SITE INFORMATION AND CORRESPONDENCE

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Appendix A: Summary of Previous Environmental Activities • Boring SB-37 south of and midway between SB-2 and SB-3; • Boring SB-38 south of SB-6; • Borings SB-39 and SB40 diagonally southwest and southeast of SB-8; • Boring SB-41 south and midway between SB-11 and SB-12; • Boring SB-42 south of SB-19; • Boring SB43 south of SB-23; • Boring SB-44 south of SB-25 (Caledron's General Store property); and • Boring SB45 southeast of SB-33 within the area occupied by a storm-water basin. SOIL AND GROUNDWATER INVESTIGATION REPORT 3. In March 2007,borings SB-37 through SB-41 were advanced to total depths ranging from 24 to 32 feet bgs to define the extent of affected soil and groundwater at the site, Soil sample analytical results were at non-detect levels and less than Preliminary Remediation Goals and Environmental Screening Levels(ESLs)_ Groundwater was encountered between 9 to 16 feet bgs. Groundwater analytical results were compared to the lowest,most conservative ESL and Water Quality Objective(WQO) concentrations for delineation purposes. Groundwater sample analytical results were less than WQOs and ESLs,with the following exceptions: • Total petroleum hydrocarbons quantified as diesel: SB-37 (100 micrograms per liter [gg/L]), SB-38 (140 gg/L), SB-39(160 gg/L), SB-40 (330 gg/L), and SB-41 (330 gg/L); and • Benzo(g,h,i)perylene: SB-39(0.40 gg/L). SAIC reviewed the findings of this and previous site investigations along the West Byron Road corridor and concluded and recommended the following: • The up-gradient extent of several affected areas was delineated by borings SB-37 through SB-41. • Proposed borings SB42, SB-43,and SB-45 should be repositioned and advanced to fully delineate the up-gradient extent of affected soil and groundwater. • The up-gradient extent of soil and groundwater was defined at monitoring wells MW-2 I and MW-3 during a site investigation at the Calderon's General Store property`'; therefore, advancement of proposed step-out boring SB-44 south of boring SB-25 suggested in SAIC's 2004 work plan was not necessary. • The proposed apartment complex at the northeast corner of Lammers Road and Feteira Way in Tracy was unlikely to be impacted by affected soil and groundwater from the former Old Valley Pipeline,as it is up gradient and approximately 1,300 feet away. I 3. SAIC,2008. Soil and Groundwater Investigation Report, Tracy Byron Road Project, Tracy,San Joaquin Count};California_ I May. 4. Geological Audit Services,1995. Site Srnnmary Report, Calderon's General Store-12750 West Byron Road,Tracy, California. March. A-2 SAIC I