1315 MADRONA AVE 2016-01-01 MF Import

�eotechnical Engineenng P.epart 1313 Madrona Avenue Everett, Washington March i l, 2013 RN File No. 2793-001 A Page 7 Foundations Conven[ional shallow spread foundations should be fourded on undisturbed, medium dense or firmer soiL If the suil at the planned bottom or footmg elevation is not suitable, it should be overexcavated to expose surtable bearing soil. Footings should extend at least 18 inches belo� the towest adjacent finished ground surface for frost protecUon. Nlinimum foundation widths should coniorm to IBC requirements. Standing v✓ater should not be allowed to accumulate in !ooting trenches. All loose or disturbed soil should be removed irom the f�undation excavation prior to plaang concrete. For foundations constructed as out6ned above, we recommend an allowable design bearing pressure of 2,500 pounds per square foot (psf� be used for the iooting design. IBC guidelines should be followed when considering short-term transitury :vind or seismic loads. Potenval foundation settlement using the recommended allowable bearing pressure is estimated to be less than 1-inch total and 'fi-inch differential between footings or across a distance of about 30 (eet. Higher soil bearing values may be appropriate with wider fooungs. These higher vaiues can be determine�+ after a review of a specific design. Lateral Loads The lateral earth pressure acting on retaining walis is dependent on the nature and density of the soil behind the wall, the amount of lateral wall movement, which can ocr,��r as backfill is placed, and tne inclination of ihe backfill. Walls that are free to yield at least one-thousandth of Ihe height of the wall are in en "active" condition. Walls restrained from movement by sUffness or bracing are in an "at-rest" condition. Active earth pressure and a[-rest eanh pressure can be calculated based on equivalent fluid density. Equivalent flwd dens�t�es for ac[ive and at•res[ earth pressure of 35 pounds per cubic foot (pc0 and 55 pcf, respectively, may be used for design for a level backslope. These values assume that the on-sde soils or imported granular fill are used for backfill, and that the wall bac4;fill is drained. The preceding values do not include the effects of surcharges, such as due to foundation loads or other surface loads. Surcharge e(fects should oe considered where appropriate The above drained acUve and at-rest values should be increased by a uniform pressure of 6.3H and 19JH psf, respectively, when considering seismic conditions using 2009 IBC. The above drained acuvc. and at-rest values should be increased by a undorm pressure oi 7.4H and 22.7H psf, respectively, when considering seismic conditions using 2012 IBC. H represenis ihe wall height The above laterai pressures may be resis[ed by fnction at the base of the wall and passive resistance against the (oundation. A coe(ficient of fnction o( 0.45 may be used to determine [he base (riction in the native glacial soils An equivalent fiuid densiry of 795 pcf may be used for passive resistance design. To achieve Ihis value of passive pressure, the foundations should be poured "neat" against the nati�•e dense soils, or compacted fili should be used as backiill against the front of the footing, and the soil in front of the wall should extend a horizontal distance at least equal to three times the foundalion depth. A factor of safety of 1.5 has been applied to Ihe passive pressure and the friction coefficient to account for required movements to generate '. •:se pressures. Robinson Noble, Inc