4320 THOMSON AVE GEOTECHNICAL ENGINEERING REPORT Geotech Report 2023-08-10

GeoTest Services, Inc. March 17, 2022 4320 Thomson Avenue, Everett, WA Project No. 22-0285 Foundation Support Foundation support for the proposed improvements can be established via continuous or isolated spread footings founded on firm and unyielding Advance Outwash soils, or on properly compacted structural fill placed directly over firm and unyielding native 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 up to 12 inches of soil be removed from beneath the proposed building and retaining wall foundation areas. If loose conditions are observed following the initial stripping, the subgrade should be compacted to a firm and unyielding condition with a smooth -drum roller, hoe -pack, or a similar piece of construction equipment, under feasible. Once suitable bearing conditions have been confirmed, 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 Advance Outwash soils, or on compacted structural fill placed directly above these soils may be proportioned using a net allowable soil bearing pressure of 2,500 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. 6