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' 12 February 2002 <br /> • AGE-NC Project No. 98-0450 <br /> Page 5 of 6 <br /> ' 3.4. MASS OF RECOVERED HYDROCARBONS <br /> The hydrocarbon mass (TPH-g) removed during the operating period was calculated using the <br /> following equation: M = C•Q•t <br /> where: M= cumulative mass recovered (kg) <br /> ' C = soil-vapor concentration (kg/m 3) <br /> Q= extraction flow rate (m3/hr) <br /> t=operational period, in hours <br /> ' The operational time was divided into four 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 average air <br /> flow rates. <br />' Approximately 114 gallons of hydrocarbons as gasoline(TPH-g)were extracted and treated by the <br /> SVE system, at the site between 09 August and 12 December 2001. The volume/mass calculations <br /> are attached in Appendix C. <br />' 4.0. DISCUSSION AND CONCLUSIONS <br /> Based on the data collected during this monitoring period, AGE concludes: <br /> • Ground water on the site was flowing toward the south from the former UST area. The <br /> ground water table is nearly flat with a hydraulic gradient of approximately 0.007 feet/feet. <br />' • The greatest concentration of dissolved hydrocarbons continues to be in the area of well <br /> BMW-4 located in the area of the former UST location. TPH concentrations have remained <br />' at significant levels(+5,000µg/1),while BTEX compounds concentrations have declined in <br /> the area of the former USTs (BMW-4) and in the down gradient direction (MW-5). <br /> • MTBE was detected in two of the six samples at concentrations as high as 220 gg/1 in sample <br /> MW-5, at the southern edge of the site. <br /> Based on SVE remediation data collected between August and December 2001, AGE,concludes: <br /> • The volume of hydrocarbons extracted by the SVE system was calculated to be <br />' approximately 114 gallons of petroleum hydrocarbons (Appendix C) during the third and <br /> fourth quarters 2001 monitoring period. <br />'•' • Since initiation of the SVE system,the total volume of petroleum hydrocarbons:extracted is <br /> Advanced GeoEnviron mental,Inc. <br />