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Stantec <br /> L & M OPERABLE UNIT- FOURTH QUARTER AND ANNUAL 2010 SITE STATUS, <br /> REMEDIAL SUMMARY, AND GROUNDWATER MONITORING REPORT <br /> Groundwater Monitoring and Sampling <br /> January 31, 2011 <br /> gradients summarized in Table 9. The D-Zone groundwater elevation contour map for the <br /> October 18, 2010 monitoring event is included as Figure 24. <br /> 2.6.2 D-Zone Groundwater Quality Data <br /> During 4Q10, groundwater samples were collected from eight D-Zone wells between October <br /> 18 and 21, 2010 (Table 1). Groundwater analytical results are presented in Tables 4 through 7, <br /> and summarized below. TPHg, TPHd, TPHo, benzene, MtBE, and TBA isoconcentration <br /> contour maps are included as Figures 25 through 30, respectively. The certified laboratory <br /> analytical reports for the groundwater sampling event conducted for the L&M OU are included in <br /> Appendix C. <br /> 2.6.2.1 Separate Phase Hydrocarbons <br /> During 4Q10, measurable SPH or SPH-sheen was not observed in any D-Zone wells. <br /> 2.6.2.2 Petroleum Hydrocarbons and Fuel Oxygenates <br /> TPHg, TPHd, TPHo, and Fuel Oxygenates with concentrations at or above the MRLs are <br /> summarized below. <br /> Number of Number ofMinimum Detected Maximum Detected <br /> D-Zone <br /> Constituents Detections Wells Concentration in mg/L Concentration in mg/L <br /> above the MRL Analyzed (Well ID) (Well ID) <br /> TPHg 4 8 0.21 (MW-72) 1.0 (MW-70) <br /> TPHd 7 8 0.064 (MW-73) 1.9 (MW-55) <br /> TPHo 2 8 0.075 (MW-69) 0.094 (MW-68) <br /> Benzene 3 8 0.0005 (MW-68) 0.22 (MW-70) <br /> Toluene 1 8 -- 0.0056 (MW-70) <br /> Ethylbenzene 1 8 -- 0.0011 (MW-70) <br /> Total Xylenes 1 8 -- 0.0072 (MW-70) <br /> MtBE 1 8 -- 0.0015 (MW-55) <br /> TBA 2 8 0.013 (MW-71) 0.025 (MW-55) <br /> Definitions: <br /> mg/L = Milligrams per liter <br /> MRL = Method reporting limit <br /> MtBE= Methyl tertiary butyl ether <br /> TBA = Tertiary butyl alcohol <br /> TPHd = Total petroleum hydrocarbons as diesel <br /> TPHg = Total petroleum hydrocarbons as gasoline <br /> TPHo = Total petroleum hydrocarbons as motor oil <br /> -- = Not applicable <br /> I:\Tidewater\TW Stockton(Parcel 2A-0415)\Reports\QMR\2010\4010-Annual\4Q10 and Annual QSSRQRSRQMR Stockton_F I NAL.doc 2.15 <br />