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Quality Assurance Project Plan for Removal Action <br /> APN 209-450-03,Mountain House,CA <br /> Page 5 <br /> Analytical precision is a measurement of the variability associated with duplicate or replicate analyses of <br /> the same sample in the laboratory, and is determined by analysis of laboratory quality control samples <br /> (LCSD), such as duplicate control samples (DCS), matrix spike duplicates (MSD), or sample duplicates. <br /> If the recoveries of analytes in the specified control samples are comparable within established control <br /> limits,then precision is within acceptable limits. <br /> Total precision is a measurement of the variability associated with the entire sampling and analytical <br /> process. It is determined by analysis of duplicate or replicate field samples, and measures variability <br /> introduced by both the laboratory and field operations. Field duplicate samples are analyzed to assess both <br /> field and analytical precision. <br /> Duplicate results are assessed using the relative percent difference (RPD) between duplicate <br /> measurements. If the RPD for laboratory quality control samples exceeds 30 percent, data will be <br /> qualified as described in the applicable validation procedure. If the RPD between primary and duplicate <br /> field samples exceeds 100 percent for soil, data will be qualified as described in the applicable validation <br /> procedure. The RPD will be calculated as follows: <br /> 200 x X2—XI <br /> RPD (%) _ <br /> X2+XI <br /> where XI is the larger of the two observed values, and X2 is the smaller of the two observed values. <br /> 4.2.2 Accuracy <br /> Accuracy is a statistical measurement of correctness and includes components of random error(variability <br /> due to imprecision) and systematic error. It reflects the total error associated with a measurement. A <br /> measurement is accurate when the value reported does not differ from the true value or known <br /> concentration of the spike or standard. <br /> Accuracy of laboratory analyses will be assessed by laboratory control samples, surrogate standards, <br /> matrix spikes, and initial and continuing calibrations of instruments. Laboratory accuracy is expressed as <br /> the percent recovery (%R). Statistically derived laboratory accuracy limits are included with the <br /> respective laboratory QA plans. If the percent recovery is determined to be outside of acceptance criteria, <br /> data will be qualified as described in the applicable validation procedure. The calculation of percent <br /> recovery is provided below; where XS is the measured value of the spiked sample,X is the measured value <br /> of the unspiked sample, and T is the true value of the spike solution added. <br /> 100xXs—X <br /> %R = <br /> T <br /> Field accuracy will be assessed through the analysis of field equipment blanks. Analysis of blanks will <br /> monitor errors associated with the sampling process, field contamination, sample preservation, and <br /> sample handling. The DQO for field equipment and trip blanks is that all values for equipment blanks are <br /> less than the reporting limit for each target constituent. If contamination is reported in the field equipment <br /> or trip blanks, data will be qualified as described in the applicable validation procedure. <br /> t4k <br /> CONDOR <br />