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Building 1) Lc,tcr <br />ISclmunlc Ilcights Ii�siJcniial Uc��_lupmcnt <br />I;vcrctt, Washington <br />August 2R, 200G <br />CG Pilc No. ?09R <br />Pagc 2 <br />with a hcight of abuul 5 �cct �+�as locatcd abnvc Ihc ncar vcrucal c;:cavation, approxima�cly 3 tecl <br />from thc nortliwcst and southwcst comcrs of thc sidc of thc cxcavation. <br />l�hc soils cxposcd in Ihc cxcavation consistcd of densc to vcry densc, gray silty sand with gravcl, <br />intcrpretcd as glacial till. "?�hc contraclor had conswcted forms for thc foundation of I3uilding U. <br />The fi�rms wcrc ahout 3 to 5 fcct Gom the sidcs of thc excavation. You havc infurmeJ us thal thc <br />nurthcrn, wr.tcm, anJ southcro sidcs of f3uilding D havc hccn JesigncJ as rctaining walls. <br />In our opinion, thc nativc soils cxposcJ in thc sidcs of thc cxcavation should not cxcrt prcssures <br />onto thc planncJ rctaining walls of Building D. Providcd on-si�c soils arc uscd as rctaining wall <br />hackfill and arc wcll-compacteJ, �vc cxpcct that typical latcral pressurcs would bc cxcrtcJ by thc <br />backGll untu thc rctaining walis. <br />1'Vc rccommcnd thal fooling Jrains hc installcd on thc outsidc of thc fixHings. 'fhc foo�im drains <br />,hould he at Ieas� 4 inches in diame�er and shoulJ consist of perli�raled or slottcd, rigid, srtwolh- <br />���allcd PV(' pipc, i���i �� n,� n�,u�,m ��r �n� fautings. "I'hc drain linc should bc surroundcd �vith <br />frro-draining pca gre��cl or coanc sand ar.d wrappcd wilh a laycr of non-wovcn lilicr fabna A <br />vcrtical Jrainagc blankct at Icast 12 inchcs thick, consis(ing of compactcd pca gravcl ur othcr <br />Ircc-Jraining granular soils, shoulJ hc placcJ against thc walls. A vcrtical drain mat, such as <br />4liradrain G000 by �tirali Inc., may hc placcd against �hc ��•alls in licu of �hc ecrtical drainagc <br />hlankci. tiuuctural liil shuulJ thcn hc placed hchind thc vcrtical drainagc blankct or drain mat to <br />b:�cklill �hc walls. "I'hc acrtical drainagc blankct or Jrain mat shoulJ M: hydraulically connectcd <br />tu thr drain Imc at thc basc o( thc «all+. tiut7i�•icnt numbcr of cicanouts at stratcgic locations <br />sLoulJ bc ins�allcd li�r perioJical cicanmg a!'thc wa!I drain linc lo prcvcnt clogginb. <br />Projcct pl:ms pnpanJ hy <'ure UcsiEn show thc rockcrics as closc as 5 fcct ta the northwcst and <br />suuth��csi comcrs uf 13uilJing D. Wc obsr.rvcd Ihat thc distancc bch�er.n thc rockcry anJ thc <br />;ilannc�� fiwndatinns appcarr.d to bc ahout as closc as 5 fcct, consistent with thc projcct plans. <br />I hr suils widcrl�•mg �hc ruckcrics arc vcry� dcntt and thc bases of thc iockcrics arc not locztcd <br />�cithin a U.ill:l�' uulmauon of thc rctaining nalis. I�or ihosc reasons, it is our opinion that <br />latrr:d scisniic latcral ioadmg t�om thc iackcrics closc to liuilding U��•ould not excrt significant <br />la�cral prr�surrs un thr rrt;�iiung ��'alls comparcJ to lalcral loads Gom thc wall backfill. <br />Cornerstone Geotechnical, Inc, <br />