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September 3Q 2009 <br />Projecl No. T-6366 <br />obscrved by a rcprescntative of Tcrra Associates tn verify soil conditions are as expceted and suitable for <br />supporl. <br />Perimetcr foundafions.cxposed lo Ihe weather should Uear al a minimum depth of 18 inches below final exterior <br />grndes for frost protcction. Inlcrior Couudnlions can be conswcted at aiiy conyenient deptli below ihc floor <br />slab. I'omidations bcaring on the densc to very dcnse glacial till soils oc existing densc granu)ar structura] fill <br />can be dimensioned fm a nct nllowable bcarii�e capacity of 4,000 pounds per square foot (ps�. A rnie-ihird <br />increase in Ihis bearing value can Ue usecl when considering short-terni n�nsiiory loading. Will� strucwral <br />loading as expected and ihis reconmiendcd Uearing slress applied; estimated total and differentiai building <br />seulemen� falls in the range of one incli and one-half inch respectively. The differential movement will occur <br />u�here 1Lc building tl�v�sitious from uative tilT support to the exisling compacl fill. SettlemenEshould bc of an <br />immcdiate nature occuning as Uuilding loads are npplied. <br />I�or 8csigning foundations lo resist lateral loads, a base Giction wefficieni of 0.35 c4n be.used. Passive carth <br />pressures acting on Ihe sides of the foolings can also Ue considered.. We recommend calculatin@ tl�isJateral <br />resistance using an equivaleul fluid:weighl of 300 pounds per cubic foot (pc�. \Vc recoinmend nol including <br />the upper 12 incl�es nf soil in Ihis conipulalion becnuse it cmi be affecled by wealher or disturbed by fumre <br />grading activiry. This valuc assumcs the foundalions tvill be construcled ncat against compeient soil or <br />backfilicd with suz�ctural fill, �s described in Section 4.2 of ihis reporl. Tlie values recommended include a <br />safety fnclor of 1.5. <br />4A Sir.b-on-Gcadc rloors <br />Slab-on-gradc iloors roay be supporled on subgrade composed of competenl undisturUed nativc soil and exisling <br />dcnsc granular fill or new structural fill placed above t6csc soils. Immediately below thc iloor slab, we <br />recommcnd pincing a four-inch thick capi0ary break laycr of clean; free-draining, coarse sand ot fiuc gravel <br />th�t has icss Uian three percent passing d�e No. 200 sieve. This materi�] will rcducc d�e potential for upward <br />capillmy movemem oT�valer tlirough Ihc underlying soil ond subscqucnl wetting o(the floor slab. <br />The capillary break layer will nol prevent moisture int�Usion through tlic slaU caused by tvater vapor <br />transmission. Wherc moisturc by ��apor transmission is undesiraUle, sucli as covered Iloor arcas, a common <br />praclicc is tu place a duroUle plasticlnembranc on the enpillary brcak layer and Ihen covcr dic memlirane >t�ith a <br />I�yer of clean sand or finc gravcl to protect il from dmuage dm9ng construction, and nid in unifomi curing of the <br />concrcie s1�U: It sliould bc notcd tl�at if tl�e sand or gravel layer overlying the membrnne is salurated prior to <br />pouring Ihe sl.ib, il will be ineflecti��c in assisting in unifonn curing of thc slaU, and can actually serve as a <br />wa[er supply fa• moisWre transmission througli thc slab and affecting flooc coverings: Tlrercfore, in our <br />opinion, covcring the mcmbnuc with a laycr of sand or gravcl sliould be avoided if 11oor slaU construction <br />occurs during the wet winter moniGs and the layer ennnol be eCfectivcly drained. We recommend Iloor <br />designers and contraclors refer tn the 2003 American Concrcle Institutc (ACI) Manual of Concrete Pi.�etice, <br />Part 2, 3U2.1 R-96, for fiiilher infornintion regnrding vapor barrier iusmllation below slab-on-grade (loors. <br />� <br />Pagc No. 5 � <br />� <br />