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17 October 2000 <br /> AGE-NC Project No. 98-0450 <br /> Page 6 oC7 <br /> 3.2. MASS OF RECOVERED IIYDROCARBONS <br /> — The hydrocarbon mass (TPH-g) renioved during the operating period was calculated usinso the <br /> following equation: M — C•Q•t ` <br /> where: M = cultullative mass recovered (k(,) <br /> C = soil-vapor concentration (kg/m') <br /> Q = extraction flow rate; (m-7hr) <br /> t = operational period. in hours <br /> — The operational time was divided into three time periods. Mass of hydrocarbons removed was based <br /> on analysis of soil-vapor samples. The mass of extracted hydrocarbons was calculated for each time <br /> period using average hydrocarbon concentrations of influent soil-vapor sample data and av erage air <br /> flow rates. <br /> Approximately 1,070 gallons of hydrocarbons as gasoline were extracted and destroyed from SVE <br /> network at the site between 17 ,luly and 26 September 2000. The volume/mass calculations are <br /> attached in Appendix C. <br /> �.;. 1;1'-,SIT(;1AIR SPARGING <br /> elevated concentrations ofdissolved oxygcn were detected in monitoring wells BMW-3, BMW-4. <br /> BMW-5 and MW-5. which were used as observation wells within and outside the IAS network on <br /> the site. <br /> Dissolved oxygen concentrations remained or decreased below pre-remedial levels in well BMIAL I <br /> — and BMW-2. Sparging rates were measured at approximately 8 to 10 scfm during each monitorinl <br /> event. A pressure of approximately 10 psi was maintained for the air sparging flow- rate. <br /> 4.0. SUMMARY AND CONCLUSIONS <br /> — Based on the data collected during this phase of'site remediation, AGE finds: <br /> • Results from previous assessment investigations showed that the highest concentrations of <br /> petroleum hydrocarbons in soil were near the northern portion of the site at depth intervals <br /> of 15 to 40 feet bsg. Lower concentrations of hydrocarbons were detected in borings around <br /> the southeast portion of the site (VW-1 and VW-2_ BMW2 and SB7) at depths between 15 <br /> and 40 feet bsg, corresponding to the interval of historical ground water level fluctuations. <br /> — I dsvruced(.:cul:m irunmrnt;il,l nc. <br />