10105 19TH AVE SE Geotech Report 2018-01-02 MF Import (2)

KA No. 092-06160 October 25,2006 Page 8 Foundations The proposed addition may be supported on a shallow foundation system bcaring on thc medium dense to dense native soils or on structural fill, placed on medium dcnse to dense native soils. Footings may be designed for a net allowable bcaring pmssure of 2,500 pounds per squarc Foot(ps�, dead plus live load, for footings whicl�bear on medium dense to da�se native soils or on strucmral fill,placed on the medium dense to densc nativc soils. A 1/3 increase in thc above value may be used for short duration, wind and seismic loads. Stnictural fil( placcd on benring, nntivc subgrade sliould be compacted to at l..ast 95 percent oFthe maximum dry densily based on ASTM Tcst Mcthod D1557. All footing subgradc areas should be inspected to verify suitable material for the design bcaring pressure. We recommend that all Cooting excavations be inspected by a rcprescntative of the geotechnical cngincer to verify that thc soils arc in a suitable condition f'or the allowable design bearing pressure (for footings) prior to concrete placement. If loose and/or moisture disturbed soils are encountered in certain footing areas, recotnmendations for overexcavation and replacement 611 will be provided during the inspcetion work. �xterior footings should have a minimum dcpth of 18 inches below pad subgrade(soil grade)or adjacent exterior grade, whichevcr is lower. Poolings should have a minimum width of 12 inches regardless of load. If constructed as recommerded, thc tomi setdement is not expectcd m excecd 1 inch. Differential settlemenl, along a 20-foot exterior wall footing, or between udjoining column Cootings, should be less than %z inch, producing an m�gular distor[ion of 0.002. Most settlement is expected to occur during construction,as thc loads ate applied. Howevcr,additional post-oonsWction scttlemcnt may occur if the foundation soils are ilooded or saturated or if a strong seismic evcnt results in liquefaction of the unJerlying soils. It should be noted thatlhc risk oFliquefaction is considered low,givcn the composition and dcnsity of thc nativc,cn site soils. Seasonal rainfall, watcr run-off, and Ute normal practicc of watering trees and landscaping areas around the proposed swcturc, should not be pem�itted ro flood and/or saturate footings. To prcvcnt the buildup of water within thc Cooting arcas, continuous fooling drains (with cleanouts) should bc provided at the bases of the footings. The footing drains should consist of a minimum 4-inch diamctcr perforated pipe, sloped to drain, with perforations placed down and enveloped by 1-incL sized washed rock in all directions and f ller fabric to prevent the migration of fines. Resistance to lateral footing dispinccment can be computed using an allowable friction factor of 0.32 acting between lhe bases of foundations and the supporling subgradc. Lateral resistance for footings can alternatively be deve(oped using an allo�vable equivalent fluid pa�sive pressure of 290 pounds per cubic Coot (pc� acting against the appropriate veRical footing faces. The allowable friction factor and nllowablc cquivalent fluid passive pressurc values include tt Cactor of safety of 1.5. The frictional and passivc resistance of ttte soil may bc combined without reduction in determining the total lateral resislance. A 1/3 iucrease in the above valucs may be used For short duration,wind and seismic loads. Krazen&A�sociatee,inc. 4� Oflices Serving The Weslem United States �1 �