1809 HOLBROOK AVE 2018-01-02 MF Import

Terhune Homes, Inc. JN 99028 February 25, 1999 Page 3 review would be additional work beyond the current scope of work for this study, and it may include revisions to our recommendations to accommodate site, development, and geotechnical constraints that become more evident during the review process. Conventional Foundations The proposed structure can be supported on conventional continuous and spread footings bearing on undisturbed, competent, native, silty sand, or on structural fill placed above this competent, native soil. See the later sub -section entitled General Earthwork and Structural Fill for recommendations regarding the placement and compaction of structural fill beneath structures. Adequate compaction of structural fill should be verified with frequent density testing during fill placement. We recommend that continuous and individual spread footings have minimum widths of 12 and 16 inches, respectively. They should be bottomed at least 18 inches below the lowest adjacent finish ground surface. The downslope perimeter and deck footings should be placed at least 5 feet below the existing grade. 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. Depending on the final site grades, some overexcavation may be required below the footings to expose rompetert, 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 dnd 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. An allowable bearing pressure of 2,000 pounds per square foot (psf) is appropriate for footings supported on competent, native soil. A one-third increase in this design bearing pressure 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 up to 5 feet in thickness, will be about one-half inch. 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 structural fill. We recommend using the following design values for the foundation's resistance to lateral loading: Parameter Design Value Coefficient of Friction 0.40 Passive Earth Pressure 300 pcf Where: (i) pcf is pounds per cubic fool, and (it) passive earth pressure is computed using the equivalent fluid density. GEOTECH CONSULTANTS, INC. fG