3505 SHORE AVE 2016-01-01 MF Import

Geotechnical Enginecring Lettcr 3505 Shoro Avenue Dxk Addition Everett,Washiaglon May 26,2010 NGA File No.827110 Page 9 Deck Foundations Conventional shallow spiead foundetions tor the deck addidan strould be placed on undistucbed medium dense or better native soils. 'Ihese soils were rncountered approximetely 2A to 4.0 fat below ground surface in our explorations. Where undocumcntcd fill or less dease soils are cncounuccd a[the planned footi�g elevation, the subgade should be over-cxcavated to expose suitable bearing soil. 'il�e over- excavation may bc filled with swctural fill, or the footing may bo extended down to the beazing na6ve soils. If footings aro supported on swctural fill, the fill zone should extend outside the edges af the footing a distance equel to one-tialf of the depth of the ovcr-excaveNon below the bottom of the footing. The dcck footings should extend at least 18 inches below t6e adjacent finished ground surface for frost protccdon and bearing capacity consideraGons. Foundalions should be designcd in accordance with lhe 2006 Tntemational Building Code (1BC). Footing widths should be based on the anticipated loads and �Ilowable soil bearing presswe. \Water should not be allowed to accumulate in footi¢g trenchea. All loose or disturbed soil should be removed from the footing excavatior prior to placing concrete. For foundations consWcted as outlincd ebove, we rocommend an ellowable design bearing pcsssure of not more thxn 2,000 pounds per square foot (ps�be used for the de;igo of foundations suppoRed on tLo medium dense or better native soils or stnictural fi11 extending to the competent nebve soils. A representative of NGA should evaluate the foundaHon bearing soil. We should be consulted if higher be`ring pressures are needed. Cumnt IBC guidelines should be used when considering increased allowable bearing pressure for short-term transitory wind or seismic loeds. Potential foundation settlement using the recommended nllowable beaiing pressu�c is estimaled to be less than one-inch total mid %:-inch differentia! between adjacent footings or across a distance of about 30 fcet based on our experience with similar projects. Lateral loads may be resisted by fi-iction on tbe base of the tooting and passive resistance against the subsurface pofions of the foundaHon. A coe8�icient of friction of 0.35 may be used to calculate the bau friction end should be applied to tk�e verticel dead load only. Passive resistsnce may be calculated as a Uiangular equivalent Eluid presswe distribution. An equivalent fluid density of 200 pounds per cubic foot (pc�should be used for passive resistance design for a level ground surface adjacent to the foodng. T6is level surface should extend a distance equal to et least three times tho footing depW. 'Ihese recommended NELSON GEOTECHNICAL ASSOCIATES, INC. /�/�j