Laserfiche WebLink
pressure;or,well identification number and depth interval of <br /> screen. <br /> Typical sampling ports consist of a 1/4—inch ball valve fitted <br /> with a 3/16-inch hose barb to form a slip stream from the <br /> sample source. <br /> The sampling procedure requires one end of the tubing be <br /> slipped over the sample port hose barb and the other end <br /> over the diaphragm pump inlet hose barb to form an air-tight <br /> connection. The sampling pump is then started and the <br /> pump is purged for 1 minute with the vapor to be sampled. <br /> Following purging,the discharge of the pump is then <br /> connected to the"Tedlar"bag using a section of 3/16-inch <br /> tubing.The pump is restarted and the bag is opened and <br /> allowed to fill to approximately 3/4 of its capacity. Caution <br /> should be taken not to overfill the sampling bag. The sample <br /> is placed in a non-refrigerated dry cooler with sufficient <br /> packing to prevent damage during transport. Cooling <br /> samples will cause condensation of moisture within the <br /> sample,thereby distorting the laboratory analysis. <br /> For quality control purposes,a duplicate vapor sample <br /> should be collected from each sampling port. This sample is <br /> then put on hold at the laboratory pending initial analysis. To <br /> ensure quality control and minimize the potential for cross- <br /> contamination prior to and during sampling,the diaphragm <br /> pump is thoroughly purged for approximately 5 minutes with <br /> nitrogen or clean air(i.e.,compressed clean air). A"blank" <br /> sample of the discharged air is captured in a'Tedlar"bag at <br /> the end of the purging procedure and may be analyzed to <br /> ensure the purging was effective. <br /> To minimize the potential for cross-contamination between <br /> air samples,the polyethylene tubing,if not sample dedicated, <br /> is thoroughly cleaned and rinsed. <br /> Vapor samples are subject to very limited holding times, <br /> typically 48 hours. Thus,care must taken to avoid delays in <br /> submittal of vapor samples to the laboratory. In the event the <br /> vapor samples cannot be submitted to the analytical <br /> laboratory on the same day they are collected,they are to be <br /> temporarily stored in the dry,non-refrigerated,packed cooler <br /> until the very first opportunity for submittal well within the <br /> required holding time,taking into account the time needed for <br /> shipment to and receipt by the laboratory. <br />