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GEOTECHNICAL STUDY SUMMARY PROPOSED SAFEWAY FUEL CENTER 6425 PACIFIC AVENUE STOCKTON, CALIFORNIA The following report was prepared for Safeway, Inc. for the proposed Safeway Fuel Center to be located on 6425 Pacific Avenue in Stockton, California. Based on our geotechnical study, it is our opinion that the site may be developed for the proposed project. The contents of this report have been briefly summarized below for your convenience, however, the use of the summarized information without first reviewing the entire contents of the following report is not recommended. Based on our geotechnical study, we present the following summarized discussions and/or recommendations: SUBSURFACE CONDITIONS Fill was not encountered in the borings at the time of drilling. There may be fill in areas beyond or between our exploratory borings. In general, the native soils consisted of medium stiff to very stiff silty clay and dense clayey sand. Laboratory testing indicates that the near -surface soils have a high expansion potential. Groundwater was not encountered in borings at the time of drilling. We expect groundwater levels to fluctuate due to variations in rainfall, groundwater recharge, and site conditions. SITE PREPARATION Laboratory test results indicate the near -surface clayey soils are highly expansive and could be subject to movements with increased moisture content. These near -surface soils are not the best material for support of foundations, floor slabs, and exterior flatwork/sidewalks in their present state. To help reduce the potential for heaving clayey soils, we recommend these soils be over -excavated a minimum of 2 feet below the planned footing elevation for the convenience store area, moisture -conditioned, and recompacted in the foundation area and at least 5 feet beyond the structure and exterior flatwork/sidewalk areas in plan view, if practicable. The depth of over -excavation may be reduced by the depth of engineered fill placed at the site. Deeper sub - excavation may be required depending on soil conditions encountered during grading. Figure 8, Foundation Materials Under Building, presents the details for over -excavating and replacing the soil with compacted, engineered fill within the building limits. Compaction recommendations are discussed in Section 6.1.4 Fill Placement and Compaction. To help reduce the expansion and shrinkage potential of the clayey soil and to provide improved support for floor slabs, and exterior flatwork, we recommend the supporting soils be a minimum of 12 inches of non - expansive compacted fill, Class 4 material, lime -treated fill, or an approved equivalent placed on moisture - conditioned, compacted fill. The non -expansive fill should extend at least 5 feet beyond the building pad area and, where practicable, and/or 2 feet beyond exterior flatwork, whichever is greater. Additional recommendations are discussed in Section 6.1.4 Fill Placement and Compaction. On-site soil generated by site grading may be used as structural fill provided the soil is free of deleterious and organic materials and is approved for use as fill by our representative. The on-site soils should be moisture - conditioned, and compacted to a minimum of 90 percent relative compaction at a minimum of 2 percent over the optimum moisture content according to the latest ASTM test methods and procedures. All import fill to be placed must be compacted to a minimum relative compaction of 90 percent of the maximum dry density and moisture -conditioned to a minimum of 2 percent over the optimum moisture content according to ASTM test methods. For pavement areas, the upper 12 inches of subgrade soils should be scarified, moisture -conditioned as necessary, and recompacted to a minimum of 95 percent relative compaction. 6aKorbmacher Engineering, Inc.