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19 October 2012 <br /> AGE-NC Project No. 97-0312 <br /> r <br /> Page 19 of 22 <br /> 7.3. RESULTS OF EXTENDED HVSVE PILOT TEST <br /> The HVSVE pilot test was operated at the site over a five-day period, for approximately <br /> 92.8 hours. <br /> Initially, the HVSVE operated at normal conditions at approximately 10 inches of mercury. <br /> However, following one day of operation of vacuum extraction, the catalytic oxidizer began <br /> a endothermic reaction, which resulted in overheating from the fuel within the soil vapor <br /> giving off greater heat than could be dissipated through advective flow of soil vapor. From <br /> the well VW 1 location, the flow rate was measured to be between 45 and 100 SCFM at the <br /> start of the test when 8 to 10 inches of mercury was applied. The flow rate was nearly <br /> 100 SCFM when the HVSVE equilibrated, yet over time the catalytic oxidizer overheated <br /> at a vacuum of 7 inches of mercury. During the time of overheating, the average flow rate <br /> over the pilot test was 65 SCFM. However, the maximum flow rate would have been <br /> maintained if not for the overheating of the catalytic oxidation chamber and cell. <br /> The greatest OVM readings ranged from 2,600 to 3,760 ppmv. The induced vacuum <br /> extracted vapor from well VW-1 was over 100 IOW during operation. <br /> From the surrounding observation wells, the greatest induced vacuum measurement was <br /> observed at vapor point VP-1 at well MW-5. The vacuum measured at well VP-1 ranged <br /> from 0.9 IOW to 3 IOW. The vacuum measured at vapor extraction well VW-2 (located 40 <br /> feet west of VW-1) as high as 1.45 IOW and an induced vacuum was generally observed <br /> in well VW-3 (located 30 feet east of VW-1), measurements as high as 1.75 IOW. <br /> The maximum vacuum measured at wells VP-1,VW-2,VW-3 during the HVSVE pilot tests <br /> were plotted versus the distance from the extraction well. The effective radius of influence <br /> was determined by generating a linear, best-fit line through the shallow soil vapor well data <br /> points to correlate distance to vacuum data. Based on the United States Environmental <br /> Protection Agency (EPA)-prepared document, How to Evaluate Alternative Cleanup <br /> Technologies For UST sites, the radius of influence is considered to be the distance from <br /> the extraction well at which a vacuum of at least 0.1 inches of water is observed. Based <br /> upon an effective vacuum potential of 0.1 inches of water, the calculated effective radius <br /> of influence at the site is approximately 50 feet for the first pilot test and well beyond 125 <br /> to 150 feet following the multi-day test. Based on the fine grained soil type a conservative <br /> soil vapor remediation radius was justified and anticipated. <br /> I✓ <br /> 7.4. ANALYTICAL RESULTS OF EXTENDED HVSVE SOIL-VAPOR SAMPLES <br /> TPH-g was detected in the soil-vapor samples at concentrations ranging from 7,700 pg/I <br /> to 26,000 pg/l. Benzene, toluene, ethylbenzene and total xylenes were detected in the soil- <br /> vapor samples at concentrations as high as 210 pg/I benzene, 630 pg/I toluene, 790 pg/I <br /> Advanced CeoEnvironmental,Inc. <br /> v <br />