4920 24TH AVE W Geotech Report 2023-06-22

GeoTest Services, Inc. October 8, 2021 2405 Hillside Lane, Everett,WA Project No.21-0845 properly compacted structural fill placed directly over these soils. GeoTest recommends that qualified geotechnical personnel confirm that suitable bearing conditions have been reached prior to placement of structural fill or foundation formwork. To provide proper support, GeoTest recommends that existing topsoil, existing fill (if present), and/or loose upper portions of the native soil be removed from beneath the building foundation areas. Dense, native soils are unlikely to require much preparation. However, if footings or structural fill will be placed atop previously placed fill or native Transitional Beds at depth, the surface should be compacted to a firm and unyielding condition with a smooth-drum roller, hoe- pack, or a similar piece of construction equipment. Once suitable bearing conditions have been confirmed,then foundations can bear directly on native soils or on properly compacted structural fill as described in the Fill and Compaction section of this report. Continuous and isolated spread footings should be founded 18 inches, minimum, below the lowest adjacent final grade for freeze/thaw protection. The footings should be sized in accordance with the structural engineer's prescribed design criteria and seismic considerations. Allowable Bearing Capacity Assuming the above foundation support criteria are satisfied, continuous or isolated spread footings founded directly on remedially compacted,firm and unyielding, native Transitional Beds or on compacted structural fill placed directly above these soils may be proportioned using a net allowable soil bearing pressure of 2,000 pounds per square foot(psf). The 'net allowable bearing pressure' refers to the pressure that can be imposed on the soil at foundation level. This pressure includes all dead loads, live loads,the weight of the footing, and any backfill placed above the footing. The net allowable bearing pressure may be increased by one-third for transient wind or seismic loads. Foundation Settlement Settlement of shallow foundations depends on foundation size and bearing pressure, as well as the strength and compressibility characteristics of the underlying soil. If construction is accomplished as recommended and at the maximum allowable soil bearing pressure, GeoTest estimates the total settlement of building foundations to be less than one inch. Differential settlement between two adjacent load-bearing components supported on competent soil is estimated to be less than one half the total settlement. Floor Support Floor slabs for the proposed construction can be supported on remedially compacted, firm and unyielding, native subgrade (Transitional Beds), or on properly placed and compacted structural 12