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re 15 April 1996 ' AGE-NC Project No 95-0121 Page 3 of 9 ' 3.0. SCOPE OF WORK ' AGE proposes to initiate an iii-situ vapor extraction (SVE) system combined with in-situ air sparging (IAS) In order to maximize the efficiency of the treatment, a 24-hour operation of the system is planned , A typical destruction rate of greater than 95% of hydrocarbon vapors is expected throughout the entire cleanup duration r ' 3 1 s SOIL VAPOR EXTRACTION SYSTEM DESIGN It is proposed that the recovered hydrocarbon vapor undergo a thermal destruction process , The ' proposed unit is a direct fired thermal oxidizer SVE system A typical diagram of the system is illustrated in Figure 3 'Proposed Vapor Evtraction System The SVE system is connected through a manifold box to the vapor recovery wells and should be able to operate at between 225 and 250 cubic feet per minute (cfm) The thermal oxidizer can be outfitted with a catalytic module and/or a heat exchanger to provide an eflective destruction ratio at reduced concentrations of hydrocarbon vapor The vapor will be extracted from a configuration of extraction wells using a vacuum blower and routed to the thermal oxidizer ,-Supplemental fuel (i e , natural gas) will be added to maintain the optimal temperature for a maximum destruction rate of hydrocarbon vapors Additional information on the proposed system is included with Appendix A 3 1 1 SOIL VAPOR EXTRACTION WELL INSTALLATION < RS AGE proposes to install nine SVE wells utilizing a truck mounted, hollow stem drill rig and 8-inch _ hollow stem augers SVE well locations are depicted in Figure 4 -Proposed Sorl I%apoi Er1raction Well Locations Soil borings will be advanced to depths of apps oximately 25 feet All hollow stem augers will be steam-cleaned prior to advancement in each borehole Cuttings and rinseate generated during drilling activities will be containerized in properly labeled D O T model 17H 55-gallon drums, and stored on-site in an area inaccessible to the general public _ Soil borings will be completed as 2-inch diameter SVE wells using PVC casing A proposed SVE well construction diagram is included as Figures 5 -Pi oposed Soil Vapor Exti action Well Design A PVC well casing will be emplaced through the hollow stem of the augers, and incrementally raised as a#3 Lonestar Lapis Luster sand is slowly poured down the annulus between the well casing and the inner wall of the hollow stem auger The filter pack will be placed adjacent to a screen (0 020 inch screen size)'from the bottom of the screen to a point approximately 2 foot above the,top of the screen An approximate five-foot seal of bentonite chips will be placed above the filter pack and hydrated with clean tap water All SVE wells will be sealed with a grout All extraction wells will be screened throughout the entire depth of contamination However, individual screen intervals will be 1 s 1 1 +