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� Vrcliminary Gcotechnical Lcucr <br /> Landslide Evaluation :md Rep�iir <br /> I 4703 Glcnhavcn Drivc <br /> Evcrcu, Washington <br /> Fcbmary I, 2U07 <br /> � NGA Pilc No. 75570G <br /> Pagc 10 <br /> Addition:tl e�penses could include the necd for implementing addition,�l erosion control and tcmpor;�ry <br /> Idrainage measures to protcct thc slopc. <br /> ISlope Improvements <br /> We recommend that c�r.�vation hclow thc residencc hc performed in small xta;es by removing all of ;I�� <br /> soR soil from small sections of ihe slope anJ immediately backfilling euch section with rock spalls t„ <br /> bWtress the wall of thc c�cavation. No more than ten fcct of thc cxcavation parallcl to thc foundaiion <br /> line should be excavatcd at onc time. In thc area below weslcrn wall of thc residcnce, wc recommcnd <br /> that the upper wall of the excavation be immedia�ely buttressed by back(illing each small section of thc <br /> Iexcavation with rock spalls before Ihe next section of loose soil is removed. <br /> I Thc rock sp.dl slope sliould be constnicted on Ievel benches csca��ated in medium dense/stiff or beuer <br /> nativc soil. Thc levcl benches in ihc nativc soil should bc at Ic.ist four fcct wide. The maximum risc <br /> � bctwccn thc bcnchcs should bc ibur fcc�. Thc rock fill slopc should bc constructed widi a final <br /> inclination no stceper than 2 Florironlal to I Vertical (2I-I:I V). \Vc recommend that the rock slopc bc <br /> I constn�cted with 4 to 3-inch rock spalls. The rock spall fill can be tamped with the �rackhoe bucket and <br /> track rollcd into placc and �vill not rcquirc vibratory comp:�ction. Vibr:uory compaction i: not <br /> recommcndcd for use during the slopc rcp;iir. <br /> INe also recommend tliat the slope Jrainage be improved by installing drains in the new fill slope to <br /> Icolle�i grou�ldwater seepagc. The collected ��•ater should be directed through a ti�hdine pipe down the <br /> west-facing slopc and into �he existing storm drain in Glcnhavcn Dri��e. A tempomry system has becn <br /> Iconstn�cted to direct roof�vnoff through a tighUine directed down thc east-facing slope. �Ve roconuncnd <br /> lhat a permanent system to tighdine thc roof runoff �o an nppropriate ouUct be constructed during thc <br /> I Planned repairs. The roof drain system shoulJ not be connected to the subsurf:�ce drainage system. <br /> All grading operations and drainage improvements planncd as part of this project should be implementcd <br /> in a manner that enhances thc stability of the stecp slope, and docs not rcduce slope stability. r�ny <br /> cxcav:uion spoils gcnerated during site improvements shotdd not be stockpiled ncar thc slope or be <br /> allowed to encroach on the slope. \1'e anticipate that the soft soils will need ro bc removed from the site <br /> NELSON GEOTECHNICAL ASSOC/ATES, INC. <br /> 1( <br />