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Tracer tl.Aearch Corporation <br /> l <br /> The injector port septa through which soil gas samples are injected into the GC are- <br /> replaced daily to prevent possible gas leaks from the chromatographic column. All <br /> sampling and subsampling syringes are decontaminated afier use and are not used again <br /> until-they have been decontaminated by washing in anionic detergent and,baking at.100'C. <br /> Field blanks are analyzed to check�for contamination of the sampling apparatus, <br /> e.g., probe, sampling manifold, sampling pump, and vacuum line.° A sample is collected <br /> using standard soil gas sampling procedures, but without putting the probe into the ground. <br /> The results are compared io those obtained from-a concurrently sampled ambient air <br /> analysis. <br /> If the blanks detect compounds of interest at concentrations that indicate equipment <br /> contamination.or concentrations that exceed normal background levels (ambient air <br /> analysis), corrective actions are performed. If the problem cannotbe corrected, an <br /> out-of-control event is documented and reported. <br /> A reagent,blank is performed to ensure the solvent used to dilute� p the stock <br /> standards is not contaminated. Analytical instruments are calibrated daily using'fresh <br /> working standards made from National Institute of Sciences and Technology traceable <br /> standards and reagent blanked solvents. <br /> 4 _ <br /> Quantitative.precision is assured by duplicating analysis-of at least 20 percent of <br /> the soil gas samples. Duplicate analyses are performed by subsampling vapors from the . <br /> original syringe. If short analysis times are involved, 100 percent of the samples are <br /> analyze&in duplicate. <br /> 6.0 RESULTS <br /> The analytical results from this soil gas:investigation are condensed in Appendix A. <br /> The data are resented b location and b anal <br /> p y y analyte concentration. When the compound-was <br /> not detected, the detection limit is presented.as a "less than" value, e.g., <0.0001,ug/l. The <br /> data is also provided in.parts per billion by'volume (ppbv). A copy of the field logbook is <br /> in Appendix B. <br /> jl Soil gas samples are identified by sample location and sampling depth. For <br /> example,.SG-1-4' represents soil gas sample number one, collected at a depth of 4 feet <br /> below the ground surface. A summary of the soil gas samples is presented in a table on the <br /> following page. <br /> May 2 f,1992 Page 7 1-92-302 <br />