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Premier Storage Everett, LLC ES-2432 <br /> June 26, 2012 Page 8 <br /> Revised June 28, 2012 <br /> Foundations <br /> Based on the results of our study, the proposed storage structures can be supported on <br /> conventional spread and continuous footings bearing on competent native soils, competent <br /> existing fill soils, re-compacted native soils, or structural fill. Due to the presence of up to about <br /> seven feet of loose fill, footings for the new buildings should be overexcavated a minimum of <br /> four feet below the bottom of the footing elevation and grades restored with structural fill. <br /> ESNW should observe the overexcavation to confirm conditions and provide additional <br /> recommendations for the foundation subgrade support. Additional depths of overexcavation <br /> may be necessary depending on the soil conditions observed during construction. Where loose <br /> or unsuitable soil conditions are exposed at foundation subgrade elevations, compaction of the <br /> soils to the specifications of structural fill, or overexcavation and replacement with structural fill, <br /> may be necessary. Organic material exposed at foundation subgrade elevations must be <br /> removed and grades restored with structural fill. <br /> Provided foundations will be supported as described above, the following parameters can be <br /> used for design of new foundations: <br /> • Allowable soil bearing capacity 2,500 psf <br /> • Passive earth pressure 350 pcf (equivalent fluid) <br /> • Coefficient of friction 0.4 <br /> A one-third increase in the allowable soil bearing capacity can assumed for short-term wind and <br /> seismic loading conditions. The above passive pressure and friction values include a factor-of- <br /> safety of 1.5. With structural loading as expected, total settlement in the range of one inch and <br /> differential settlement of about one-half inch is anticipated. The majority of the settlements <br /> should occur during construction, as dead loads are applied. <br /> Seismic Design Considerations <br /> The 2009 International Building Code specifies several soil profiles that are used as a basis for <br /> seismic design of structures. Based on the soil conditions observed at the test sites, Site Class <br /> C, from table 1613.5.2, should be used for design. In our opinion, the site soils have a low <br /> susceptibility to liquefaction based primarily on the lack of shallow groundwater and the density <br /> of the underlying native soil. <br /> Earth Solutions NW, LLC <br />