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06 April 2012 AGE-NC Project No. 95-0184 Page 5 of 7 3.1. SVE AND IN-SITU AIR SPARGING WELL NETWORK Vapor well VW-5 was drilled at an angle of 100 from vertical directed N 800 W, with a horizontal run of 9.7 feet, and was triple-completed as a vapor extraction remediapn well. Well VW-5A is screened frim 13 feet below surface grade (bsg) to 23 feet bsg, VW-5B from 26.5 to 41.5 feet bsg, and VW-5C fr�45 to 55 feet bsg; additionally, vapor well VW-26 is screened from 44 to 54 feet bsg. These final two well screens are proposed for active in-situ air sparging. 3.2. SOIL VAPOR EXTRACTION//N-SITU AIR SPARGING REMEDIATION Based on results of SVE remediation and limited IAS pilot test and in-well IAS performed at the site since December 2010 (utilizing soil vapor extraction well vacuum potential to agitate shallow ground water within well and thus potentially volatilize dissolved petroleum hydrocarbons like benzene), AGE proposes to operate a dedicated IAS system, which will increase the effectiveness of SVE by targeting both adsorbed and deeper dissolved hydrocarbons in the saturated zone located at approximately 35 feet bsg. The proposed IAS system will consist of an air compressor and a network of two-inch monitoring wells, which will be used to inject air beneath the ground water table, through pressurized wells. Based on historic and recent gro d w gr monitoring events performed at the site, depth to water generally ranges from' I: 'Irfeet bsg and seasonally fluctuates several feet during any given year. The successful remediation of the vadose zone is considered to be from near surface grade to approximately 30 feet bsg (water table).-AGE has determined this phase of remediation completed on the residual adsorbed hydrocarbons in the vadose zone, located from near 10 feet bsg and 30 feet bsg; as soil vapor extraction recovery samples have been non-detect for several events over the last two quarters. ...e_,T11i s vr�G*� R The IAS remediation proposed will be conducted by injecting air into a drowned deep, depth discrete remediation well near the soil vapor extraction wells exposed to the upper water table. The most compatible well for this air-sparge application would be well VW-5C, 4 screened 45 feet to 55 feet bsg and deep vapor well VW-2B screened 44 feet to 54 feet bsg. This work plan does not include the installation of sparging points; potentially, additional dedicated wells could be proposed instead of utilizing drowned soil vapor extraction wells. The injected air should volatilize dissolved hydrocarbons in the ground water, adsorbed petroleum hydrocarbons will be liberated and force hydrocarbon vapors into the vadose zone, where they can be withdrawn by the SVE system described above. Advanced GeoEnvironmental,Inc.