ARCHIVED REPORTS_THIRD QUARTER 2011 SITE STATUS, REMEDIAL SUMMARY, AND GROUNDWATER MONITORING REPORT

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Stantec L & M OPERABLE UNIT- THIRD QUARTER 2011 SITE STATUS, REMEDIAL SUMMARY, AND GROUNDWATER MONITORING REPORT Groundwater Monitoring and Sampling October 28, 2011 2.4.2.6 Quality Assurance/Quality Control Samples Duplicate samples QCDUP-2 and QCDUP-4 were collected from L&M OU deep zone wells MW-44 and MW-27, respectively, during 3Q11 sampling event. A comparison of the samples is shown below. Analyte Sample # Sample # % Difference MW-44 QCDUP-2 TPHg (mg/L) <0.05 <0.05 0% TPHd (mg/L) 0.14 0.096 +/- 37.3% TPHo (mg/L) 0.087 0.071 +/- 20.3% Benzene (mg/L) <0.0005 <0.0005 0% MtBE (mg/L) 0.00073 0.00089 +/- 19.8% TBA (mg/L) <0.005 <0.005 0% Analyte Sample # Sample # % Difference MW-27 QCDUP-4 TPHg (mg/L) <0.05 <0.05 0% TPHd (mg/L) 0.12 0.15 +/- 22.2% TPHo (mg/L) 0.10 0.11 +/- 9.5% Benzene (mg/L) <0.0005 <0.0005 0% MtBE (mg/L) <0.0005 <0.0005 0% TBA (mg/L) <0.005 <0.005 0% 2.4.2.7 General Laboratory Notes The laboratory validation issues are consistent with the deep zone quality assurance and quality control. Each set of issues corresponds directly with the denoted report. All laboratory reports are included in Appendix D. Validation issues with report number 78189: The MRL for chloromethane was raised in samples collected from well MW-59 due to the presence of an interfering compound. Validation issues with report number 78379: The matrix spike duplicate associated with sample MW-51 for the analyte benzene was outside of the stated QC limits for percent recovery. This may indicate a possible bias for the reporting accuracy. The laboratory control spike percent recovery and relative percent difference values were within QC limits indicating accuracy and precision in reporting; therefore, the reported values are considered valid. IA-Fidewater7W Stockton(P2A)\QMRs\2011\3Q11\3011 QSSR QRSR QMR Stockton_FINAL.doc 2.11