4020 COLBY AVE Geotech Report 2018-01-02 MF Import

McDor.al.d�s Corporation }:-3G7G December 21, 1987 Fage 4 Foundations The propused structure may be supnorted on conventior�al continuous and spread foctings bearing on competent soils found at the proposed grade. Exterior footings should be bottomed at a minimum depth of twelve (12) inches below the lowest adjacent outside finish grade. Interior footings may be at a depth of twelve (12) inches below the top of the siab. Footings supported directly on competent native soils may be designed for a soil-bearing pressure of three thousand (3000) psf. Continuous and individual spread footings should have minimum widths of twelve (12) and eighteen (18) inches, respect- ively. A one-third increase in the above bearing pressures may be used when considerinq short term wind or seismic loads. For the above uesign criteria, it is anticipated that total settle- ments of footings founded on the native soil at depth will be about one-half inch. Almost all settlements should occur during construc- tion. Lateral l.oads due to wind or seismic forces may be resisted by friction between the foundation and the supporting compacted Fill subgrade or by passive earth pressure on the foundations. For the latter, the foundations must be poured "neat" aqainst the existing soil or backfilled with a compacted fill meeting the requirements of structural fi11. A coefficient of friction of 0.40 may be used between the structural foundation concrete and the supporting subgrade. The passive resistance of undisturbed natural soils and i well compacted fill may be taken as equal to the pressure of a fluid having a density of three hundred (300) pounds per cubic foot (pcf) . Tye above foundations considerations also apply to the signs planned for this project. We recommend that drains be placed around all perimeter footings. The drains should be constructed with a four-inch diameter per- forated rigid PVC pipe bedded and covered with free-draining gravel. The drains should have a positive gradient towards suitable dis- charge facilities. The footing drainage system should not be tied into the roof drainage system unti.l the drains are tightlined well away from the building. The footing excavation should be backfilled with granular soi� except for the top foot which shuuld be back- filled with a relatively impermeable soil such as silt, clay or topsoil. Alternatively, the surface can be sealed with asphalt or concrete pavements. Earth Consultants, Inc.