905 80TH ST SW MTORRES AMERICA 2018-09-18

February 22,2016 Project No. T-7364 4.5 Foundations, The building may be supported on conventional spread footing foundations bearing on competent native soils or on structural fill placed above competent native soils. Foundation subgrades should be prepared as recommended in Section 4.2 of this report. Perimeter foundations exposed to the weather should bear at a minimum depth of 1.5 feet below final exterior grades for frost protection. Interior foundations can be constructed at any convenient depth below the floor slab. Foundations supported on,an undisturbed subgrade consisting of the native, dense to very dense unweathered till can be dimensioned for a net allowable bearing capacity of 5,000 pounds per square foot(psf). The grading plan indicates that the north-central portion of the proposed building will be underlain by structural fill. Foundation elements supported by structural fill should be dimensioned for an allowable bearing capacity of 3,000 psf. For short-term loads, such as wind and seismic, a one-third increase in this allowable capacity can be used. With structural loading as anticipated and this bearing stress applied,estimated total settlements are less thanone-inch. For designing foundations to resist lateral loads, a base friction coefficient of 0.35 can be used. Passive earth pressures acting on the side of the footing can also be considered. We recommend calculating this lateral resistance using an equivalent fluid weight of 350 pounds per cubic foot(pet) We recommend not including the upper 12 inches of soil in this computation because it can be affected by weather or disturbed by future grading activity. This value assumes the foundation will be constructed neat against competent native soil or backfilled with structural fill as described in Section 4.2 of this report. The values recommended include a safety factor of 1.5. 4.6 Lateral Earth Pressures for Below-Grade Walls The magnitude of earth pressure development on engineered retaining walls will partly depend on the quality of the wall backfill. We recommend placing and compacting wall backfill as structural fill as described in Section 4.2 of this report. To guard against hydrostatic pressure development, wall drainage must also be installed. A typical recommended wall drainage detail is shown on Figure 4. With wall backfill placed and compacted as recommended and drainage properly installed, we recommend designing unrestrained walls for an active earth pressure equivalent to a fluid weighing 35 pounds per cubic foot (pcf). For restrained walls, an additional uniform lateral pressure of 100 psf should be included. For evaluation of below-grade walls under seismic loading, an additional uniform lateral pressure equivalent to SH psf,where H is the height of the below-grade portion of the wall in feet, can be used. These values assume a horizontal backfill condition and that no other surcharge loading such as traffic,sloping embankments,or adjacent buildings will act on the wall. If such conditions will exist, then the imposed loading must be included in the wall design. Friction at the base of foundations and passive earth pressure will provide resistance to these lateral loads. Values for these parameters are given in Section 4.5 of this report. Page No. 9