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L & M OPERABLE UNIT-THIRD QUARTER 2013 SITE STATUS, REMEDIAL SUMMARY, <br /> AND GROUNDWATER MONITORING REPORT <br /> Groundwater Monitoring and Sampling <br /> November 1, 2013 <br /> 2.4 THIRD QUARTER 2013 B-ZONE GROUNDWATER RESULTS <br /> 2.4.1 B-Zone Groundwater Gradient <br /> B-Zone groundwater elevations at the Site ranged from 5.33 ft below MSL (MW-59) to 2.67 ft <br /> above MSL (MW-44; Table 3, Table 4, and Figure 10). Groundwater flow direction and <br /> gradient during 3Q13 in the B-Zone ranged from north-northwest to the northeast at an average <br /> gradient of 0.013 and 0.011 ft/ft, respectively (Figure 10). The current gradient flow and <br /> direction is consistent with previous quarters. Historic groundwater flow direction and gradient <br /> data is summarized in Table 6. Vertical gradient data is summarized in Table 7. <br /> 2.4.2 B-Zone Groundwater Analytical Data <br /> During 3Q13, groundwater samples were collected from 13 B-Zone wells. Groundwater <br /> analytical results are summarized below and included in Table 3 and Table 4. TPHg, TPHd, <br /> TPHo, benzene, MTBE, and TBA isoconcentration contour maps are included as Figure 11 <br /> through Figure 16, respectively. The certified laboratory analytical reports including laboratory <br /> validation sheets for the groundwater sampling event conducted for the L&M OU are included in <br /> Appendix E. <br /> 2.4.2.1 Separate Phase Hydrocarbons <br /> During 3Q13, sheen was observed in five wells (MW-17, MW-46 through 48, and MW-52). <br /> Separate phase hydrocarbons were reported in three site wells (MW-43, MW-49, and MW-50). <br /> SPH thicknesses for B-Zone wells are summarized below. <br /> Well Identification SPH Thickness <br /> (feet) <br /> MW-43 0.40 <br /> MW-49 4.73 <br /> MW-50 31.20 <br /> 2.4.2.2 Petroleum Hydrocarbons and Fuel Oxygenates <br /> TPHg, TPHd, TPHo, and Fuel Oxygenates with reported concentrations at or above the <br /> laboratory MRLs are summarized on the following table. <br /> Number of Number of Minimum Detected Maximum Detected <br /> B-Zone <br /> Constituents Detections Concentration in mg/L Concentration in mg/L <br /> Wells <br /> above the MRL final Wells <br /> (Well ID) (Well ID) <br /> TPHg 2 13 0.36 (MW-42) 2.1 (MW-59) <br /> TPHd 12 13 0.052 (MW-57) 0.54 (MW-60) <br /> 5tantec 2.5 <br />