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locations, these fill soils extend to depths of 21/2 to 3* feet. These fill soils should be removed in their entirety. It is also recommended that the overexcavation extend to a depth of at least 3 feet below proposed pad grade, and 3 feet below existing grade. Within the influence zones of the new foundations, the overexcavation should extend to a depth of at least 2 feet below proposed foundation bearing grade. The overexcavation should extend at least 5 feet beyond the building perimeter, and to an extent equal to the depth of new fill below the foundation bearing grade. If the proposed structure incorporates any exterior columns (such as for a building canopy or overhang) the overexcavation should also encompass these areas. The remedial grading activities within the proposed building area will require excavation near the east property line. Therefore, slot cutting techniques may be required in this area of the site, to remove the existing undocumented fill soils while providing adequate lateral support for the adjacent property. It is recommended that copies of the grading and foundation plans be provided to our office for review with regard to the need for specialized grading techniques in this area of the site. Following completion of the overexcavation, the subgrade soils within the building area should be evaluated by the geotechnical engineer to verify their suitability to serve as the structural fill subgrade, as well as to support the foundation loads of the new structure. This evaluation should include proofrolling and probing to identify any soft, loose or otherwise unstable soils that must be removed. Some localized areas of deeper excavation may be required if additional fill materials or loose, porous, or low density native soils are encountered at the base of the overexcavation. Based on conditions encountered at the exploratory boring locations, some zones of moist to very moist soils will be encountered at or near the base of the recommended overexcavation. Stabilization of the exposed overexcavation subgrade soils is expected to be necessary. Scarification and air drying of these materials may be sufficient to obtain a stable subgrade. However, if highly unstable soils are identified, and if the construction schedule does not allow for delays associated with drying, mechanical stabilization, usually consisting of coarse crushed stone or geotextile, could be necessary. In this event, the geotechnical engineer should be contacted for supplementary recommendations. After a suitable overexcavation subgrade has been achieved, the exposed soils should be scarified to a depth of at least 12 inches, and moisture conditioned to at least 2 to 4 percent above optimum moisture content, and recompacted to at least 90 percent of the ASTM D-1557 maximum dry density. The previously excavated soils may then be replaced as compacted structural fill. Treatment of Existing Soils: Proposed Concrete Flatwork Areas Subgrade preparation in the new flatwork areas should initially consist of removal of all soils disturbed during stripping and demolition operations. The geotechnical engineer should then evaluate the subgrade to identify any areas of additional unsuitable soils. The subgrade soils should then be scarified to a depth of 12+ inches, moisture conditioned to 2 to 4 percent above optimum, and recompacted to at least 90 percent of the ASTM D-1557 maximum dry density. 1â€¢:F i . SOUTHERN G&M Convenience Store #72 - Santa Ana, CA CALIFORNIA Project No. 16G 123-1R GEOTECHNICAL Page 16