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� . <br /> �'i.'J <br /> \�:`; f `�' <br /> _ ,;,i�'-`�'�.'c'\, <br /> --- - . . .. .. . ...__— . _ `. .. . . <br /> � , ' � ° t'�1C1I�' f(.; '!'I;�i'f�INf : Lr113ORA'I'ORI I;S ^ - � ^ � <br /> - � , <br /> eorvw�nnrenr:iN�Fns ' exe[uTweoFv�c[s � cor�;u�nr�rcr.rn.o,nsrs <br /> ce r.�[ sr. E[ v.o.eoxowil5 GEOLO(:ICnI s��rt��cv; <br /> STRUC7U�hLIHSTRUb1fN1nT19N - �.�TINAVENIJE\4EST S��LT[STUOnir�(;5 • <br /> YDT •ISOIP�C GltnV ULf Itn50NlC SOIL InECHnI��CS <br /> STRENCTN OF IdMERIALS LF10 SE4TTLE,WA.M119 APf'LIE�EARTII Srif.11CCS <br /> PNONE IM511HZ�� . <br /> i July 31 , 197C <br /> ' Certificate tlo. 7805-301 <br /> ; � <br /> � <br /> Seattle First �Jational Bank <br /> � � . 821 5econd Avenu? <br /> , Seattle, WA 9II104 <br /> Attention: Itr. Harry Stitle, P. E. <br /> i t•tanager, Constructidn Section <br /> • Subject: Sea-First tJational Qank <br /> � Everett h!all Qranch <br /> 1 Everett, Washington <br /> � <br /> Gentlemen: <br /> .� <br /> Our report of June 19, 1978 indicated that the site should be proof <br /> � rolled. Proof rolling serves a two-fold objective. First; to compact <br /> the soil and second, to disclose local areas that may produce differ- <br /> " ential settlement subsequent to construction of the building. <br /> 1 <br /> � <br /> The degree of compaction or density of t:�e soil is a measurable property. <br /> : Instability or pumping occurs when the compactive effort is capable of <br /> reducing the porosity of the soil but is prevented from doin9 so by the <br /> = moisture content and the permeability of the soil . The resultant lateral <br /> � <br /> ' and sometimes vertical displacement of tlie soil around the per�meter of <br /> = the compaction equipment is visibly apparent. <br /> t <br /> Corrective action to be taken when and if this unstable situation de- <br /> � <br /> , velops , is to replace the loa�er permeability soils that restrict the <br /> � escape of surplus pore �vater, �vith clean, granular soils of higii perme- <br /> '� ability. In other words, the clean, granular material should have ver•y <br /> � <br /> . little if any material passin9 tlie PJo. 40 s�ieve. There should be continu- <br /> � � ity of this clean soil such that war.er rising to or near to the surface, <br /> r <br /> i can disperse latei•ally rather than being confined in a local area. <br /> i <br /> s . <br /> �' _ <br />