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 January 31, 2011 5.0 Summary of 2010 Annual Monitoring and Sampling 5.1 SHALLOW ZONE TRENDS IN GROUNDWATER GRADIENT During 2010, groundwater elevations in the shallow zone wells ranged between 5.67 feet below MSL (DPE-6, 4Q10) and 5.62 feet above MSL (MW-30, 2Q10). The highest groundwater elevations were generally measured during 2Q10. The lowest groundwater elevations were generally measured during the 1Q10 and 4Q10. Groundwater elevation contour maps for the 1Q10, 2Q10, and 3Q10 are included in Appendix I. Groundwater flow direction during 2010 was consistent across the shallow zone groundwater. Groundwater flow direction during 2010 was generally observed in two sections of the site (northeast and southwest). Along the northeast portion of the site, groundwater flow direction was generally to the south. In the southwestern part of the site, groundwater flow direction was generally to the east-northeast. The hydraulic gradients across the shallow zone wells ranged between 0.005 ft/ft (first quarter 2010; 1010) and 0.024 ft/ft (3Q10). 5.2 B-ZONE TRENDS IN GROUNDWATER GRADIENT During 2010, groundwater elevations in the B-Zone wells ranged between 7.61 feet below MSL (MW-47,1Q10) and 2.19 feet above MSL (MW-44, 2Q10). The highest groundwater elevations were generally measured during 2Q10. The lowest groundwater elevations were measured during the 1Q10 and 4Q10. Groundwater elevation contour maps for 1Q10, 2Q10, and 3Q10 are included in Appendix I. Groundwater flow direction during 2010 was generally consistent across the B-Zone groundwater. Groundwater flow direction during 2010 was generally observed in three to four sections of the Site (north, south, west, and central). Along the northern portion of the site, groundwater flow direction was generally to the south (2Q10, 3Q10, and 4Q10), and to the northwest (1Q10). In the southern part of the site, groundwater flow direction was generally to the east-northeast (1Q10) and east-southeast (3Q10 and 4Q10). In the western portion of the site, groundwater flow direction was generally to the north-northwest (2Q10, 3Q10, and 4Q10). In the central portion of the site, groundwater flow direction was generally to the northeast (1Q10, 2Q10, 3Q10, and 4Q10). The hydraulic gradients across the B-Zone wells ranged between 0.004 ft/ft (4Q10) and 0.023 ft/ft (1Q10). 5.3 C-ZONE TRENDS IN GROUNDWATER GRADIENT During 2010, groundwater elevations in the C-Zone wells ranged between 8.58 feet below MSL (MW-54, 4Q10) and 5.84 feet below MSL (MW-67, 2Q10). The highest groundwater elevations were generally measured during 2Q10. The lowest groundwater elevations were measured during the 1Q10 and 4Q10. Groundwater elevation contour maps for 1Q10, 2Q10, and 3Q10 are included in Appendix I. Iffidewater7W Stockton(Parcel 2A-0415)\Reports\QMR\2010\4010-Annual\4Q10 and Annual QSSRQRSRQMR Stockton_FINAL.doc 5.1