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€ MUM <br /> �£ <br /> p _ _ <br /> x Tracer Research Corporatlan <br /> Injector port septa through which soil gas samples are injected into the <br /> chromatograph are replaced on a daily basis to prevent possible gas Ieaks from the <br /> chromatographic column. <br /> Analytical instruments are calibrated each day by analytical standards from <br /> Chem Service, Inc. Calibration checks are also run aAer approximately _very five <br /> soil gas sampling locations. <br /> Subsampling syringes are checked for contamination prior to sampling each <br /> day by injccting nitrogen carrier gas into the gas chromatograph. <br /> Prior to sampling each day, system blanks are run to check the sampling <br /> apparatus (probe, adaptor, 10 cc syringe) for contamination by drawing ambient air <br /> from above ground through the system and comparing the analysis to concurrently <br /> sampled ambi:nt air analysis. <br /> All sampling and subsampling syringes are decontaminated each day and no <br /> such equ=ipment is reused before being decontaminated. Microliter size subsampling <br /> + syringes are reused only after a nitrogen carrier gas blank is run to insure it is not <br /> contaminated by the previous sample. <br /> Soil gas pumping is monitored by a vacuum gauge to insure that an adequate <br /> gas flow from the vadose zone is maintained. A reliable gas sample can be obtained <br /> if the sample vacuum gauge reading is at least 2 inches Hg less than the maximum <br /> pump vacuum. <br /> 6 <br />