1815 13TH ST SEATTLE CHILDRENS NORTH CLINIC Geotech Report 2022-10-25

Detention Vault Foundation For the foundation constructed as recommended in this report,we recommend using an allowable bearing pressure of 6 ksf bearing on the dense to very dense or hard glacially consolidated soils located below existing site grades.The allowable soil bearing pressure applies to the total of dead and long-term live loads and may be increased by up to one-third for wind or seismic loads.The allowable soil bearing pressures are net values. Settlement Provided that all loose soil is removed and that the subgrade is prepared as recommended under "Construction Considerations" below, we estimate that the total settlement of shallow foundations will be about 1 inch or less. The settlements will occur rapidly, essentially as loads are applied. Differential settlements between footings could be half of the total settlement.Note that smaller settlements will result from lower applied loads. Lateral Resistance Lateral foundation loads may be resisted by passive resistance on the sides of footings and by friction on the base of the shallow foundations. For shallow foundations supported on native soils, the allowable frictional resistance may be computed using a coefficient of friction of 0.4 applied to vertical dead-load forces. The allowable passive resistance may be computed using an equivalent fluid density of 400 pounds per cubic foot(pcf) (triangular distribution). These values are appropriate for foundation elements that are poured directly against undisturbed glacially consolidated soils or surrounded by structural fill. The above coefficient of friction and passive equivalent fluid density values incorporate a factor of safety of about 1.5. Light Pole Foundations Drilled shaft recommendations are provided in general accordance with Section 1807.3 of the 2012 IBC. We recommend that the drilled shafts supporting the light poles be a minimum of 12 inches in diameter and should have a minimum embedment depth of 6 feet. We recommend that drilled shafts be designed with an allowable lateral bearing pressure of 300 pounds per square foot per foot(psf/ft). For a shaft with a 6-foot embedment,this results in an Si value of 600 psf and an S3 value of 1,800 psf, per Section 1807.3.2 of the 2012 IBC. Deeper embedment will result in higher Si and S3 values, up to no more than twice the Si and S3 values provided. Construction Considerations If soft areas are present at the footing subgrade elevation,the soft areas should be removed and replaced with lean concrete or structural fill at the direction of GeoEngineers. All loose soil and other debris should be removed from the foundation excavations prior to placing reinforcement steel and concrete. Loose or otherwise soft soils not removed from foundation subgrade areas can result in excessive foundation settlement. GEOENGINEERS April 22,2016 Page 6 File No.'073&0;00":