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with a special septum "valve" and tubing bib, to the sample port . The sample port is on the vaccum side of the pump and therefore a vacuum greater than the well vacuum must be exerted on the outside of the tedlar bag to " fill" the bag with the vapor sample A special vacuum box, in which the tedlar bag is sealed inside, is used to exert a high vacuum to the exterior of the bag, thereby pulling a sample into the bag Once the tedlar bag is filled, its valve is closed and locked and the appropriate label is placed on the bag The label shows the date, time, sample ID# and analyses to be run and the sampler' s initials The tedlar bag samples are then placed within a cooler, and are hand delivered to WEGE' s laboratory that same day The vapor sample is then in3ected into an FID (Flame Ionizing Detector) chromatograph and the resulting chromatogram compared to standard chromatograms of known TFH (Total Fuel Hydrocarbons, gasoline) and BTEX (benzene, toluene, ethylbenzene, and xylenes) concentrations A dual chromatograph comparison is also run (Photovac 10550) to evaluate BTEX, TCE, PCE, and DCE Carbon dioxide (CO2) concentration is measured in the tedlar bag samples by connecting a Drager tube to the inlet of the tedlar bag that measures only CO2 reaction in percent any using a Drager pump to move the sample through the tube A direct reading in percent is then obtained and recorded on the chrmoatogram produced from the GC-FID analysis ON SITE ANALYSIS During the two hour tests, a photoionizing detector (HNu PTD w/10 2 ev bulb) and/or GasTech LEL/02 meter are used to perform constant exhaust monitoring, see Field Notes - Appendix A The LEL was used to insure that less than two pounds of hydrocarbons would be emitted during the test A common used LEL for gasoline is 1 . 40-. = 14, 000 ppmv * mg/L/250 ppmv * 6 21X10-5 * flow rate (cfm) * 120 minutes = 1 04 lb at 5% LEL and 2 08 lbs at 10% LEL The extraction well vacuum and flow is measured with a mercury manometer and the surrounding wells were gauged with a water manometer FLOW RATES Flow rates are measured at the site by use of a orifice plate A one inch orifice-sampling manifold is placed directly on the casing of the monitor well , carefully avoiding any vacuum leaks An orifice plate restricts the flow of air across it . This restriction causes a pressure drop across the orifice By measuring the resulting pressure change across the orifice it is possible to calculate the air flow rate The flow rate is calculated by the pressure drop (millimeters (mm) mercury or water) across a square edge orifice plate. PAGE 3