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L & M OPERABLE UNIT-THIRD QUARTER 2013 SITE STATUS, REMEDIAL SUMMARY, AND GROUNDWATER MONITORING REPORT Groundwater Monitoring and Sampling November 1, 2013 2.5.2.4 Quality Assurance/Quality Control Samples Duplicate sample QCDUP-5 was collected from well MW-64. A comparison of the samples is shown below. Analyte Sample # Sample # % Difference MW-64 QCDUP-3 TPHg (mg/L) 2 2 0% TPHd (mg/L) 1.2 1.1 +/- 8.7% TPHo (mg/L) 0.68 0.07 +/-2.9% Benzene (mg/L) 0.00051 0.00055 +/- 7.6% MTBE (mg/L) 0.013 0.013 0% TBA (mg/L) 0.021 0.020 +/-4.9% Analytical results were reported at the value, and therefore, the results can be considered valid. 2.5.2.5 General Laboratory Notes The laboratory validation issues are consistent with the C-Zone quality assurance and quality control. Each set of issues corresponds directly with the denoted report. Laboratory reports are included in Appendix E. Laboratory Validation, report number 85467: There was no observed validation issues with C-Zone monitoring wells. 2.6 THIRD QUARTER 2013 D-ZONE GROUNDWATER RESULTS 2.6.1 D-Zone Groundwater Gradient Data D-Zone groundwater elevations at the Site ranged from 5.94 ft below MSL (MW-74) to 5.09 ft below MSL (MW-55; Table 3, Table 4, and Figure 24). Groundwater gradient during 3Q13 was calculated to the south-southeast with an approximate hydraulic gradient of 0.002 ft/ft (Figure 24). Historic groundwater flow direction and gradient data is summarized on Table 6. Vertical gradient data is summarized on Table 7. 2.6.2 D-Zone Groundwater Analytical Data During 3Q13, groundwater samples were collected from eight D-Zone. Groundwater analytical results are summarized below and included on Table 3 and Table 4. TPHg, TPHd, TPHo, benzene, MTBE, and TBA isoconcentration contour maps are included as Figure 25 through Figure 30, respectively. The certified laboratory analytical reports including laboratory validation sheets are included in Appendix E. 5tantec 2.9