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CRA <br /> 2/16 filter sand(Figure A). One-quarter inch diameter Nylon tubing of known length is attached to the probe. <br /> A 2-inch to 12-inch layer of dry bentonite chips is placed on top of the filter pack. Next,pre-hydrated granular <br /> bentonite is poured into the hole and topped with another 2-inch layer of dry bentonite chips or concrete, <br /> depending if the boring will hold one probe or multiple probes. The tube is coiled and placed within a well <br /> box finished flush to the surface. Soil vapor samples will be collected no sooner than one week after <br /> installation of the soil vapor points to allow adequate time for representative soil vapors to accumulate. Soil <br /> vapor sample collection will not be scheduled until after a minimum of five consecutive precipitation-free days <br /> and irrigation onsite has ceased. Figure B shows the soil vapor sampling apparatus. A measured volume of air <br /> will be purged from the tubing using a vacuum pump and a Tedlar bag. Immediately after purging,soil vapor <br /> samples will be collected using the appropriate size SUMMA canister with attached flow regulator and <br /> sediment filter. The soil vapor points will be preserved until they are no longer needed for risk evaluation <br /> purposes. At that time,they will be destroyed by extracting the tubing,hand-augering to remove the sand and <br /> bentonite,and backfilling the boring with neat cement. The boring will be patched with asphalt or concrete,as <br /> appropriate. <br /> Vapor Sample Storage, Handling, and Transport <br /> Samples are stored and transported under chain of custody to a state-certified analytic laboratory. Samples <br /> should never be cooled due to the possibility of condensation within the canister. <br /> Page 2 of 2 <br /> I <br /> I <br /> i <br />