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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 B-Zone Constituents Detections Wells Concentration in mg/L Concentration in mg/L above the MRL Analyzed (Well ID) (Well ID) TPHg 4 6 0.059 (MW-51) 2.3 (MW-59) TPHd 6 6 0.32 (MW-16) 0.95 (MW-59) TPHo 5 6 0.063 (MW-59) 0.84 (MW-60) Benzene 1 6 --- 0.0024 (MW-42) Definitions: ID = Identification mg/L = Milligrams per liter MRL = Method reporting limit TPHd = Total petroleum hydrocarbons as diesel TPHg = Total petroleum hydrocarbons as gasoline TPHo = Total petroleum hydrocarbons as motor oil --- = Not applicable 2.4.2.3 Quality Assurance/Quality Control Samples Duplicate samples QCDUP-2 was collected from L&M OU B-Zone well MW-42, during 4Q12 sampling event. A comparison of the samples is shown below. Analyte Sample # Sample # oda Difference MW-42 QCDUP-2 TPHg (mg/L) 0.36 0.38 +/-5.4% TPHd (mg/L) 0.63 0.65 +/-3.1% TPHo (mg/L 0.4 0.46 +/- 14.0% Benzene (mg/L) 0.0024 0.0025 +/-4.1% MtBE (mg/L) <0.0005 <0.0005 0% TBA (mg/L) <0.005 <0.005 0% 2.4.2.4 General Laboratory Notes The laboratory validation issues are consistent with the B-Zone quality assurance and quality control. No issues were report for the B-Zone in the reports. All laboratory reports are included in Appendix E. 2.5 FOURTH QUARTER 2012 C-ZONE GROUNDWATER RESULTS 2.5.1 C-Zone Groundwater Gradient Data C-Zone groundwater elevations at the Site ranged from 6.50 ft below MSL in wells MW-62 and MW-64 to 5.96 ft below MSL in well MW-66 (Table 3 and Figure 17). Groundwater gradient I:\Tidewater\TW Stockton(P2A)\QMRs\2012\4Q12-Ann ual\4Q12 and Annual QSSR QRSR QMR Stockton_FINAL.doc 2.7