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J <br /> 8 August 2000 <br />. AGE-NC Project No 95-0143 <br /> Page 7 of 8 <br /> Field measurements of flow, vacuum and organic vapor concentration in the air streamfrom each <br /> extraction well were measured on a periodic basis Due to the tight soil conditions and limited screen <br /> interval, a vacuum potential near 50 inches of water was maintained on wells VW1,V W2,VW3 and <br /> VW5 in order to achieve minimal flow from these wells Organic vapor was measured at <br /> concentrations as high as 716 ppm in the extracted air streams (VW5) <br /> 3 6 ANALYTICAL RESULTS OF SOIL VAPOR SAMPLES <br /> TPH-g was detected in the soil vapor samples at concentrations of 520 µg/l to 490 µg/l A slight <br /> increase in hydrocarbon concentrations (5 10 µg/1 to 520 µg/l TPH-g) was detected during the 12 <br /> April 2000 monitoring event However, hydrocarbon concentrations decreased during each <br /> subsequent sampling event Analytical results are summarized on Table 6 The laboratory reports <br /> (MAI sample Nos 34617, 34618, 35854, 35855, 38786, 38787, 39841 and 39842) and chain-of- <br /> custody forms are Included in Appendix E <br /> 3 7 MASS OF HYDROCARBONS REMOVED <br /> A total of approximately 505,170 cubic feet of soil vapor was extracted from the site between 01 <br /> April 2000 and 30 June 2000 Approximately 249 kilograms, or 89 gallons, of gasoline were <br /> removed from the site between 01 April 2000 and 30 June 2000 Calculations for the mass of <br /> hydrocarbons removed are included in Appendix F <br /> 4.0. SUMMARY/CONCLUSIONS <br /> Based upon data collected from the site, AGE concludes <br /> • Ground water elevation decreased approximately 0 86 feet between February 2000 and May <br /> 2000 The Inferred ground water flow direction remains toward the north to northeast at the <br /> site <br /> • Petroleum hydrocarbons were detected in six of the nine wells sampled at concentrations <br /> ranging from 250 µg/1 (MW-7)to 200,000 µg11 (MW-3) Measurable free product was not <br /> encountered during the May 2000 monitoring event Fuel oxygenates were not detected in <br /> ground water samples collected during the May 2000 monitoring event <br /> • Ground water mounding is apparently occurring within two of the vapor extraction wells <br /> However, the lateral extent is very limited and ground water levels return to normal upon <br /> Interruption of vapor extraction The ground water mounding appears to be caused by vapor <br />• Advanced GeoEnvironment"Inc <br />