10200 19TH AVE SE COSTCO FUEL STATION Geotech Report 2022-10-25

GEOTECHNICAL ENGINEERING STUDY Costco Wholesale c/o Barghausen Consulting Engineers E-8556 January 13, 1999 Page 6 For foundations bearing on at least two feet of structural fill, an allowable soil bearing capacity of two thousand five hundred (2,500) psf can be used. Footings bearing on the competent native soils underlying the fill can be designed using an allowable soil bearing capacity of five thousand (5,000) psf. Continuous and individual spread footings should have minimum widths of eighteen (18) and twenty-four (24) inches, respectively. Loading of this magnitude would be provided with theoretical factor-of-safety in excess of three against actual shear failure. A one-third increase in the above allowable soil bearing capacities can be assumed for short-term wind and seismic loading conditions. Exterior foundation elements should be placed a minimum depth of eighteen (18) inches below final exterior grade. Interior spread foundations can be placed at a minimum depth of twelve (12) inches below the top of slab, except in unheated areas, where interior foundation elements should be founded at a minimum depth of eighteen (18) inches. Assuming foundation support for the proposed structures is in accordance with the recommendations contained in this report, we expect total settlements of approximately one inch and differential settlement of approximately one-half inch. Most of the anticipated settlements should occur during construction as dead loads are applied. Lateral loads can be resisted by friction between the base of the foundation and the supporting soil, and by passive soil pressure acting on the face of the buried portion of the foundation. The foundation excavations must be backfilled with structural fill to establish adequate passive resistance around the foundation elements. Resistance to lateral loads from passive earth pressures can be calculated using an equivalent fluid pressure of three hundred fifty (350) pounds per cubic foot (pcf). For frictional capacity, a coefficient of 0.40 may be used for foundations elements bearing on competent native soils or structural fill. These lateral resistance values are allowable values, a factor-of-safety of 1 .5 has been included. Footing excavations should be observed by a representative of ECI, prior to placing forms or rebar, to verify that conditions are as anticipated in this report. Compaction testing of structural fill in foundation areas should be periodically performed by ECI. Earth Consultants, Inc.