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i • <br /> b . 0 REMEDIATION SYSTEM DESIGN <br /> 6. 1 Air-Sparging and Vapor Extraction System (AS/VF,) Wells <br /> 6 1 1 Aar-Sparge Wells <br /> The proposed remediation system will incorporate the use of seven (7 ) <br /> air-sparge wells (Figures 7 and 8) One (1) air sparge well has already <br /> been installed at the site During the air sparging test conducted in <br /> August 2000, the air sparge radius of influence was shown to be at least <br /> 40-feet based on positive pressure tests and water table mounding <br /> measurements To be conservative, ASE is assuming an area of influence <br /> of 20-feet and recommending a spacing of 40-feet for air sparging wells <br /> across areas of the site with elevated hydrocarbon concentrations <br /> The wells will be drilled with a drill rig equipped with 8-inch diameter <br /> hollow-stem augers The wells will be constructed with 2-inch diameter, <br /> flush threaded, schedule 40, 0 020-inch factory slotted PVC well casing <br /> and blank casing The air-sparge wells will be screened between 17 a n d <br /> 19-feet bgs to allow for sparging at the bottom of the aquifer gust above <br /> the silty clay layer Blank casing will be installed above this screened <br /> interval Lonestar #2112 sand will be placed between the well casing and <br /> the boring from the bottom of the boring to 1-foot above the screened <br /> interval A 0 5-foot thick bentonite layer will be placed between the <br /> sandpack and the overlying cement sanitary seal A Portland cement <br /> sanitary seal will be placed above the bentonite layer to prevent surface <br /> water from infiltrating into the well The wellheads will be piped directly <br /> into an air-sparging manifold, which will then be piped directly to the air <br /> source (Figures 9 and 10) <br /> 6 1 2 Vapor-Extraction Wells <br /> The proposed remediation system will incorporate the use of seven (7 ) <br /> vapor-extraction wells During the dual-phase test conducted to August <br /> 2000, the vapor extraction radius of influence was shown to be at least <br /> 45-feet based on measurements collected during the dual-phase test To <br /> be conservative, ASE is assuming a vapor extraction influence of 20-feet <br /> and is proposing a spacing of 40-feet for vapor extraction wells across <br /> areas of the site with elevated hydrocarbon concentrations Based on this <br /> spacing, ASE proposes installing seven (7) vapor extraction wells (Figures <br /> 7 and 11) <br /> i <br /> Frank's One Stop Remedial Action Plan -- August 2001 <br /> -17- <br />