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CORNERSTONE C. EARTH GROUP The vertical capacity of the piers may be designed based on an allowable skin friction of 500 psf for combined dead plus live loads based on a factor of safety of 2.0; dead loads should not exceed two-thirds of the allowable capacities. The allowable skin friction may be increased by one-third for wind and seismic loads. Frictional resistance to uplift loads may be developed along the pier shafts based on an ultimate frictional resistance of 600 psf; the structural engineer should apply an appropriate factor of safety (such as 1.5) to the ultimate uplift capacity. Total settlement of individual piers should not exceed % inch to mobilize static capacities and post-construction differential settlement between adjacent piers should not exceed'/, inch due to static loads. 7.3.2 Lateral Capacity Lateral loads exerted on the structure may be resisted by a passive resistance based on an ultimate equivalent fluid pressure of 450 psf acting against twice the projected area of piers below the grade beam, up to a maximum uniform pressure of 2,500 psf at depth. The upper 12 inches of soil should be neglected when determining lateral capacity. The structural engineer should apply an appropriate factor of safety to the ultimate passive pressures. 7.3.3 Construction Considerations The excavation of all drilled shafts should be observed by a Cornerstone representative to confirm the soil profile and observe that the piers are constructed in accordance with our recommendations and project requirements. The drilled shafts should be straight, dry, and relatively free of loose material before reinforcing steel is installed and concrete is placed. If perched ground water is encountered that cannot be removed from the excavations prior to concrete placement, the concrete should be placed using a tremie pipe, keeping the tremie pipe below the surface of the concrete to avoid entrapment of water in the concrete. Due to the loose nature of some of the cleaner sand layers, the use of temporary casing of each drilled shaft may be required if caving soil conditions are encountered. SECTION 8: CONCRETE SLABS AND PEDESTRIAN PAVEMENTS 8.1 EXTERIOR FLATWORK 8.1.1 Pedestrian Concrete Flatwork Exterior concrete flatwork subject to pedestrian and/or occasional light pickup loading should be at least 4 inches thick and supported directly upon subgrade prepared in accordance with the "Earthwork" recommendations of this report. Flatwork that will be subject to heavier or frequent vehicular loading should be designed in accordance with the recommendations in the "Vehicular Pavements" section below. To help reduce the potential for uncontrolled shrinkage cracking, adequate expansion and control joints should be included. Consideration should be given to limiting the control joint spacing to a maximum of about 2 feet in each direction for each inch of concrete thickness. Flatwork should be isolated from adjacent foundations or retaining walls Ponderosa Active Adult Community Page 20 132-2-1