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am� <br /> 1V <br /> 2. Direct-push soil vapor sampling probes(post-run tubing system,PRT) <br /> The PRT system involves the use of a drive point holder (located just above the drive <br /> point) that also serves as the soil vapor sampling probe (Figure 3). Both expendable and <br /> retrievable drive point/drive point holder systems are available. Note that the PRT <br /> system allows for soil vapor samples to be obtained from multiple depths from a single <br /> borehole during a single sampling event. Thus the PRT system is not acceptable for <br /> human health risk assessment activities unless the probe permanently remains at the first <br /> interval sample. <br /> First, the drill rods and drive point/drive point holder are pushed to the shallowest <br /> designated depth. Then, an adapter connected to nylon sampling tubing that extends to <br /> the ground surface is attached to the drive point holder. Leakage of atmospheric air <br /> through the drive rods into the drive point holder(the vapor sampling probe) is prevented <br /> by o-rings that are part of the adaptor assembly. After a soil vapor sample is obtained <br /> (described in Section III), the adaptor/tubing assembly is removed, and the tubing is <br /> discarded. The drive point/drive point holder is then pushed deeper into the subsurface <br /> until the next designated sampling depth is reached. The adaptor/tubing assembly, with a <br /> new piece of nylon tubing attached, is then connected to the drive point holder and the <br /> soil vapor sampling process is repeated. This process can be repeated over multiple <br /> depths. With the expendable PRT system, the drive point/drive point holder assembly <br /> remains in the subsurface when the rods are withdrawn, while for the retrievable PRT <br /> system the entire apparatus is removed. <br /> ETC Soil Vapor Sampling Technical Toolkit 10 <br /> Version 1.4,September 7,2005 <br />