4805 BELVEDERE AVE 2016-01-01 MF Import

Subsurfare Ezplormion, Geologic Na:ard, and Hel�eAr�e Lots c'�ut Preliminary Geofeehnical Engineenng Report F�rrerr Washingron __ Geologic Hamrdr nrut Mitigaions 5.4 Ground Dlotion It is our opinion that any earthquake damage ro the proposed structures when founded on suitable bearing strata in accordance with the recommendations contained herein will be caused by the intensity and acceleration associated with the event and not any of the above-discussed impacts. Structural design of the building should follow ]997 Unijorm Building Ccde standards for Seismic Zone 3(Z factor=0.3) and an So soil type. G.0 LANDSLIDE IIAZARDS AND MITIGATfONS As previously discussed, the proposed building locations are� ear the to of th�e st� slope that forms the west Oank of the drainagc ravine. prept re percq _ . Vegetation throughout the steep slope consists of extremely thick natural brush with scattere� deciduous vees. Because of the thicA brush, our reconnaissance of the slope was limited to three surveyor's trails cut through the brush down to the creek at the bottom of the ravine behind Lots 32 and 33. We were also able to access the uaper and middle portions of the slope on the adjacent property to the south because the underbrush was not yuite as thick in this area as elsewhere on the slope. During our reconnaissance, w slol�"�PP�at�;'tb%b8ff�iFt , , um , other iT�dScatibfis'of iAi`�'e�eafe^"�th'�Yii�tvltliem+inbfwat�. The trees growing on the slope exhibit leaning and/or bo��cd trunks a'ith severe trunk distortion observed in some areas. Such distortinn of trce trunks is typically an indication of dou�nslope earth mo��ement. Sediments exposed ucer the majority nf the slopr consist of sand, similar to that encountered H�ithin arprosimatel)' b0 feet of the grnund surface atthe locations of borings E[3-1 and E[3-2. The sand exrosed on the surface of ihe slope arpeared loose H�ith areas of small, fresh exposures. 7'hr fresh exposures of sand appeared to be the result of both burrowing animals and small, surficial slumps. Sediments exposed on the surface of the lower portion of the slope, within appru.�imatel� 20 to 30 �ertical fect of the creek at the base of the ravine, consisted preJominantip of wet, organic, peat-like soils. Gmergent seepage was observed on the slope facc hclow Lot 3a in the area of the contact hetween the sand and the peablike soils. Based on the espluration data, it appears likely that this seepage occurs at or slightly below the sand/silt cuntact enc �untered in horing 66-2 at a depth of approximately 80.5 feet. The presence of tl�e distoned tree tninks �nd the small-scale slump features ar . ins�dliil'iry'`'efi^th��#�� Such small-scale slide features are well removed from the pn�roscd huilding areas and thereforc do not present a risk to these structures. In order to c�aluate the potential for larger, deep�seated slope failures and suitable top of slope building sethacl's, a slope stabilit� analysis ti�as conducted using [he computer program Slope/W, Version 5, by Geo-Slope International. The program used the Morgenstern-Price method for ��—.��s ,�x�; ASSOCI.�TED£�1RTHSGENCES.INC. " Page 6 1:l'... Ii �, U�o p.,..cn: �"�11A! tV' 11=}