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' Tracer Research Corporation <br /> Field blanks are analyzed to check for contamination of the sampling <br /> ' apparatus, e.g., probe, sampling manifold, sampling pump, and vacuum line. A <br /> sample is collected using standard soil gas sampling procedures, but without putting <br /> the probe into the ground. The results are compared to those obtained from a <br /> concurrently sampled ambient air analysis. <br /> If the blanks detect compounds of interest at concentrations that indicate <br /> equipment contamination or concentrations that exceed normal background levels <br /> ' (ambient air analysis), corrective actions are performed. If the problem cannot be <br /> corrected, an out-of-contrat event is documented and reported. <br /> A reagent blank is performed to ensure the solvent used to dilute the stock <br /> ' standards is not contaminated. Analytical instruments are calibrated daily using <br /> fresh working standards made from National Institute of Sciences and Technology <br /> ' traceable standards and reagent blanked solvents. <br /> Quantitative precision is assured by duplicating analysis of at least 20 percent <br /> of the soil gas samples. Duplicate analyses are performed by subsampling vapors <br /> from the original syringe. If short analysis times are involved, 100 percent of the <br /> ' samples are analyzed in duplicate. <br /> ' 7.0 RESUL'T'S <br /> The analytical results from this soil gas investigation are condensed in <br /> Appendix A. A field map is included in Appendix B. The data are presented by <br /> location and by analyte concentration. When the compound was not detected, the <br /> detection limit is presented as a "less than" value, e.g., <0.0001 ug/l. <br /> ' Samples are identified by sample type, sample location, and sampling depth. <br /> For example, SG-1-12' represents a soil gas sample collected from location 1 at a <br /> ' depth of 12 feet below grade. Sample WS-412' represents a water sample collected <br /> from location 4 at a depth of 12 feet below grade. <br /> TVHC were detected in five samples. In the three soil,gas samples, <br /> concentrations of TVHC ranged from 0.6 to 3 ug/l. In the two groundwater samples, <br /> concentrations ranged from 9 to 25 ug/l. The tables on the following page <br /> summarize the results of the investigation: <br /> May 22. 1992 Page 9 1-92-358 <br />