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Stantec L & M OPERABLE UNIT- FOURTH QUARTER AND ANNUAL 2012 SITE STATUS, REMEDIAL SUMMARY, AND GROUNDWATER MONITORING REPORT Groundwater Monitoring and Sampling February 1, 2013 Number of Number ofMinimum Detected Maximum Detected C-Zone Constituents Detections Wells Concentration in mg/L Concentration in mg/L above the MRL Analyzed (Well ID) (Well ID) TPHg 4 7 0.35 (MW-65) 3.1 (MW-66) TPHd 5 7 0.14 (MW-63) 2.5 (MW-54) TPHo 5 7 0.095 (MW-66) 1.1 (MW-67) Benzene 3 7 0.00086 (MW-64) 0.013 (MW-66) Toluene 2 7 0.00065 (MW-54) 0.0043 (MW-66) Ethylbenzene 1 7 --- 0.0011 (MW-66) Total Xylenes 3 7 0.0012 (MW-64) 0.012 (MW-66) MtBE 2 7 0.003 (MW-54) 0.0088 (MW-64) TBA 2 7 0.028 (MW-64) 0.056 (MW-54) Definitions: ID = Identification mg/L = Milligrams per liter MRL = Method reporting limit MtBE= Methyl tertiary butyl ether TBA = Tertiary butyl alcohol TPHd = Total petroleum hydrocarbons as diesel TPHg = Total petroleum hydrocarbons as gasoline TPHo = Total petroleum hydrocarbons as motor oil --- = Not applicable 2.5.2.3 Quality Assurance/Quality Control Samples Duplicate sample QCDUP-3 was collected from L&M OU C-Zone well MW-62 during 4Q12 sampling event. A comparison of the samples is shown below. Analyte Sample # Sample # % Difference MW-62 QCDUP-3 TPHg (mg/L) <0.05 <0.05 0% TPHd (mg/L) 0.27 0.29 +/-7.1% TPHo (mg/L) 0.55 0.44 +/-22.2% Benzene (mg/L) <0.0005 <0.0005 0% MtBE (mg/L <0.0005 <0.0005 0% TBA (mg/L) <0.005 <0.005 0% A RPD for TPHo is estimated at 22.2 percent, during 4Q12. The RPD value for TPHo is greater than the recommended range of RPD (20 percent) for QC purposes. This may indicate a possible bias for reproducibility and precision. The TPHo analytical results are within historical values; therefore, the reported values are not anticipated to be affected. I:\Tidewater\TW Stockton(P2A)\QMRs\2012\4Q12-Ann ual\4Q12 and Annual QSSR QRSR QMR Stockton_FINAL.doc 2.9