1515 132ND ST SE Geotech Report 2022-10-25

Proposal for Geotechnical Engineering Services Proposed Bank: 1515 132nd Street Southeast, Everett, Washington March 15, 2019 water pressure, causing the soil to behave as a fluid. Soils with a potential for liquefaction are typically cohesionless, predominately silt and sand sized, must be loose, and be below the groundwater table. The site is predominantly underlain by very dense silty sand with gravel without a defined groundwater table. Based on these conditions, in our opinion the liquefaction potential of the site is negligible and design considerations related to soil liquefaction are not necessary for this project. 5.2 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 spread footings. The footings should bear on the medium dense to very dense, undisturbed native soil underlying the site, or on properly compacted structural fill placed on undisturbed native soil. We encountered 3 to 4'/2 feet of fill below the site. If fill is encountered at the foundation subgrade elevation, the fill should be overexcavated and replaced with properly compacted structural fill. The overexcavation width should extend at least one foot beyond the width of the foundation elements. Exterior foundation elements should be placed at a minimum depth of 18 inches below final 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 2,500 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. 19-049 1515 132nd St SE Page 6 PanGEO, Inc.