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Geotechnical Engineering Report 9 January 7,2020 <br /> QFC 852 Fuel Station,Everett, Washington RG1 Project No.2019-258A <br /> 5.4 FOUNDATIONS <br /> As discussed above, the very loose fill encountered at the site is not suitable for <br /> supporting the canopy foundation directly. The very loose fill should be removed and <br /> replaced with structural fill. The proposed canopy foundation can be supported on <br /> conventional spread footings bearing on medium dense native soil or structural fill. <br /> Perimeter foundations exposed to weather should be at a minimum depth of 18 inches <br /> below final exterior grades. Interior foundations can be constructed at any convenient <br /> depth below the floor slab. Finished grade is defined as the lowest adjacent grade within <br /> 5 feet of the foundation for perimeter (or exterior) footings and finished floor level for <br /> interior footings. <br /> Table 4 Foundation Design <br /> Design Parameter Value <br /> Allowable Bearing Capacity— Native soil or 2,500 psf1 <br /> structural fill <br /> Friction Coefficient 0.25 <br /> Passive pressure (equivalent fluid pressure) 250 pcf2 <br /> Minimum foundation dimensions <br /> Columns: 24 inches <br /> Walls: 16 inches <br /> 1 psf=pounds per square foot <br /> 2 pcf=pounds per cubic foot <br /> The allowable foundation bearing pressures apply to dead loads plus design live load <br /> conditions. For short-term loads, such as wind and seismic, a 1/3 increase in this <br /> allowable capacity may be used. At perimeter locations, RGI recommends not including <br /> the upper 12 inches of soil in the computation of passive pressures because it can be <br /> affected by weather or disturbed by future grading activity. The passive pressure value <br /> assumes the foundation will be constructed neat competent against soil or backfilled with <br /> g <br /> structural fill as described in Section 5.2.4. The recommended base friction and passive <br /> resistance value includes a safety factor of about 1.5. <br /> With spread-footing foundations designed in accordance with the recommendations in <br /> this section, maximum total and differential post-construction settlements of 1 inch and <br /> 1/2 inch, respectively, should be expected. <br /> 5.5 RETAINING WALL <br /> If retaining walls are needed for a detention vault or site retaining walls, RGI recommends <br /> cast-in-place concrete walls be used. The magnitude of earth pressure development on <br /> retaining walls will partly depend on the quality of the wall backfill. RGI recommends <br /> placing and compacting wall backfill as structural fill. Wall drainage will be needed behind <br /> 1.1 <br /> 11- <br /> RILEYGROUF <br />