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• <br /> GeoTest Services, Inc. Report Date 7/17/2019 <br /> Anderson Residence-Everett,Washington GTS Project No.19-0384 <br /> placement of structural elements. We recommend that GTS be contracted to <br /> observe the foundation excavation prior to placement of new fill or footing formwork <br /> to verify that suitable bearing conditions have been achieved. <br /> Localized overexcavation, if necessary, can be backfilled to the design footing <br /> elevation with lean concrete,or foundations may be extended to bear on undisturbed <br /> native soil. In areas requiring overexcavation to competent native soil,the limits of the <br /> overexcavation should extend laterally beyond the edge of each side of the footing a <br /> distance equal to the depth of the excavation below the base of the footing. If lean <br /> concrete is used to backfill the overexcavation, the limits of the overexcavation need <br /> only extend a nominal distance beyond the width of the footing. In addition, GTS <br /> recommends that foundation elements for the proposed structure(s) bear entirely on <br /> similar soil conditions to help prevent differential settlement from occurring. <br /> Continuous and isolated spread footings should be founded 18 inches, minimum, <br /> below the lowest adjacent final grade for freeze/thaw protection.The footings should <br /> be sized in accordance with the structural engineer's prescribed design criteria and <br /> seismic considerations. <br /> Allowable Bearing Capacity <br /> Assuming the above foundation support criteria are satisfied, footings may be <br /> proportioned using a net allowable soil bearing pressure of 1,500 pounds per square <br /> foot (psf). <br /> The "net allowable bearing pressure" refers to the pressure that can be imposed on <br /> the soil at foundation level.This pressure includes all dead loads, live loads,the weight <br /> of the footing, and any backfill placed above the footing. The net allowable bearing <br /> pressure may be increased by one-third for transient wind or seismic loads. <br /> Foundation Settlement <br /> Settlement of shallow foundations depends on foundation size and bearing pressure, <br /> as well as the strength and compressibility characteristics of the underlying soil. If <br /> construction is accomplished as recommended and at the maximum allowable soil <br /> bearing pressure, GTS estimates the total settlement of building foundations to be <br /> less than one inch. Differential settlement between two adjacent load-bearing <br /> components supported on competent soil is estimated to be less than one half the <br /> total settlement. <br /> 10 <br />