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� <br /> Robert Kincaid <br /> Junc 27, 2007 <br /> Page 5 <br /> increasingly more sensitive to small ch.mgcs in moisture content and adequate compaction <br /> becomes more difficult to achieve. Structural fill should contain no morc than about <br /> 5 percent fines for placement in wet weathec The pereent fines can be higher for placement <br /> in dry weathcr, providing that the fill material is moisturo-conditioned as necessary for <br /> proper compaction. <br /> Thc native soils and somc of the existing fill matcrial within the site consist of sand with <br /> some silt. This matcrial inay be used for structural fill provided that organic material can be <br /> isolatcd and removcd during excavation and that the soil can be moisturc-conditioncd and <br /> compacted to thc dcgrcc recommcnded bclow. <br /> Structural fiil placed in building or pavement arcas should be compacted to at Icast <br /> 95 percent of the maximum dry density determined in accurdance with ASTM D-1557. <br /> Utiliry tr�nch backfill should be compacted to at lcast 90 percent,except for the upper 2 fcet <br /> which shou(d bc compactcd to 95 percenL Wc rccommcnd that struc[ural fill be placcd in <br /> loose laycrs not more than 8 inches thick, conditioncd to the proper moisture content for <br /> compaction, and tmiformly compacted to the specified degrce before pl.�cing subsequent <br /> layers. <br /> FOUNDATION SUPPORT <br /> The proposcd residence can be supported on conventional spread and strip footings <br /> founded on tlic medium dcnsc to densc nativc soils. Wc recommend a mininumi width of <br /> 16 inches forcontinuous spread footin�s and 24 inches for isolated spread footings,pro��ided <br /> that thc allowablc bearing valuc is not e�cecdcd. Footings must bcar on mcdium dense to <br /> dcnse nativc soils. The tninimum depth of embedmcnt below final adjaccnt gradcs should <br /> be I S incl�es for exterior footings and 12 inchcs Por interior footings. Footing dcpths should <br /> also be sufficient to provide a horizontal scparation of 25 Feet benveen thc base of thc footing <br /> and the facc of the adj�cent slopc aftcr the rcgrading dcscribed in lhe CRITICAL ARGAS <br /> section of this rcport. <br /> Becausc local arcas of loose soil may Ue encountered at thc samc levcl as the medium <br /> dense to dcnse soils,we recomniend compaction of the soils beneath the footings usina hand <br /> operatcdvibratorycquipment. Anylooscordisturbedsoilsinthefootingexcavationsshould <br /> bc rccompacted prior to concretc placetnent. Pootings bcaring ou the tnedittm dense to dcnsc <br /> native soil may bc proportioned usin�an allowablc bcaring value of 2000 pounds per squcuc <br /> fooL These valucs apply lo the tot:il of dcad plus long tenn livc loads and may bc incrcased <br /> by one-third when considering design loads of short duration such as wind or seismic forces. <br /> 5��� <br /> 7505 West Lake Samincmish Parkway Northeast Redmond,Washington 98052 425-882-4850 www.tubbs.com <br />