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31 January 2013 <br />AGE-NC Project No. 02-0926 <br />Page 11 of 21 <br />3 gallons of gasoline. <br />Based on field parameters collected during the pilot test AGE concluded that dissolved <br />oxygen significantly increased at shallow well MW-5 and that the location and depth of well <br />MW-6 would provide adequate increases in dissolved oxygen, further promoting <br />remediation of the hydrocarbon-impacted groundwater plume. <br />Extended IAS Pilot Test <br />Between 16 March and 16 May 2012, an approximate 60-day extended IAS pilot test was <br />conducted at the site. The IAS pilot test was accomplished utilizing monitoring well MW-6 <br />(screened 70 to 75 feet bsg) as an active sparging point and pressured air (at 17 pounds <br />per square inch) supplied by an electric air compressor to inject air beneath the water <br />table, into the screen interval of the well. The on-site SVE system was utilized to recover <br />vapor from wells VW-1 and MW-5 throughout the duration of the pilot test. Based on <br />results from the pilot tests AGE concluded the following: <br />Dissolved oxygen (DO) measurements collected during the 72-hour pilot test <br />performed in December 2011 and the extended 60-day pilot test performed in <br />March and May 2012, significantly increased in shallow well MW-5. During both pilot <br />tests DO concentrations steadily increased within well MW-5 indicating that <br />communication between the sparge point and the impacted well was occurring. <br />Based on the results, monitoring well MW-6 should be used in the future to <br />remediate shallow zone dissolved hydrocarbon impact near well MW-5. Additional <br />shallow screened air sparge wells would be warranted to expedite the remedial <br />efforts in shallow zone water should full scale air sparging commence at the site; <br />Influent vapor stream concentrations significantly increased during the 60-day pilot <br />test as compared to results from the 72-hour pilot test, which could likely be <br />attributed to use of MW-5 as a vapor recovery well. AGE further concluded that <br />additional vapor recovery wells would be warranted in the vicinity of MW-5 should <br />full scale implementation of IAS commence at the site; <br />Deeper air sparging liberated residual "drowned" adsorbed hydrocarbon impacted <br />soil in the area surrounding MW-5 and MW-6. TPH-g concentrations were detected <br />at concentrations as great as 1,200,000 pg/I, the highest dissolved concentrations <br />reported historically for the site. However, based on samples collected during the <br />June monthly pilot test sampling, BTEX concentrations surrounding well MW-5 were <br />significantly reduced (up to 90%) as a result of the extended pilot study; <br />Based on vapor samples collected during the testing period, a significant <br />hydrocarbon mass was removed (1,045.7 pounds/167.4 gallons) as a result of pilot <br />sparging and vapor extraction performed near well MW-5. <br />Advanced GeoEnvironmental, Inc.