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event that the soil vapor flow rate from the soil formation surrounding the <br /> dual phase extraction well screened interval is insufficient to entrain <br /> ground water in a turbulent condition, atmospheric air can be bled into <br /> the extraction well annulus at the air bleed valve, as shown in <br /> Drawing M-2. <br /> For extraction at the site, a 1-inch extraction tube, supplied with 20 inches <br /> mercury (Hg) applied vacuum will be utilized. Under this arrangement, <br /> the estimated liquid and vapor velocity in the extraction tube is <br /> approximately 2,500 feet per minute. This high velocity of extraction, the <br /> turbulence within the extraction tube, and the reduced system pressure <br /> (applied vacuum) results in the volatilization of VOCs from ground water <br /> to the vapor phase. The turbulence caused as the entrained ground water <br /> moves up the extraction tube can typically transfer up to 90 percent or <br /> more of VOCs from the liquid phase to the vapor phase (Test Plan and <br /> Teclmical Protocol for Bioslurping, Air Force Center for Enz7ironmental <br /> Excellence Technology Transfer Division, January 30, 1995). VOCs are <br /> typically more effectively treated in the vapor phase than in the liquid <br /> phase. <br /> 3-3 <br />