3315 BROADWAY 2017 HOPEWORKS STATION 2 Geotech Report 2022-10-25

Hope Works Social Enterprises JN 17298 July 12, 2017 Page 7 CONVENTIONAL FOUNDATIONS As is noted in the General section of this report, the proposed structure can be supported on conventional continuous and spread footings bearing on undisturbed, native soil, or on structural fill placed above this competent native soil. See the section entitled General Earthwork and Structural Fill for recommendations regarding the placement and compaction of structural fill beneath structures. The following allowable bearing pressures are appropriate for footings constructed according to the above recommendations: ALLOWABLE OWABLE BEARING CONDITION BEARING PRESSURE Placed directly on competent, 2,000 psf native, medium-dense soil Placed directly on competent, 5,000 psf native, dense slightly silty sand or on structural fill as noted in the General section Where:psf is Pounds per Square Foot. Depending on the final site grades, overexcavation may be required below the footings to expose competent native soil. Unless lean concrete is used to fill an overexcavated hole, the overexcavation must be at least as wide at the bottom as the sum of the depth of the overexcavation and the footing width. For example, an overexcavation extending 2 feet below the bottom of a 2-foot-wide footing must be at least 4 feet wide at the base of the excavation. If lean concrete is used, the overexcavation need only extend 6 inches beyond the edges of the footing. A typical detail for overexcavation beneath footings is attached as Plate 8. We recommend that continuous and individual spread footings have minimum widths of 16 and 24 inches, respectively. Exterior footings should also be bottomed at least 18 inches below the lowest adjacent finish ground surface for protection against frost and erosion. The local building codes should be reviewed to determine if different footing widths or embedment depths are required. Footing subgrades must be cleaned of loose or disturbed soil prior to pouring concrete. Depending upon site and equipment constraints, this may require removing the disturbed soil by hand. A one-third increase in these design bearing pressures may be used when considering short-term wind or seismic loads. For the above design criteria, it is anticipated that the total post-construction settlement of footings founded on competent native soil, or on structural fill, will be about one inch, with differential settlements on the order of one half-inch in a distance of 50 feet along a continuous footing with a uniform load. Lateral loads due to wind or seismic forces may be resisted by friction between the foundation and the bearing soil, or by passive earth pressure acting on the vertical, embedded portions of the foundation. For the latter condition, the foundation must be either poured directly against relatively level, undisturbed soil or be surrounded by level, well-compacted fill. GEOTECH CONSULTANTS,INC.