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Attachment B: Data Usability Summary and Laboratory Chemical Analytical Report Data QC Objectives SAIC evaluated the project analytical data according to the following parameters in order to determine their usability: • Precision • Accuracy • Representativeness • Completeness • Comparability Data Usability Summary The following sections summarize the findings of the data evaluation process. A summary of qualified data is provided in Table B-1. Precision and Accuracy The precision and accuracy of field and laboratory QC samples were evaluated. The calculated relative percent difference (RPD)of laboratory control samples and laboratory control sample duplicates(LCS/LCSDs)provided information on the precision of laboratory analyses. Evaluation of the percent recoveries(%Rs) of LCS/LCSDs and surrogates provided information on accuracy. All LCS/LCSD %Rs were within the laboratory control limits. All surrogate%Rs were within the laboratory control limits,with the exception of one sample. The surrogates used in the analysis for PAHs by EPA Method SW8270C-SIM in field duplicate sample MW-7-WD- 060504 were below the required laboratory control limits. The laboratory repeated the analysis and the surrogates were within the control limits,but the required hold time for the sample extraction had passed. The initial results were reported, and qualified"J"for analytes that were detected, and"UJ"for analytes that were not detected to note the nonconformance. A potential low bias is associated with the field duplicate sample results because the surrogate recoveries were low. The data were not rejected as they are used for qualitative purposes, and the field sample,MW-7-W-060504, is the sample that will be used for risk assessment. The surrogates associated with MW-7-W-060504 for PAHs were all within the required control limits. Project- specific matrix spike and matrix spike duplicate samples were not submitted with the samples. Field Duplicates Sample MW-7-WD-060504 is a field duplicate of sample MW-7-W-060504. Field duplicate RPDs were assessed for analytes detected in both the field sample and field duplicate above the reporting limit. TPHd and acenaphthene were the only analytes detected above the reporting limit in both the field and field duplicate sample. The RPD for TPHd was 25 percent,which is below the control limit of 30 percent. The RPD for acenaphthene was 115 percent,which exceeds the control limit of 30 percent. The analyte was flagged J in the field sample and the field duplicate sample to indicate the nonconformance. Phenanthrene was detected in the field and field duplicate sample,but the concentrations were below the reporting limit and a RPD was not calculated. Concentrations detected between the method detection limit(MDL)and reporting limit are estimated and are not used to assess precision. Representativeness Representativeness was assessed through the evaluation of method blank samples, trip blank samples, equipment blank samples, chain-of-custody forms,preservation, and holding times.