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ADVISORY - ACTIVE SOIL GAS INVESTIGATIONS <br />6.5 SOIL GAS SAMPLE ANALYSIS AND LABORATORY REPORTING <br />6.5.1 Analytical Methods <br />At sites that are not fully characterized, soil gas samples should be analyzed using only <br />USEPA modified analytical methods 8260B, TO-15, TO-17, or equivalent. At well- <br />characterized sites, alternative methods may be used for monitoring contamination <br />where VOCs are known to be present and confirmed based on previous gas <br />chromatograph/ mass spectrometer (GC/MS) analyses. Non-specific portable organic <br />vapor analyzers and/or GC-based hand-held detectors can provide useful information for <br />selecting samples for laboratory analysis and verifying the integrity of collected samples. <br />However, these instruments are not acceptable substitutes for compound-specific <br />analysis due to a lack of QA/QC protocols. The various available VOC analytical <br />methods are discussed in detail in Appendix F. Additional discussion is provided in <br />Appendix E specific to soil gas containing naphthalene. <br />If new VOC(s) are detected by a non-GC/MS method during routine monitoring, then at <br />least 10 percent of the samples for each newly identified VOC should be confirmed by a <br />GC/MS method. Thereafter, routine monitoring can resume with the non-GC/MS <br />method, including the newly identified analyte(s). <br />6.5.2 Contaminant Reporting <br />Laboratory reports should contain the analytical results for all identified quantifiable <br />contaminants, along with all tentatively identified compounds (TICs) with an estimated <br />concentration. The site's QAPP should specify that TICs will be identified and reported. <br />6.5.3 Leak Check Compounds <br />Liquid and gaseous leak check compounds should be included in the laboratory analyte <br />list. The laboratory reports should quantify and annotate all detections of the leak check <br />compound the target analyte reporting limits. For additional information on leak check <br />compounds, refer to Section 4.2. <br />6.5.4 Auto Samplers <br />Using an autosampler with modified USEPA Method 8260B/C for soil gas analysis is not <br />reliable. Sample loss may occur from the vials during the sample transfer and sample <br />run. In addition, the vials may sit in the autosampler for an extended period of time <br />which may compromise the sample through leakage at the vial seal (See Appendix F, <br />GC/MS Methods Section for additional information). <br />July 2015 39