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Woodward-Clyde Consultants <br /> II QUALITY CONTROL <br /> ------------------ <br /> A. PROJECT SPECIFIC QC. Spikes and duplicates were analyzed <br />' at approximately 10% of the sample load in order to establish <br /> laboratory accuracy and precision. <br /> Precision is measured by using duplicate tests by Relative <br /> Percent Difference (RPD) as in: <br /> (sample concentration) (dupli.cate sample concentration) <br /> RPD - -------------------------------------------------------- * 100 <br /> { mean concentration of sample and duplicate sample ) <br /> Internal Accuracy (spike recovery) is measured by Percent <br /> Recovery (%REC) as in: <br /> ( spiked sample concentration } - ( sample concentration } <br />' %REC = ---------- ------------------------------ ---------------- * 100 <br /> ( true concentration of the spike <br /> ( See attached precision and accuracy summaries. ) <br /> B. METHOD PERFORMANCE. Precision and accuracy results were within <br /> EPA performance criteria for the method. <br />' C. METHOD BLANK RESULTS. A method blank is a laboratory-generated <br /> sample which assesses the degree to which laboratory operations <br /> and procedures cause false-positive analytical results for your <br /> samples. <br />' In the method blanks associated wth these samples, target <br /> parameters were not detected at or above the practical quantitation <br /> limits noted on the data sheets in the Analytical Results Section. <br />' ( See attached reagent water data sheet in Section III . ) <br />