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i&***6k <br />MR ENGINEERING <br />Footing Subgrade Allowable Bearing <br />Capacity <br />Static <br />Compacted Structural Fill over 2,500 psf <br />Undisturbed Vashon Till deposits <br />Undisturbed Vashon Till deposits 3,000 psf <br />These static bearing pressures can be increased by one-third when used with alternative basic load <br />combinations that include wind or earthquake loads. This recommendation is in accordance with the <br />International Building Code (IBC) 2015, Section 1806. <br />Subgrade Verification <br />All footing subgrades should consist of firm, unyielding, non -organic, native soils or compacted structural <br />fill materials. Under no circumstances should footings be cast atop loose, soft, or frozen soil, slough, <br />debris, existing uncontrolled fill, or surfaces covered by standing water. We recommend that the <br />condition of all subgrades be verified by a MPE geotechnical engineer before any fill or concrete is placed. <br />Footing Settlements. <br />We estimate that the total post -construction settlement of properly sized footings bearing on properly <br />prepared subgrades will not exceed 1 inch. Differential settlements may approach one-half of the total <br />settlement over horizontal distances on the order of 50 feet. <br />4.6 SLAB -ON -GRADE FLOORS <br />In our opinion, if subgrades are prepared as described in the Site Preparation section of this report, a <br />soil -supported slab -on -grade floor may be used for the proposed structures. We offer the following <br />comments and recommendations concerning slab -on -grade floors. <br />Subgrade Conditions and Verification <br />All soil -supported slab -on -grade floors should bear on firm, unyielding native soils or on suitable <br />structural fill soils. We recommend that the condition of all subgrades and overlying layers be verified <br />by a MPE geotechnical engineer prior to any fill or concrete is placed. <br />Floor Subbase <br />Structural fill subbases do not appear to be needed under soil -supported slab -on -grade floors at the site. <br />However, the final decision regarding the need for subbases should be based on actual subgrade <br />conditions observed at the time of construction. <br />MP ENGINEERING, PLLC MPGEOTECH.COM 12 <br />