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B. Temporary Soil Gas Probe Emplacement Method: In general,the <br /> drive rod is driven to a predetermined depth and then pulled back <br /> to expose the inlets of the soil gas probe. After sample collection, <br /> both the drive rod and tubing are removed. <br /> 1. During installation of the probe, hydrated bentonite should be <br /> used to seal around the drive rod at ground surface to prevent <br /> ambient air intrusion from occurring. <br /> 2. The inner soil gas pathway from probe tip to the surface should <br /> be continuously sealed (e.g., a sampling tube attached to a <br /> screw adapter fitted with an o-ring and connected to the probe <br /> tip)to prevent infiltration. <br /> 2.2.6 Equilibration Time: During probe emplacement, subsurface conditions <br /> are disturbed. To allow for subsurface conditions to equilibrate, the <br /> following equilibration times are recommended: <br /> A For probes installed with the direct push method where the drive <br /> rod remains in the ground, purge volume test, leak test, and soil <br /> gas sampling should not be conducted for at least 20 minutes <br /> following probe installation. <br /> B. For probes installed with the direct push method where the drive <br /> rod does not remain in the ground, purge volume test, leak test, <br /> and soil gas sampling should not be conducted for at least 30 <br /> minutes following probe installation. <br /> C. For probes installed with hollow stem drilling methods, purge <br /> volume test, leak test, and soil gas sampling should not be <br /> conducted for at least 48 hours (depending on site lithologic or <br /> drilling conditions) after the soil gas probe installation. <br /> D. Probe installation time should be recorded in the field log book. <br /> 2.2.7 Decontamination: After each use, drive rods and other reusable <br /> components should be properly decontaminated to prevent cross <br /> contamination. These methods include: <br /> A 3-stage wash and rinse(e.g., wash equipment with a non- <br /> phosphate detergent, rinse with tap water, and finally rinse with <br /> distilled water); and/or <br /> B. Steam cleaning process. <br /> 2.3 Purge Volume Test <br /> To ensure stagnant or ambient air is removed from the sampling system and <br /> to assure samples collected are representative of subsurface conditions, a <br /> 01/28/2003 -8- <br />