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WEISS ASSOCIATES .4 <br /> sodium and sulfate are non-toxic, no STLCs have been established for these compounds. <br /> The samples will be reanalyzed for total Cr and Cu using nitric acid digestion (NAD) if <br /> the analytic results are above the Soluble Threshold Limit Concentration (STLC) for these <br /> compounds. If the analytic result is above the STLC for chromium the samples will be <br /> reanalyzed, using NAD, for total Hexavalent chromium by EPA Method 7196, colorimetric <br /> determination. <br /> The samples from beneath Tank 8 will also be analyzed by AA for total calcium and <br /> chloride. <br /> Several additional samples collected from uncontaminated native soil adjacent to the <br /> vaults will also be analyzed using these methods to indicate natural background <br /> concentrations of the compounds. The results of vault sample analyses will be compared <br /> to these background concentrations as an indication of possible leakage from the vaults. <br /> Strict quality assurance/quality control (QA/QC) will be maintained by the analytic <br /> laboratory. These measures will include the following: <br /> o One set of internal calibration standards for each analytic method is analyzed <br /> every eight hours. <br /> o Every tenth sample is analyzed in duplicate for each analytic method. <br /> o One internal laboratory method blank is analyzed for every 10 samples analyzed <br /> by each analytic method. <br /> o Every tenth sample is subjected to a spike analysis. <br /> WP1F:\ALL\331DWG\331R1AP8.DOC:74-331-00:V1.035 Page 17 <br />