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i <br /> ' Wc rcrnmmcnd a basc coursc laycr bc placcd bclow ncw pavcmcnts, slabs-on-gradc, and thc base of <br /> subsurfacc fn.,ilitics or ncw vaults. Dcneuth new slab-on-grade or vnults, lhe base coursc should consist <br /> of a minimum 6•inch-thick laycr of '/.•mch minus cican crushcd gravcl with ncgligiblc sand or silt, to <br /> proaidc unifortn supporl anJ to function ns a capillary brcak. Wc rccommend the base course beneath <br /> ncw asphah p�vemcnt consist of crushed surfacing basc cour.ce in accordancc with WSUOT Spccification <br /> i 9-03A(3)tiwth the exccption that the fincs contcr.t be limited tn 5 perccnt. Additional dclails nrc provided <br /> in thc"Slahs-cm-Grad�'nnd"Pavcmcnt Considcrations" scctions of this rcport. <br /> ( Structural Flll Placement <br /> Swciural fill should be placcd in horizoNal lilis, which are 10 inches or Icss in loose thickness. The <br /> I moisturc comcnt of thc fill soil musl bc adjusted as nccessary to achicv.: the rcquircd dcgrce of <br /> compaction. Gach lill musl be compacted to thc appropriatc specitication before placing subscqucnt <br /> laycrs. Bach lifl should bc uniformly compacicd to at least 95 perccnt of thc maximum dry dcnsiry <br /> I (MDD) as dctcnnincJ in accordancc with Ihc AST'M D-1557 tcst method bcncath ncw slabs, <br /> foundalions, and within 2 fcct of thc finished subgradc surfacc for pavcmcnt arcas. 7'hc compaction <br /> critcria cnn lx rcduccd to 90 perccnt oithc MDD for fill placcd mnrc thrn 2 fcct bclow thc pavemcnt <br /> subgradc surfacc. <br /> IWc recommend that a gcotcchnical enginecr ohserve Ihe preparation t��r, placcment, und compaction of <br /> slruclural till. An adcquatc numhcr of in-placc Jcnsity icsts should bc perfortncd in thc fill lo cvaluatc if <br /> I thc specified dcgrec of compaction is bcing achic�ed. The frcquency of testing will he dependent on the <br /> construction progress, moisiurc contcM of soils and difiiculry of nchicving compaction, lift thickncss and <br /> compaction mcU�nds. <br /> i <br /> � Use o/Exlsting Slte Solls <br /> i l'hc rcsults of our laboratory tcsis indicatc thc surlicial fill soils bcncath thc existing pavcmcnt arc ncar <br /> thc uptimum moisturc cnntcm rcyuircd for compaction. Ilowcvcr thc silty sand fill soil cncountcrcd in <br /> ihc tcst pits is significanNy nhove optimum maisture cnntcnt and will require cxtendcd dry wca�her and <br /> moisturc conditinning hcforc it will bc suitahic 1'or usc as stnictural fill. All soils encountcrcd at Ihc sitc <br /> , arc moisturc-sensitivc nnd should only bc rcuscd for siructural fill during dry wcathcr conditions. <br /> SLABS-ON•GRADE <br /> Wc rccomrocnd a 6-inch-thick I:iycr of ;5-�nch minus cican crushcd gravcl µ�ith ncgligiblc sand or sill <br /> undcrlic ncw slnh-on-gradc to providc unifortn supporl and lo function as a capillary brcak. All loosc <br /> I soils should Ix rcmovcJ from thc cxcavation and thc subgradc should bc compacicd and cvaluated by thc <br /> gcotcchnical cnginccr pnnr ia placing thc rccommcndcJ subbasc. Wc rccommcnd a subgradc modulus of <br /> I50 pounds per cubic inch for Ihe slab suppnrted on thc recommended subbase overlying existing fill <br /> Isoiis prcparcd as rccommcndcd abovc. <br /> SHALLOW FOUNDATION SUPPORT <br /> Wc rccommcnd an allowablc soil bcaring pressurc of 3,000 psf bc utilizcd for design of footings <br /> aMicipaled to he faunded within �he up�r 2 feet of sitc grade on cxisting dense fill. This vulue can Fc <br /> incrcascd lo R,000 psl'whcrc footings arc ti�undcd on vcry dcnsc glacial till. Wc rccommcnd thc cxposcd <br /> ! suhE�radc bc compacted fi�llowing cxcava�ion. Footing subgradc should hc cvaluatcd by a rcprcscmativc <br /> from our linn to conlimi canditions arc as assumed during dcsign. <br /> I <br /> I Filr n'o.:uv!-nly�2t --- Page 6 G[OENGINEEII� <br /> � 1hn� ,• 'uiw <br />