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Appendix C:Data Usability Summary and Analytical Reports • TPH quantified as diesel(TPHd; CIO—C25)by EPA Method 8015 Modified and with a silica-gel cleanup(TPHdsg)to remove biogenic compounds; and • PAHs by EPA Method 8270 C SIM. Data QC Objectives The SAIC evaluated project analytical data according to the following parameters in order to determine their usability: • Precision; • Accuracy; • Representativeness; • Completeness; and • Comparability. Data Usability Summary Based on the results of the data evaluation,the analytical data of concern are summarized in Table C-1. The data evaluation and usability summary are described below. Precision and Accuracy The precision and accuracy of field and laboratory QC samples were evaluated. The calculated relative percent difference (RPD)of laboratory control sample samples and laboratory control sample duplicates (LCS/LCSDs) and matrix spike and matrix spike duplicates(MS/MSDs)provided information on the precision of laboratory analyses and field sampling procedures. Evaluation of the percent recoveries of LCS/LCSDs,MS/MSDs, and surrogates provided information on accuracy. The control limits for these parameters are provided in the document entitled Quality Assurance& Control: Sample Collection, Handling, and Analysis; Chevron Texaco Historic Pipeline Portfolio Sites, California, dated November 2004. 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. Method Blank Results All laboratory method blanks were free of contamination. Field QC Results Field QC included equipment rinsate blanks and trip blanks. All equipment rinsate and trip blanks were free of contamination. Chain-Of-Custody Forms Sample analytical results were evaluated for agreement with the chain-of-custody form. Based on the evaluation, all samples were received at the lab in the appropriate containers and in good condition with the chain-of-custody form filled out properly. Note, sample SB-24-S-61-050524 was mislabeled by the laboratory. According to the chain-of-custody form,the field sample ID should be SB-24-S-61-050520. Preservation and Holding Times Samples were preserved in the field as appropriate,were received at the laboratory within the acceptance temperature criterion of 4+2 °C, and were prepared and analyzed within specified holding times. The sample preservations were less than the acceptance pH limit of 2 with the exceptions noted in Table C-1. Because the concentration of any COC in an inadequately-preserved sample would tend to be degraded, C-2 From Science to Solutions-