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The following equations are used to calculate the purge volumes and associated vacuum <br />2 <br />= rr H Li x ve + <br />2 <br />Va = rr Daj2 h x cp1+ 0.7(171, ) <br />2 <br />D. <br />pressure drops: <br />V, = System Volume <br />D, = Tubing Inner Diameter (in inches) <br />L = Tubing Length (in inches) <br />x = Conversion Constant (16.39 mL/in3) <br />V. = Annulus Volume <br />Vm = Manifold Volume <br />Vi = Summa Canister Volume <br />P, = Initial Summa Pressure <br />= System Volume <br />Pp = Purge Pressure Drop <br />V. = Annulus Airspace Volume <br />D. = Annulus Diameter <br />h = Annulus Height <br />x = Conversion Constant (16.39 mL/in3) <br />cp = Porosity <br />Vp = Vapor Point Volume <br />In order to check for system leaks at the connection point not tested by the initial leak check <br />(the tubing connections at the downhole side of the ball valve), an atmosphere of laboratory <br />grade helium is introduced as a tracer gas surrounding these connections. A shroud lowered <br />over the well and foam is used to create a seam against the uneven surface. The shroud is <br />equipped with several bulkhead fittings that allow the shroud to be filled with at least 10% <br />laboratory grade helium to create an atmosphere of the tracer gas inside the shroud. A helium <br />detector is also inserted through the bulkhead fitting and is used to monitor the tracer <br />atmosphere to document that it remains relatively constant during sample vapor sample <br />collection. A sample of the shroud atmosphere is collected in a Tedlar bag for analysis to help <br />calibrate the detector readings. The soil vapor is collected by closing the valve on the purge <br />Summa canister and opening the valve on the sampling Summa canister. The sampling start <br />time is recorded on the field data sheet. After approximately one half hour, depending on the <br />soil materials, the sampling canister valve is closed and the end time is recorded. The pressure <br />on the sampling canister is checked to verify that sufficient pressure drop has occurred to <br />indicate that an adequate sample volume has been collected, and that a residual vacuum <br />pressure of approximately -5 inHg remains in the Summa canister at the completion of sampling. <br />Prior to sampling subsequent sample locations, the used tubing is discarded. <br />The sampling canister(s) and chain of custody is labeled with the site name, sampling ID, time <br />and date of sampling, final vacuum pressure, and the canister serial number. The sampling <br />canister(s) are shipped to a California certified laboratory for analysis. <br />Stantec