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sampling system connections such that the bags are open to the connections but closed to <br /> the atmosphere. Soil vapor sampling (described below) is performed immediately after <br /> the bags are wrapped in place. If the sampling system connections are tight, isopropanol <br /> will not be detected in the soil vapor sample. It is critical that clean sampling techniques <br /> are used so that isopropanol does not inadvertently contaminate sampling equipment. Do <br /> not store isopropanol with the sampling equipment, and wear and periodically change <br /> gloves when using isopropanol. Do not spill isopropanol on sampling equipment. If the <br /> soil vapor analytical results show isopropanol above a concentration of 10 pg/L (in <br /> California) or 100 pg/L, the sampling system must be inspected/re-evaluated and the <br /> location of the leak found (check applicable regulations to determine leak test pass/fail <br /> concentrations). If the leak test fails, resampling of the probe should be performed. If <br /> isopropanol is detected in the next sampling event (after any necessary equipment <br /> changes have been made), then the soil vapor probe may be incorrectly installed and may <br /> need to be decommissioned. The presence of any leakage should be recorded, as should <br /> all techniques used in the leak testing process. Maintain consistency of the leak testing <br /> process over multiple sampling events. <br /> F. Sample collection <br /> There are numerous combinations of tubing, connectors,pumps, and sampling containers <br /> that have been used for soil vapor sample collection. Note that the design of the <br /> sampling equipment should be such that the internal volume is minimized in order to <br /> keep the necessary purge volume small. In all cases, a vacuum is used to draw soil vapor <br /> from the subsurface to the sample container. The recommended method involves using a <br /> Summa canister under vacuum conditions to withdraw the soil vapor sample from the <br /> subsurface. A portable pump can also be used but is not recommended. Note that <br /> equipment must be decontaminated prior to sampling and that leak testing should be <br /> performed during the sampling process. An example of the equipment arrangement used <br /> for soil vapor purging and sampling is shown in Figure 11. <br /> ETC Soil Vapor Sampling Technical Toolkit 19 <br /> Version 1.4, September 7, 2005 <br />