406 SE EVERETT MALL WAY BASE FILE 2018-01-02 MF Import

Auto Mall Associates May 16, 1986 E-2976 Page 4 Dn structural fill placed above competent native soils. Fill placed under footings should extend outwards from the edge of the footings at least a distance equal to the depth of the fill. �SSar 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 slab. Footings founded on very dense native till a-vy� soils may be designed for an allowable soil bearing capacity of lY six thousand (6000) pounds per square foot (psf). Footings bearing on structural fill or recompacted upper site soils should be designed for a hearing pressure of twenty five hundred (2500) psf. Continuous and individual spread footings should have minimum widths of twelve (12) and eighteen (18) inches, respectively. A one-third increase in the above bearing pressures may be used when considering short term wind or seismic loads. For the above design criteria, it is anticipated that total settlements of footings founded on dense till soils and on fills less than five feet thick will be about three-quarter inch, with differential settlements of one-half inch. Almost all settlements should occur during construction. If any continuous footings are located partially in cut and partially in fill, we recommend that the structural engineer consider adding additional reinforcement in the footings and footing walls near the cut -fill transition line to minimize the possibility of structural damage due to differential settlement. Isolated spread footings should be extended to natural soils in the transition zone. Lateral loads due to wind or seismic forces may be resisted by friction between the foundations and the supporting compacted fill subgrade or by passive earth pressure on the foundations. For the latter, the foundations must be poured "neat" against the existing soil or backfilled with a compacted fill meeting the requirements of structural fill. A coefficient of friction of 0.35 may be used between the structural foundation concrete and the supporting subgrade. The passive resistance of undisturbed natural soils and 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). We recommend that drains be placed around all perimeter foot- ings. The drains should be constructed with a four inch diameter perforated pipe bedded and covered with free draining gravel. The drains should have a positive gradient towards suitable discharge facilities. The footing drainage system should not be tied into the roof drainage system until the drains are tightlined well away from the building. The footing excavation should be backfilled with granular soil except for the top foot which should be backfilled with a relatively impermeable soil such as silt, clay or topsoil. P.lternatively, the surface can be sealed with asphalt or concrete pavements. Earth Consultants, Inc.