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I 06 October 2008 AGE-NC Project No, 06- 1457 Page 5 of 7 As the vacuum is applied to the extraction tube, a high velocity vapor stream is generated in the stinger. A vacuum is created and maintained by adapting the well head with a 4-inch diameter, tightened rubber well sanitary seal or rubber seal containing a 1 -inch diameter opening for the suction tubing and attached stinger to be placed through. The well head connection details are shown M n Figure 5 . The vapor stream entrains the impacted ground water and lifts the hydrocarbon vapor/water to a treatment system. As the hydrocarbon-laden water travels up the extraction stinger, the majority of the contaminants in the ground water are stripped into vapor phase by the high velocity vapor stream. Stripping efficiencies of greater than 90% are possible (MTBE); however, stripping efficiency is dependent upon site-specific variables, including vacuum, air/water ratios, contaminant concentrations and contaminant physical properties . Extractedwater and vapor are held within a 300 gallon "knock out' vessel integrated onto the DPE system. 4.2 DPE SYSTEM OPERATION AND PILOT STUDY MONITORING The most significant soil contamination is located between 40 and 50 feet bsg. The current depth to ground water is approximately 25 feet across the site. Extraction well EW- 1 is screened from 3 5-5 5 feet bsg through this area of contamination and will expose the most heavily impacted soil. Assuming the extraction system is successful in drawing well EW-1 down to a depth of 55 feet bsg, there will be an exposed screen interval of approximately 20 feet. Monitoring wells are screened from 35 to 55 feet bsg (MW- 1 and MW-3), 25 to 45 feet bsg (MW-2), and 30 to 50 feet bsg (MW- 4); vapor wells are screened from 15-35 bsg. These wells will be utilized to determine the radius of influence and ground water draw down. 4.2. 1 . Field Measurements i During the DPE pilot test the air flow will be monitored using a Dwyer DS-200 flow sensor. Flow rate will be determined from the measured differential pressure and the piping diameter using a nomograph. Flow rates will be measured and documented in standard cubic feet per minute (scfm), inches of water of differential pressure. Induced vacuum measurements will be recorded from the surrounding observation wells daily utilizing Magnehelic gauges. The induced vacuum will be monitored for stabilization in units of inches of water and/or inches of Hg during the pilot test. Hydrocarbon concentrations in the well influent and effluent stream will be measured at regular intervals using an OVM. Depth to water measurements will be taken from the surrounding observation wells dailyto determine ground water draw down. Advanced GeaEnvironmental, Inc.