ARCHIVED REPORTS_FOURTH QUARTER AND ANNUAL 2010 SITE STATUS, REMEDIAL SUMMARY, AND GROUNDWATER MONITORING REPORT

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Stantec L & M OPERABLE UNIT- FOURTH QUARTER AND ANNUAL 2010 SITE STATUS, REMEDIAL SUMMARY, AND GROUNDWATER MONITORING REPORT Summary of 2010 Annual Monitoring and Sampling January 31, 2011 Groundwater flow directions in C-Zone wells were consistent in 2010. During 2Q10 and 3Q10, groundwater flow direction was observed in two sections of the site (north and south during 2Q10, and east and west during 3Q10). Along the northern portion of the site, groundwater flow direction was to the east-southeast (2Q10). In the southern part of the site, groundwater flow direction was to the northeast (2Q10). In the eastern part of the site, groundwater flow direction was to the northeast (3Q10). In the western part of the site, groundwater flow direction was to the northwest (3Q10). During 1Q10, groundwater flow direction was to the east-northeast. During 4Q10, groundwater flow direction was to the northwest. The hydraulic gradients across the C-Zone wells ranged between 0.002 ft/ft (2Q10 and 3Q10) and 0.005 ft/ft (4Q10). 5.4 D-ZONE TRENDS IN GROUNDWATER GRADIENT During 2010, groundwater elevations in the D-Zone wells ranged between 8.62 feet below MSL (MW-55, 4Q10) and 5.81 feet below MSL (MW-70, 2Q10). The highest groundwater elevations were measured during 2Q10. The lowest groundwater elevations were generally measured during 4Q10. Groundwater elevation contour maps for the 1010, 2Q10, and 3Q10 are included in Appendix I During 1Q10 and 2Q10, groundwater flow directions in D-Zone wells were generally to the east. During 3Q10, groundwater flow direction was observed in two sections of the site (east and west). In the eastern part of the site, groundwater flow direction was to the northeast. In the western part of the site, groundwater flow direction was to the northwest. Groundwater flow direction was to the north during 4Q10. The hydraulic gradients across the D-Zone wells ranged between 0.0009 ft/ft (1Q10 and 3Q10) and 0.003 ft/ft (3Q10). 5.5 SHALLOW AND DEEP ZONE SPH AND SHEEN TRENDS Sheen or measurable SPH was observed in 24 of a possible 75 shallow and deep zone wells across the Site during 2010. 5.5.1 Shallow Zone Trends During 2010, sheen or measurable SPH was observed in wells 2AMW-13, 2AMW-14, MW-19, and DPE-1 through DPE-13. In the shallow wells, sheen and SPH product was mainly observed in the DPE well area. Additional product was observed on the northern section of the L&M OU, just south of Water Front Towers' parking lot. Wells 2AMW-13, 2AMW-14, DPE-1 through DPE-4, DPE-7, and DPE-10 through DPE-13 contained sheen during all four quarters in 2010. Well MW-19 contained sheen during 2Q10, 3Q10, and 4Q10 only. Wells DPE-6, DPE-9, and DPE-9 contained SPH during 1Q10, and contained sheen during 2Q10, 3Q10, and 4Q10. DPE-5 contained SPH during 1 Q10 and 2Q10, and contained sheen during the 3Q10 and 4Q10. The highest observed SPH thickness for 2010 was in DPE-6 (0.17 ft) during the 1Q10. I:\Tidewater\TW Stockton(Parcel 2A-0415)\Reports\QMR\2010\4010-Annual\4Q10 and Annual OSSRQRSRQMR Stockton_FINAL.doc 5.2