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+ Prdiminary Gcotcchnical Lcttcr <br /> Landslidc Evaluation and Repair <br /> I 4703 Glcnhaven Drivc <br /> Evcrett. Washington <br /> February I, 2007 <br /> ( NGA Filc No. 75570G <br /> Pagc 9 <br /> Thc surficial soft soils in thc arca of the sliJc repair are considcrcd extrcmcly moisture scnsitivc and arc <br /> � currcntly in a soft and s;uuratcd condition. We do not anticipatc that the surfici:�l soil in thc slidc arca <br /> will support an excava�or or othcr equipment of similar siza It m.ry be necessary ro excac:uc soft <br /> � matcrials and constnict a rock pad cxtcnding to nativc soil immediatcly as thc cxcnvation is adcanccd in <br /> order to be ablc to move thc excavator from ihc driveway to support it on the slope. <br /> IThc removal of thc soft soils will also result in a stccp c�cavation w:�ll that will cstend to thc top of thc <br /> I landslidc scarp. At thc ncarest point. thc scarp is approximaicly fivc fcet west of the westem wall of thc <br /> residence. Our explur:uions near the westem wall of the residence encountercd very stiff to hard silt soil. <br /> r However, becausc lhc large excavation will be so close to thc residence, we reconunended that 1he <br /> � foundations ncar thc cxrrvation bc undcrpinncd as a prccaution against furthcr slopc failures during <br /> � excavation. 1'ou have infarnred us that you do not plan tn underpin tlie residence foundations prior to the <br /> exc:�vation and repairs ro tlie xlope. We c:mnot accept responsibility or liability for d:miage to the <br /> � residence due to the excavation and repairs if you choose not io underpin the fotmdations. If thc <br /> residence found,itions �u'c not unJcrpinned. the escav:uion stabiliry will need to bc monitorcd closcly by <br /> thr contractor. <br /> I <br /> Erosion Cunlrol <br /> ( <br /> I Thc sitc soils can havc u high crosion potcntial. dcpending on how thc sitc is gradcd and ho��� wutcr is <br /> allowcd to conccntratc. Bcst Managenunt Pructices (BMPs) should bc uscd to control crosion. Arcas <br /> Idismrbed during constniction should be protected from crosion. Mcasures tnken may in�lude divcrting <br /> surface water :nvay from the slide and excavation are:�s. Silt fences or straw bales should be crected to <br /> �, I <br /> ; prevent nmdJy wa�er from flowing over lhe site slopes ur down to�vards Glen Haven Drive. Distur6ed <br /> arcas should be replantcd with vegetation at U�c end of construction. The vegetation should bc <br /> m.�intained until established. rinal gr:iding should incorpor:ue appropriate crosion convol measures to <br /> route stormwater�Unoff away from the top of slopes and to appropriate discharge loauions. <br /> To Icssen the p xcntial impacts oF cnnstn�ction on thc slope and to rcduce cost overruns and delays, we <br /> recommend that constniction take place during the extended periods of dry ��•eather if possible. If <br /> consu•uction takcs pl:ice durin�; Ihe ���ct weather. additional espenses and delays shoold be expected. <br /> I NELSON GEOTECHN/CAL ASSOC/ATES, INC. <br /> In <br /> � <br />