SITE INFORMATION AND CORRESPONDENCE

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Attachment B: Data Usability Summary and Laboratory Chemical Analytical Report Method Blank Results All laboratory method blanks were free of contamination. Field QC Results One equipment blank and one trip blank were submitted with the field samples. The equipment rinsate and trip blank were free of contamination,with the exception of a trace concentration of TPHd in equipment rinsate blank sample QA-R-060504. TPHd were detected at 89 micrograms per liter(gg/L). The concentration is between the laboratory MDL and reporting limit, and the result was flagged J to indicate the concentration is an estimate. The lab noted that the observed chromatogram pattern is not typical of#2 fuel/diesel, and the reported result is due to groupings of peaks eluting in the TPHd range. After the silica gel-cleanup process, QA-R-060504 had a non-detect result. TPHd were only detected at a similar concentration in one associated field sample,MW-5-W-060504. The laboratory noted the chromatogram pattern for this sample also did not resemble diesel, and had a non-detect result after the silica-gel cleanup. This indicates that the results reported for the TPHd for QA-R-060504 and in MW-5-W-060504 were not due to target analytes. Therefore,the trace detection in the equipment rinsate does not indicate nonconformances with equipment decontamination procedures. 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. 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,when required by the analysis,were less than the acceptance pH limit of 2. MDLs and Reporting Limits The laboratory reported results between the MDL and reporting limit. The MDL represents the lowest concentration point where an analyte can be positively identified,but the quantitation is an estimate. The reporting limit is the lowest concentration of an analyte in a sample that a laboratory can report with precision and accuracy. Analytes that were reported between the MDL and reporting limit were flagged J as estimates. Laboratory Fuel Notes for TPHd Analysis The laboratory noted that the observed hydrocarbon fuel pattern for TPHd analysis in sample MW-7-W-060504 and its field duplicate MW-7-WD-060504 included#2 fuel/diesel and an additional pattern that elutes later in the target carbon range. TPHd were reported at 710 µg/L in sample MW-7-W-060504, and 550 µg/L in field duplicate sample MW-7-WD-060504. After silica-gel cleanup, TPHd were 52 µg/L in MW-7-W-060504 and were not detected in MW-7- WD-060504. This indicates the TPHd results were likely biased high due to biogenic material that was removed during silica-gel analysis. The laboratory noted the observed chromatogram pattern for TPHd analysis in sample MW-5-W- 060504 and equipment rinsate QA-R-060504 did not resemble#2 fuel/diesel and the reported results for the samples are due to groupings of peaks eluting in the target carbon range. After silica-gel cleanup,there were non-detect results for TPHd,which indicates the TPHd results were likely due to non-target interferences in the sample matrix.