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Itc�:iinin� ��all ('u�utructiun <br /> In ordcr to crcalc.f Icvel building �ad li�r thc �ilamnd nsidcncc. it �vill hc ncccti�;fry to c�mstru�t <br /> a retaining wall(s) across thc lower�rtion of Uic noKh and east sidcs of the pro,nerty. "f'he <br /> rctaining walls will step up and be keyed into the northcast sloping ground surfacc. Thc typc ul <br /> ��.JI currenUy under considcration is a segmental block wall witL an associated mechanically <br /> stabilizcd corth (MSG) fill. MSL-: fills are sclf-supporting duc to intemal minforccmcnt�vith <br /> horizontal I:�ycrs of g�rogrid. 7'hc embcddcd gcogrid providcs thc intcmal strcngth to support <br /> thc till and thc sc�ncntal block woll lacing pmvidc; Ihc long Icrtn crosion control i�or thc ncar <br /> vcrtical lill f:icc. "Ilie gcogrid reinforccd wall/fill wil! bc e;apaUle of providing suitablc supp��rt <br /> tirr thc planncd rosidence and will also greaUy rcduce the potential for future movement�f thc <br /> cxisting slope seJimenls. A lypical dcsign detail for the planned wall is attached t�� �his n•i,�,u <br /> Wall design calculations are also included. <br /> l�hc actual wall or walls loc:atiuns have not bccn finalized at the ume of this rc�mrt. \�'�� <br /> anticipate that one tall �vall or two smaller walls may be necessary to crcate the gra�c, nccc�sar� <br /> tu suppott ilic residence and garage fi�undations. Hecause of the significant gradc diflcrencc <br /> bctwcen thc access off of I3roadway to the low poinl of the pl.�nncd dcvclopmcnt arca, wc <br /> anticipate that multiple wall locations may be necessary to achicvc lhc reyuired level benchc:: tu <br /> support thc pl:uincd dcvclopmcnL 'I'hc currcnt wall design allows for a 3H:1 V �lopc tx�twccn <br /> the top ofa lower wall and the toc ofthe next wall or huuse foundation above. 11ic upper �ti,ill <br /> base or foundation must hc a miaimum of 10 fcct horizontal in back of thc back of thc lo���cr <br /> wall blocks:uid if a slo�x: is maintained lx;twccn lhc lowcr wall and upper swcturc, a minimum II <br /> of 3 fcct away from lhc upper structurc thc slope must (lntten (o horizontal, All sloping ground <br /> bctwccn structural clements must be pla.ced and compactcd as previously discusscd lor <br />� structural fill. Wc strongly rccommend that thc final housc, garagc and retaining wall locations <br /> an� grade catches be reviewecl by 13GC, plle onee these plans are available to verify that the <br /> surcharges:u�d wall hcights arc ccnsistent with thc prcliminary wall dcsign. It is also possiblc � <br /> that anothcr typc of rctaining wull may be choscn lo providc gradc scparation. We art: availahlc <br /> to providc spccific gcotechnical dcsign considcmtions for other typcs of rctaining wall once <br /> p:aus arc availablc. i <br /> Installation uf the MSG wall should begin by cxcavating a horizontal bearing pad for the wall � <br /> foundation and reinforc:cd fill. The foundation excavation may step vertically along its length, <br /> but it is cssential that the wnll blocks mid gcogrid reinfon;ed till be placed on horizontal pads cut <br /> into the dense, native sedimcnLs bcncath thc topsoil and wcathemd zone. The undisturbed, <br /> dense native sediments will he capable of providing the myuircd 3400 pcf hearing capacily for <br /> support of thc wall. "11ic basc row of wall block nccds t�r mainlain a minimum of 24 inches of <br /> cmtxdment at all la;ations along the watl ba.ec. 'I'hc pr�parcd subgradc should bc evaluatcd by a <br /> rcpresentative of this firtn prior to placing the basc wall blocks W vcrify suitablc foundation <br /> bcaring conditions for thc wall. <br /> Once Uie subgrade has l�een prepared and approved by the geotechnical engincer, the basc wull <br /> blocks m�y be set. 'fl�e base blocks should be set on a levcling course oP5/8 inch crushed rock. <br /> With the base blocks set, their alignment should be checked :u�d the first layer of backfill placed <br /> and compacted. 1'he fill soil placcd behind the wull shouM be mineral soil fne of organics. 'I�e <br /> backfill should bc placcd in maximum 8 inch loosc lifts and cach lift shall bc:.ompactcd to a <br /> minimum of 95 percent of Uic modificd Proctor maximum dry dcnsity per AS'1'M:D-1557. 7'hc <br /> first laycr of gcogrid roinforccment will bc placcd atop thc basc row of blocks. 'fhc Icngth of <br /> li(;t'. ��Ilc 1•I"_'b7 �09��� ,���rnuc NI?. Woodincillc. WA 9R077 (425) ?7i-SO(i2 �� <br /> �) <br /> � <br />