are as follows <br /> • Ground water flow direction was inferred to be east-northeast, at an approximate hydraulic <br />' gradient of 0 004 ft/ft Due to the generally low gradient at the site, slight variations in <br /> ground water measurements or changes of recharge/discharge of the local ground water could <br /> greatly modify ground water flow direction <br /> - vri average round water eleva.on at the site increased approximately 0 a0 feet between the <br /> s � <br /> 3'Quarter and 4'Quarter 2004 ground water monitoring events, however,since May 2000, <br /> I a steady trend of decreasing ground water elevations has been evident from 13 feet to 24 feet <br /> below mean sea level <br /> Ground water at the site was significantly above the screened intervals of wells AW-1 (A and <br /> B), AW-2 (A and B), and MW-13 (A-C), and slightly above the screened intervals of wells <br /> MW-1 through MW-4 The ground water elevation appeared to be within or near the <br /> i <br /> Advanced GeoEnvironmental,Inc <br /> i <br />