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Geotechnical Engineering Evaluation lierracon <br /> Broadway& 10th Starbucks Everett, WA <br /> January 9, 2014 Terracon Project No. 81135080 <br /> recommendations for subgrade improvements or an alternative foundation system may be <br /> necessary. <br /> Footing Depths and Widths: For frost and erosion protection, the bottoms of all exterior <br /> footings should bear at least 18 inches below adjacent outside grades, whereas the bottoms of <br /> interior footings need bear only 12 inches below the surrounding slab level. To reduce post- <br /> construction settlements, continuous (wall) and isolated (column) footings should be at least 18 <br /> and 24 inches wide, respectively. <br /> Bearing Provisions: Because of the unpredictable support characteristics of fill soils, we <br /> recommend complete removal of all existing fill soils below building footings. After removal of <br /> fill, footings may bear on at least medium dense native till soils or structural fill placed and <br /> compacted per the recommendations provided in this report. <br /> Bearing Capacities: Based on the bearing provisions described above, we recommend that all <br /> footings be designed for the following maximum allowable soil bearing capacities. These values <br /> incorporate static and transient (wind or seismic) safety factors of at least 3.0 and 1.5, <br /> respectively. <br /> Design Parameter Native Glacial Till Structural Fill <br /> Static Bearing Pressure 5000 psf 3,000 psf <br /> Seismic Bearing Pressure 5000 psf 3,000 psf <br /> Footing Settlements: We estimate that total post-construction settlements of properly <br /> designed footings bearing on properly prepared subgrades as recommended above will not <br /> exceed 1 inch. Differential settlements between new foundation elements over horizontal spans <br /> on the order of 50 feet could approach 1/2 inch. In all cases, these settlements would be <br /> reduced if the actual design bearing pressures are lower than our recommended maximum <br /> allowable pressures. <br /> Footing and Stemwall Backfill: To provide erosion protection and lateral load resistance, we <br /> recommend that all footing excavations be backfilled on both sides of the footings and <br /> stemwalls after the concrete has cured. Either imported or on-site granular soils can be used <br /> for this purpose. All footing and stemwall backfill soil should be compacted to a uniform density <br /> of at least 90 percent (based on ASTM: D-1557). <br /> Lateral Resistance: Footings and stemwalls that have been properly backfilled as described <br /> above will resist lateral movements by means of both passive earth pressure and base friction. <br /> We recommend using the following allowable values, which incorporate static and transient <br /> (wind or seismic) safety factors of at least 1.5 and 1.1, respectively. Allowable base friction, <br /> Reliable _ Responsive 4 Convenient _ Innovative 8 <br />