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13 September 2001 <br /> AGE-NC Project No. 98-0450 <br /> Page 5 of 6 <br />' was not established from the PID field measurements. Operational field measurements of the SVE <br /> unit are summarized in Table 5. <br />' Hydrocarbon concentrations (TPH-g) detected in influent soil-vapor samples were as high as <br /> 1,768,ug/l.The laboratory reports(AAL and MAT Sample Numbers: 264778,264779,70560,70561, <br /> 72764, 72765, 74498 and 74499) Quality Assurance and Quality Control (QA/QC) reports and <br /> chain-of-custody forms are included in Appendix C. <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') <br /> Q= extraction flow rate (m'/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 347 gallons of hydrocarbons as gasoline (TPH-g) were extracted and treated by the <br /> SVE system, at the site between May and July 2001. The volume/mass calculations are attached in <br /> 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-southwest from the former UST area. <br /> The ground water table is nearly flat with a hydraulic gradient of approximately 0.005 <br /> 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 (- 10,000 ug/1), while BTEX compounds concentrations have declined <br /> in the area of the former USTs (BMW-4) and in the down gradient direction(MW-5). <br /> Advanced GeoEnvironmental,Inc. <br />