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a <br /> 1766 MONTE DIABLO AVENUE <br /> September 2 1994 <br /> Page 2 <br /> Task 2: Install Vapor Extraction Well(s), Air Sparging Wells) and <br /> Vapor Extraction and Air Sparging Observation Wells <br /> { <br /> One 4-inch-diameter Schedule 40 PVC vapor extraction well (VEW), one 2-inch- <br /> diameter air sparging well (ASW), two vapor extraction observation wells and three <br /> air sparging observation wells should be installed. In order to reduce drilling costs, <br /> -.--,Tthe:vapor_extraction!air-i.spargingobser-_vatien:wells-could:be installed-,in-!the san-►ems.=---�. <br /> boring (nested well configuration or dual completion). The observation wells should <br /> be installed at increasing distances and different directions from the VEW and ASW, <br /> The screened interval of the air sparging well should be at a minimum depth of 10 <br /> feet below tete water table, The air sparging observation well should be screened at <br /> least 5 feet below ground water and approximately S feet above ground water, The <br /> vapor extraction well and observation wells should be screened just above the water <br /> table. <br /> F <br /> Task 3; ' Perform an Air Sparginffapor Extraction Feasibility Study <br /> • 3 <br /> The purpose of the combined soil vapor extraction/air sparging feasibility test is to <br /> determine the effective radius of influence of air sparging and vapor extraction and <br />` estimate the number and placement of alar sparging points and vapor extraction wells. k <br /> During the test, vacuum pressures, vacuum flow rates, air injection pressures and <br /> E rates, and water levels should be measured. Soil vapor samples and ground water <br /> samples should be collected and analyzed for total petroleum hydrocarbons (TPH) as <br /> gasoline and benzene, toluene, ethylbenzene, and total xylenes (BTEX). Baseline <br /> levels should be determined before starting, including water table levels, <br /> concentrations of TPH as gasoline and BTEX in ground water and soil vapor, E <br /> dissolved oxygen in the ground water. <br /> �+ r <br /> E <br /> WALLACE+KtJHL <br /> fir ASSOCIATES INC, <br />