1910 MERRILL CREEK PKY 2018-11-15

Intracorp E-3592-520 - September 23, 1998 Page 6 For frost protection, exterior foundations elements should be placed at a minimum depth of eighteen (18) inches below final exterior grade. Interior spread footings can be placed at a minimum depth of twelve (12) inches below the top of slab, except in unheated areas, where interior foundation elements should be founded at a minimum depth of eighteen (18) inches. Continuous and individual spread footings should have minimum widths of eighteen (18) and twenty-four (24) inches, respectively. With foundation support obtained as described, footings may be designed for an allowable soil bearing capacity of three thousand (3,000) psf for competent native soil or structural fill. Loading of this magnitude would be provided with a theoretical factor-of-safety in excess of three against actual shear failure. For short-term dynamic loading conditions, a one-third increase in the above allowable bearing capacities can be used. Horizontal loads can be resisted by friction between the base of the foundation and the supporting soil and by passive soil pressure acting on the face of the buried portion of the foundation. For the latter, the foundation must be poured "neat" against competent native soils or backfilled with structural fill. For frictional capacity, a coefficient of .35 can be used. For passive earth pressure, the available resistance can be computed using an equivalent fluid pressure of three hundred fifty (350) pcf. These lateral resistance values are allowable values, a factor-of-safety of 1.5 has been included. As movement of the foundation element is required to mobilize full passive resistance, the passive resistance should be neglected if such movement is not acceptable. Footing excavations should be observed by a representative of ECI, prior to placing forms or rebar, to verify conditions are as anticipated in this report. Slab-on-Grade Floors Slab-on-grade floors may be supported on competent native soils or on structural fill used to modify site grades. Where loose soil is encountered at the slab subgrade elevation, the loose soil should be compacted to the previously discussed requirements for structural fill. Disturbed subgrade soils should either be recompacted or replaced with structural fill. Concrete slabs should be provided with a minimum of four inches of free-draining sand or gravel. In areas where slab moisture is undesirable, a vapor barrier such as a 6-mil plastic membrane may be placed beneath the slab. Two inches of damp sand may be placed over the membrane for protection during construction and to aid in curing of the concrete. Seismic Design Considerations The Puget Lowland is classified as a Seismic Zone 3 in the 1997 Uniform Building Code IUBC1. Earthquakes occur in the Puget Lowland with regularity, however, the majority of these events are of such low magnitude they are not detected without instruments. Large earthquakes do occur, as indicated by the 1949, 7.1 magnitude earthquake in the Olympia area and the 1965, 6.5 magnitude earthquake in the Midway area. Earth Cansuhante, I�c.