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Project No. JB -314 24 March 2003 Page 5 structures should be designed to meet current Uniform Building Code (UBC) requirements to limit potential damage from ground shaking. 6.0 RECOMMENDATIONS 6.1 Earthwork 6.1.1 General As previously stated, final grading plans were not available during preparation of this report. We recommend that final grading plans be reviewed by our office prior to starting the grading operations. As previously discussed, our 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 the kiosk subgrade soils be over -excavated a minimum of 2 feet below the proposed footing elevation for the building areas, 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. 6.1.2 Site Clearing All grading must be observed by our representative. It is especially important that our representative be present during the demolition, stripping and scarification process to observe whether undesirable materials are encountered. Loose, soft, uncontrolled fill, or disturbed native soils must be removed from all structural areas, beneath adjacent walks and slabs, beneath areas to receive fill, and beneath areas to be paved. Excavations must extend at least 5 feet beyond the Korbmacher Engineering. Inc.