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6.4 Construction Considerations Excavation Considerations The near-surface soils at this site generally consist of sands and silts. These materials may be subject to caving within shallow excavations. Where caving occurs within shallow excavations, flattened excavation slopes may be sufficient to provide excavation stability. Deeper excavations may require some form of external stabilization such as shoring or bracing. Maintaining adequate moisture content within the near-surface soils will improve excavation stability. Temporary excavation slopes should be no steeper than 2h: lv. All excavation activities on this site should be conducted in accordance with Cal-OSHA regulations. Remedial grading for the proposed structure will require excavation immediately adjacent to the east property line. The contractor should take all necessary provisions to protect any improvements on the adjacent properties. If caving is encountered during remedial grading activities, slot cutting or shoring may be required. Typically, A-B-C slot cuts on 6 to 8-foot centers are suitable to maintain excavation stability. The geotechnical engineer should observe the conditions and determine the appropriate slot cutting procedures at the time of site grading. Moisture Sensitive Subarade Soils Some of the near-surface soils possess appreciable silt and clay content and will become unstable if exposed to significant moisture infiltration or disturbance by construction traffic. In addition, based on their granular content, some of the on-site soils will be susceptible to erosion. Therefore, the site should be graded to prevent ponding of surface water and to prevent water from running into excavations. As discussed in Section 6.3 of this report, unstable subgrade soils will likely be encountered at the base of the overexcavation within the proposed building area. The extent of unstable subgrade soils will to a large degree depend on methods used by the contractor to avoid adding additional moisture to these soils or disturbing soils which already possess high moisture contents. If grading occurs during a period of relatively wet weather, an increase in subgrade instability should also be expected. If unstable subgrade conditions are encountered, it is recommended that only track mounted vehicles be used for fill placement and compaction. If the construction schedule dictates that site grading will occur during a period of wet weather, allowances should be made for costs and delays associated with drying the on-site soils or import of a less moisture sensitive fill material. Grading during wet or cool weather may also increase the depth of overexcavation in the pad areas as well as the need for and or the thickness of the crushed stone stabilization layer, discussed in Section 6.3 of this report. '-11 CALIFORNIA 1 GEOTECHNICAL G&M Convenience Store # 72 - Santa Ana, CA Project No. 16G 123-1R Page 19