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L & M OPERABLE UNIT- FIRST QUARTER 2012 SITE STATUS, REMEDIAL SUMMARY, <br />AND GROUNDWATER MONITORING REPORT <br />Groundwater Monitoring and Sampling <br />April 30, 2012 <br />I:\Tidewater\TW Stockton (P2A)\QMRs\2012\1Q12\1Q12 QSSR QRSR QMR Stockton_FINAL.doc 2.6 <br />2.3.2.6 Quality Assurance/Quality Control Samples <br />TPHd, TPHo, TPHg, BTEX compounds, fuel oxygenates (MtBE, TAME, DIPE, EtBE, TBA), and <br />VOCs were not detected at or above laboratory MRLs within Stantec’s equipment blanks <br />QCEB-1-RG, QCEB-1-PV, QCEB-2-RG, QCEB-2-PV, and QCEB-3-RG, with the exception of a <br />toluene detection slightly above the MRL in QCEB-2-RG (0.00056 mg/L). <br />Duplicate samples QCDUP-1, QCDUP-3, and QCDUP-7 were collected from L&M OU shallow <br />zone wells MW-34, MW-21, and MW-25, respectively, during 1Q12 sampling event. A <br />comparison of the samples is shown below. <br />Analyte Sample # <br />MW-34 <br />Sample # <br />QCDUP-1 % Difference <br />TPHg (mg/L)<0.05 <0.05 0% <br />TPHd (mg/L)0.057 <0.05 ~13.1% <br />TPHo (mg/L)<0.05 <0.05 0% <br />Benzene (mg/L)<0.0005 <0.0005 0% <br />MtBE (mg/L)<0.0005 <0.0005 0% <br />TBA (mg/L)<0.005 <0.005 0% <br />Analyte Sample # <br />MW-21 <br />Sample # <br />QCDUP-3 % Difference <br />TPHg (mg/L)<0.05 <0.05 0% <br />TPHd (mg/L)0.77 0.80 +/-3.8% <br />TPHo (mg/L)<0.05 <0.05 0% <br />Benzene (mg/L)<0.0005 <0.0005 0% <br />MtBE (mg/L)<0.0005 <0.0005 0% <br />TBA (mg/L)<0.005 <0.005 0% <br />Analyte Sample # <br />MW-25 <br />Sample # <br />QCDUP-7 % Difference <br />TPHg (mg/L)<0.05 <0.05 0% <br />TPHd (mg/L)<0.05 <0.05 0% <br />TPHo (mg/L)<0.05 <0.05 0% <br />Benzene (mg/L)<0.0005 <0.0005 0% <br />MtBE (mg/L)<0.0005 <0.0005 0% <br />TBA (mg/L)<0.005 <0.005 0% <br />A percent difference for TPHd results associated with sample MW-34 and QCDUP-1 is <br />estimated at about 13.1 percent (based on MDL of 0.05 mg/L) during 1Q12 due to QCDUP-1 <br />being below the MDL.