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Tracer L earch Corporation <br /> I � . <br /> -Sampling Efficiency <br /> Soil gas pumping is monitored by a vacuum gauge to ensure that an adequate flow <br /> of gas from the vadose zone is-maintained. A reliable gas sample can be obtained if the <br /> sample vacuum gauge reading is at least 2 inches Hg less than the maximum measured <br /> vacuum of the vacuumum . <br /> P P <br /> Analytical Quality Assurance Samples <br /> Quality assurance samples are performed at the below listed, or greater, frequencies <br /> �. according to the number of soil gas samples analyzed: <br /> Table 2.' Quality Assurance Samples <br /> ( Sample type Frequency <br /> Ambient Air Samples' 2 per day or per site <br /> Analytical Method Blanks 5% (1 per.20 samples or 1 a day) <br /> Continuing Calibration Check., 20% (1 every 5 samples) <br /> Field System Blank 10% G every.10 samples or 1 a day) <br /> Reagent Blank l.per set of working standards <br /> Duplicate Samplesr 20% to 100% of all soil gas samples <br /> The ambient air samples are obtained on site by sampling the air immediately <br /> outside the mobile analytical van and directly injecting it'into the GC. Analytical method <br /> blanks are taken to demonstrate that theanalytical instrumentation is not contaminated. <br /> These are performed by injecting carrier gas (nitrogen) into the GC with the sampling <br /> L <br /> syringe. Subsampling syringes are also checked in this fashion. <br /> t <br /> May 21,1992 Page 6 1-92-302 <br />