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Stockton 99 Speedway Quality Assurance Project Plan April 12,2007 5.3.2 Laboratory QC Samples Laboratory QC samples will consist of method blanks, laboratory control samples, matrix spikes, matrix spike supplicate, and surrogate spikes. • Method blanks will be analyzed at a minimum frequently of one per batch and the concentration of target compounds in the blank must be less than the practical quantitation limit(PQ). • Laboratory control samples (LCSs) will be analyzed at a minimum frequency of one per batch. Laboratory control samples consist of blank spikes, which are used to determine the accuracy of analytical procedure by measuring a known concentration of an analyte of interest. • Surrogate spikes will be performed for all organic standards, samples and blanks. Each organic standard sample matrix spike, matrix spike duplicate, LCS and blank is spiked with surrogate compounds prior to purging or extraction. Surrogate spike recoveries must fall within the limits established by the analytical method and if a surrogate spike recovery is outside of acceptable ranges, then a corrective action will be taken. • Matrix spike/matrix spike duplicates (MS/MSD) are conducted to evaluate the matrix effect of the sample on the analytical method. The MS/MSD analyses will be performed at a minimum frequently of one per each group of 20 samples of the sample matrix. As a result, it is necessary to collect triplicate sample volumes in the field for one sample out of every 20. The RPD goal will �... be 20 percent. 5.4 Accuracy, Precision, Completeness, Representativeness, and Comparability The procedures used to. assess data are precision, accuracy, and completeness. In the absence of laboratory-specific precision and accuracy limits, the QC limits presented in this section must be met. 5.4.9 Precision Precision refers to the reproducibility of data under a specified set of conditions. Precision will be evaluated in conjunction with accuracy for the LCS samples. Precision will be determined using the MS/MSD samples and will be expressed as RPD. RPD is defined as: RPD = JX' —X 2 I X100 (X, +X2)12 Here, X1 and X2 refer to the larger and smaller of the two observed values, respectively. Acceptable levels of precision vary with the sample matrix, analytical method, and sample concentration. EPA precision data will be used as a basis for developing acceptance criteria for assessing precision. Qty�5 ,�Project P1en.Final.doc 5-4 The Source Group,Inc.