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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 2.5.2.4 General Laboratory Notes The laboratory validation issues are consistent with the C-Zone quality assurance and quality control. No issues were report for the C-Zone in the reports. All laboratory reports are included in Appendix E. 2.6 FOURTH QUARTER 2012 D-ZONE GROUNDWATER RESULTS 2.6.1 D-Zone Groundwater Gradient Data D-Zone groundwater elevations at the Site ranged from 6.70 ft below MSL in well MW-70 to 6.31 ft below MSL in well MW-73 (Table 3 and Figure 24). Groundwater gradient during 4Q12 in the D-Zone was calculated to the north with an approximate hydraulic gradient of 0.0005 ft/ft (Figure 24). The highest D-Zone groundwater elevation (6.31 ft below MSL) was reported in well MW-73, located in the Delta View Apartments, south of L&M OU area. Historical groundwater flow direction and gradient data are summarized in Table 5, and vertical gradients summarized in Table 6. The D-Zone groundwater elevation contour map for the October 15, 2012 monitoring event is included as Figure 24. 2.6.2 D-Zone Groundwater Quality Data During 4Q12, groundwater samples were collected from eight D-Zone wells between October 15 and 17, 2012 (Table 1). Groundwater analytical results are presented in Table 4, and summarized below. TPHg, TPHd, TPHo, benzene, MtBE, and TBA isoconcentration contour maps are included as Figures 25 through 30, respectively. The certified laboratory analytical reports for the groundwater sampling event conducted for the L&M OU are included in Appendix E. 2.6.2.1 Separate Phase Hydrocarbons During 4Q12, measurable SPH or SPH-sheen was not observed in any D-Zone wells. I:\Tidewater\TW Stockton(P2A)\QMRs\2012\4Q12-Ann ual\4Q12 and Annual QSSR QRSR QMR Stockton_FINAL.doc 2.10