1020 N BROADWAY EVCC STUDENT HOUSING Geotech Report 2022-10-25

Proposal for Geotechnical Engineering Services Proposed Apartments: 1020 North Broadway, Everett,Washington September 27,2017 4.2 BUILDING FOUNDATIONS Based on the subsurface conditions encountered at the site and our understanding of the planned development, it is our opinion the proposed building may be supported on conventional spread and continuous footings. The footings should bear on the dense to very dense, undisturbed native soil underlying the site, or on properly compacted structural fill placed on undisturbed native soil. Exterior foundation elements should be placed at a minimum depth of 18 inches below fmal exterior grade. Interior spread foundations should be placed at a minimum depth of 12 inches below the top of concrete slabs. We recommend that a maximum allowable soil bearing pressure of 5,000 pounds per square foot (psf) be used for sizing foundation elements bearing on dense to very dense native soil, or on structural fill. PanGEO should be retained to determine the adequacy of footing subgrade during construction. The recommended allowable soil bearing pressure is for dead plus live loads. For allowable stress design, the recommended bearing pressure may be increased by one- third for transient loading, such as wind or seismic forces. Continuous and individual spread footings should have minimum widths of 18 and 24 inches,respectively. Footings designed and constructed in accordance with the above recommendations should experience total settlement of less than one inch and differential settlement of less than 1/2 inch. Most of the anticipated settlement should occur during construction as dead loads are applied. 4.2.1 Lateral Resistance Lateral loads on the structure may be resisted by passive earth pressure developed against the embedded portion of the foundation system and by frictional resistance between the bottom of the foundation and the supporting subgrade soils. For footings bearing on the dense to very dense silty sand, a frictional coefficient of 0.35 may be used to evaluate sliding resistance developed between the concrete and the subgrade soil. Passive soil resistance may be calculated using an equivalent fluid weight of 350 pcf, assuming foundations are backfilled with structural fill. The above values include a factor of safety of 1.5. Unless covered by pavements or slabs, the passive resistance in the upper 12 inches of soil should be neglected. 17-233 1020 North Broadway Page 6 PanGEO,Inc.