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t Tracer Research Carporatlon Continuing calibration checks are analyzed to verify the detector response for the target VOCs If the response changes by more than 25 percent, the gas chromatograph is recalibrated and new response factors are calculated Field system blanks are analyzed to check for contamination of the sampling apparatus, e g ,`probe and sampling synnge A sample is collected using standard soil gas sampling procedures, but without putting the probe into the ground The results are compared to those obtained from a concurrently sampled ambient air analysis If the blanks detect compounds of interest at concentrations that indicate equipment contamination or concentrations that exceed normal background levels ~� (ambient air analysis), corrective actions are performed If the problem cannot be corrected, an out-of-control event is documented and reported I A reagent blank is performed to ensure the solvent used to dilute the stock standards is not contaminated Analytical instruments are calibrated daily using fresh working standards made from National Institute of Sciences and Technology a (NIST) traceable standards and reagent blanked solvents Quantitative precision is assured by replicating analysis of 10 percent of the samples Replicate analyses are performed by subsampling vapors from the original syringe and VOA 7 0 RESULTS The analytical results from this soil gas and groundwater investigation are i condensed in Appendix A The data are presented by location and by analyte concentration. When the compound was not detected, the detection limit is presented as a "less than" value, e g , <0 1 Rg/L Samples are identified by sample type, sample location, and sampling depth For example, SG-1-12' represents a soil gas sample collected from soil gas location 1 c 1 at a depth of 12 feet bgs Sample WS-4-11' represents a water sample collected from groundwater location 4 at a depth of 11 feet bgs July 19,1994 Page 9 11402915 4