4703 GLENHAVEN DR 2016-01-01 MF Import

IYrcliminary Gcotechnir.d Letter Landslide Evaluation and Repair I 4703 Glcnhavcn Drivc Evcrett, Washington February I, 2007 ( NGA Filc No. 75570G Parc 7 I SENSITIVE AREA EVAI,UATION Seisntic Hazard I Wc revicwed the 2003 International i3uilding Codc (Ik3C) for scismic sitc classification for this project. Since stiff to hard silt and clay deposits were encountercd underlyin, the loose slide materinl on the site, Ithc u��crall sitc canditions best fit thc IBC dcscription for Sitc Class D. Hazards associated wiU� scismic activity includc liqucfaction potcntial and amplifir.uion nf ground Imotioii by soft ueposits. Liqucfactian is caused by a risc in pore pressures in a lousc, fine sand depo,it benea�h the groundwatcr lable. Thc stiff to hard silt intcrpreted to underlic the sitc has a lo�v potential Ifor liquefaction or amplification o(ground motion. IThe stiff to hard silt soils interpreted ro form the core of the sitc slope are considered stable with respect to deep-scatcd slopc failures. However, the overlying soti surficini materials on the slopcs have thc � potcntial for sloughing f:iilures during scismic cvcnts. ICrosion Hazard The erosion hazard criteri:i used for detcrmination of affected arc;�s indudes soil type, slope gradient, f vegetation covcr, and groundwatcr conditions. The erosion sensitivity is rel:ued to vegetativc cover and I the specific surface soil typcs, which are relaicd to the undcrlying gcologic soil units. The Soil Survcv of ISnohomish Countv Arca, �Vashineton, by the Soil Conscrvation Scrvice (SCS) was reviewed to dctermine thc crosion hazard of the on-sitc soils. The site surfacc soils werc classified using thc SCS � classification system as Aldenvood-Urban land comple�. S to IS percent slopes. This unit is listed as h:n�ing a slight crosion h:�zard fcr .ircas whcrc thc soils arc c�posed. It is our opinion that thc crosion � h:¢ard for thc soft soil on thc stecp slopc should hc high. I NELSON GEOTECHN/CAL ASSOC/ATES, INC. � �