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Stantec <br /> L & M OPERABLE UNIT- FOURTH QUARTER AND ANNUAL 2012 SITE STATUS, <br /> REMEDIAL SUMMARY, AND GROUNDWATER MONITORING REPORT <br /> Summary of 2012 Annual Monitoring and Sampling <br /> February 1, 2013 <br /> the central part of the Site, groundwater flow direction was to the west. In the eastern part of <br /> the Site, groundwater flow direction was to the northeast. During the 2Q12, 3Q12, and 4Q12, <br /> groundwater flow direction was to the northeast and north-northwest. The hydraulic gradients <br /> across the C-Zone wells ranged between 0.0009 ft/ft (1Q12 and 2Q12) and 0.003 ft/ft (4Q12). <br /> 5.4 D-ZONE TRENDS IN GROUNDWATER GRADIENT <br /> During 2012, groundwater elevations in the D-Zone wells ranged between 6.70 feet below MSL <br /> (MW-70, 4Q12) and 5.21 feet below MSL (MW-73, 2Q12). The highest groundwater elevations <br /> were measured during 2Q12. The lowest groundwater elevations were generally measured <br /> during 4Q12. Groundwater elevation contour maps for the 1Q12, 2Q12, and 3Q12 are included <br /> in Appendix K <br /> Groundwater flow direction in D-Zone wells gradually shifted flow direction from east-northeast, <br /> during 1Q12, to north-northeast during 2Q12, and north during 3Q12 and 4Q12. The <br /> groundwater flow direction in D-Zone wells during 2012 is consistent with historical data. The <br /> hydraulic gradients across the D-Zone wells ranged between 0.0004 ft/ft (1Q12 and 3Q12) and <br /> 0.0008 ft/ft (2Q12). <br /> 5.5 SHALLOW AND DEEP ZONE SPH AND TRENDS <br /> Sheen or measurable SPH was observed in 11 of a possible 57 shallow and deep zone wells <br /> across the Site during 2012. <br /> 5.5.1 Shallow Zone Trends <br /> During 2012, sheen or measurable SPH was observed in wells 2AMW-13, 2AMW-14, and <br /> MW-19. In the shallow wells, sheen and SPH product was mainly observed in the L&M OU <br /> area. Additional product was observed on the northern section of the L&M OU, just south of <br /> Water Front Towers' parking lot. <br /> Wells 2AMW-13, 2AMW-14, and MW-19 contained sheen during all four quarters in 2012. No <br /> measurable SPH thickness was present for 2012 in all shallow zone wells. <br /> SPH removal activities were conducted on shallow zone wells 2AMW-13 and MW-19 during all <br /> four quarters of 2012. SPH thickness appears to be stable in each of these wells following <br /> removal activities. <br /> 5.5.2 Deep Zone Trends <br /> During 2012, sheen or measurable SPH was observed in wells MW-17, MW-43, MW-46 through <br /> MW-50, and MW-52. In the deep zone wells, sheen and SPH product was mainly observed on <br /> the northern section of the L&M OU and south of the Water Front Towers' parking lot. In the off <br /> Site deep zone wells, sheen was observed in the Delta View Apartments in well MW-46 only. <br /> I:\Tidewater\TW Stockton(P2A)\QMRs\2012\4Q12-Ann ual\4Q12 and Annual QSSR QRSR QMR Stockton_FINAL.doc 5.2 <br />