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Everett General Hospital & Medical Center W-5557 <br /> 29 March 1983 Page 5 <br /> subsequently in this report. The base of footing excavations should be protected <br /> by a lean concrete mud slab, if construction is to be accomplished during wet <br /> weather or wet site conditions. <br /> 4.2 Foundations <br /> Continuous and individual spread footing foundations can proviae suitable support <br /> for the medical office building and parking garage structures. All footings should <br /> ext3nd to undisturbed, very dense native soils. Figure 1 of this report indicates <br /> the upper elevation of very dense native soils considered suitable for foundation <br /> support at each exploration location. If the footing excavations do not encounter <br /> l the recommended bearing soils at the initially planned depths, the footing <br /> excavations should be extended further to expose suitable soil and backfilled with <br /> lean concrete. <br /> The onsite soils are readily subject to disturbance from construction or foot <br /> traffic when damp or wet. If construction is to be accomplished during wet weather, <br /> or if surface or ground water runoff enters the excavation, it would be necessary <br /> to protect the footing subgrade soils from disturbance prior to concrete placement. <br /> Footing subgrades should be protected by placement of a thin, lean concrete "mud <br /> I slab" immediately following excavation of the footing and clean out of any loosened <br /> or disturbed soils, if construction is accomplished during wet conditions. <br /> For footings penetrating to trig prescribed bearing soils, we recommend utilizing <br /> a maximum allowable soil bearing pressure for design of any footings 3 feet or <br /> greater in width of 12,000 psf (pounds per square foot). Footings less than 3 feet <br /> wide bearing on the very dense glacial till should be designed with a maximum <br /> lallowable soil bearing pressure of 8000 psf. These bearing pressures could be <br /> increased by up to one-third to resist transient dynamic loads such as wind or <br /> seismic forces. Continuous footings should have a minimum width of 18 inches and <br /> :solated spread footings a minimum width of 24 inches. We recommend the base of <br /> I all spread footings be located a minimum depth of 1-1/2 feet below the top of floor <br /> slab or adjacent exterior grade, whichever is lower. We recommend that all footing <br /> 1 <br />