ARCHIVED REPORTS_FIRST QUARTER 2007 GROUNDWATER MONITORING AND SAMPLING REPORT

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' Data Usability Summary Page 3 of 4 Representativeness Representativeness was assessed through the evaluation of method blank samples,trip and equipment blank samples,chain-of-custody forms,preservation,and holding times. ' Method Blank Results TPHd were detected at 34 micrograms per liter(pg/L),below the laboratory LOQ of 100 pg/L, in the method blank associated with sample MW-5-W-070124. TPHd were detected at 150 pg/L in sample MW-5-W-070124. Concentrations that are within five times the amount detected in an associated method blank are likely biased by contamination introduced due the handling or analysis of the sample. In this case,the result in the field sample was within five times the amount detected in the method; however, because TPHd were detected above the laboratory LOQ, the historical data was evaluated to determine whether the result is representative of field conditions. TPHd were detected below the laboratory LOQ at 72 pg/L in the last sample collected at MW-5 in May 2006. This indicates the current result of 150 pg/L ' may be biased high from contamination introduced during the analysis. The result for TPHd in sample MW-5-W-070124 was qualified E to indicate the result may be biased. ' Field QC Results One equipment rinsate blank,QA-R-070124,was submitted with the samples. Naphthalene was detected at 0.056 pg/L, which is above the laboratory LOQ of 0.05 pg/L. Naphthalene was detected in the ' associated field sample,MW-5-W-070124, at 0.064 pg/L. Target anlayte detected in equipment rinsate blanks may indicate that the sample was contaminated during sample collection,handling, and/or analysis. The naphthalene result in MW-5-W-070124 was qualified E because this review could not ' determine if the result was representative of field conditions. Data collected at this location during future monitoring events will be used to determine representativeness. 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. The samples were prepared and analyzed within specified holding times. Reporting Limits Data reported for this sampling event were reported with the laboratory MDLs. The MDL represents the lowest concentration point where an analyte can be positively identified,but the quantitation is an estimate. The LOQ is the lowest concentration of an analyte in a sample that the laboratory can report ' with precision and accuracy. Analytes that were reported between the MDL and LOQ for this data set were qualified J as estimates. ' Laboratory Fuel Notes for TPHd Analysis The laboratory noted that the observed hydrocarbon fuel pattern for TPHd analysis in sample MW-5-W- 070124 is not typical of#2 fuet/diesel. The reported result is due to groupings of peaks eluting in the ' DRO range. The sample was also silica-gel cleaned prior to the analysis and TPHd were not detected after the silica-gel cleanup. This indicates the TPHd results could be biased high due to biogenic material that was removed during silica-gel analysis. Data were not qualified for the TPHd fuel pattern note. t -=yO s CC aJr7/%o�' From Science to Solutions