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, � Prcliminary Gcotcchniad Lcttcr <br /> Landslidc Evaluation and Rcpair <br />�I ( 4703 Glenhaven Drivc <br /> IEvcrctt. Washinglon <br /> Febniar}' I, 20U7 <br /> I NGA rilc No. 75570G <br /> Pa�c 3 <br />' immedialciy backfillcd with rock spalls to buUress thc wall of thc excavation. No morc than ten fcet of <br /> I I lI1C L`XC1Vf1U00 �arallcl to ihc foundation linc should bc opcn at onc time. <br /> ISC�P�: <br /> We originally proposcd to caplore the northwest�rn portion of tl;c slide. on the slope wes� of S1�e <br /> ( residence, with a small limited access drill rig, and the southern portion of the slide through the driveway <br /> I pavcment with a tr.:ck-mounted drill rig. Wc havc performcd elcven borings with thc smal: limi�cd- <br /> ( access drill rig and installed threc inclinometers in lhe upper portion of the landslide mainly in the area <br /> west of the residenca For our analysis, we recommended deep soil data to better understand the <br /> Iunderlying soil condi�ions, hut you rcquestcd Ih,u we not continuc with our planned soil exploration <br /> phasc of thc projcct. <br /> IQased on our undcrs�anding of thc sitc conJitions and our discussions with you and your contractor, thc <br /> scn�ices to bc proviJed by NGA arc to: <br /> ' . <br /> I I: R.:view soil :utd gcolugic maps of�hc arc,i. <br /> 2 L'xplorc thc northwestcrly portion of thc slidc subsurfacc soil and groundw:ncr <br /> conditions with cleven 7 to 20 foot decp geotechnical borings usinc a limited-access <br /> I portable drill rig. A piczometer was installed ro measure around�vater Ievels but was <br /> tiubscquently broken by around movements. Indinometer casings werc inslalled in threc <br /> borin�s to mcasurc around movcmcn�s. Thc drill ri�was subcontractcd by NGA. <br /> � 3. Mcasurc cros� scctions of thc slopcs in thc slide aroa. <br /> d. Vcrfonn gcotcchnical Iaboralory dassification and analyses on scicctcd soil samplcs <br /> ( obtained in thc esplorations, including classification, moisturc contcnt, grain sizc. and/or <br /> dircct shcar. <br /> $, Pcrforni r.umcrical slope stabiliry analyses, as nceded. <br />, I G. Provide reconmiendations for site gr;iding ;md carthwork, including permancnt and <br /> tcmporory cut slopcs and stnictural fill. <br /> � 7. Providc rccommcndations for rctaining w:dls, including dcsi�n puramctcrs. <br /> � <br /> S. Providc rccommcnd�uion� for sitc drainagc and crosion control. <br /> � <br /> I <br /> INELSON GEOTECHN/CAL ASSOC/ATES, INC. <br /> l <br /> � <br />