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SECTIONTWO Summary of Field Sampling and Laboratory Analyses <br /> analytes The spike samples are then analyzed separately and the results are compared to j <br /> evaluate the effects of the sample matrix on the analytical accuracy and precision Accuracy is <br /> assessed by calculating the relative percent recovery (RPR) and precision is assessed by <br /> calculating the relative percent difference (RPD) US EPA considers an RPR between 25% to <br /> 130%, and an RPD value less than 20% to be acceptable (USEPA, 1994) <br /> 2.4 5 Laboratory Control Samples <br /> Laboratory control sample (LCS) recoveries and duplicate (LCSD) relative percent differences <br /> (RPDs) were reviewed as a check for analytical accuracy and precision The LCS is a known <br /> sample made by the laboratory for a specific analyte that is analyzed by the laboratory, and the <br /> percent recovery is compared to the original added amount of the analyte The LCS is created by <br /> the laboratory by taking a control sample of soil/water and adding a specific analyte, analyzing <br /> it, and then comparing the percent recovery to the original analysis of the soil/water sample <br /> 2.4.6 Surrogates <br /> Surrogate spike recoveries were reviewed to determine the efficiency of the sample preparation <br /> and the analytical process Surrogate spike samples are samples containing organic constituents <br /> not expected to be detected in environmental media and are added to every sample and QC at a <br /> known concentration <br /> Surrogate recoveries were all within the laboratory's QC limits <br /> 2.4.7 Summary <br /> The data reviewed are of acceptable precision and accuracy for use in this soil and groundwater <br /> assessment report <br /> URS Greiner Woodward Clyde I Z99670491UST REPORT CHEROKEE 00022 SEP 991\OAK 2-4 <br />