13 46TH ST SW 2016-01-01 MF Import

� DAVID L. NELSON AND ASSOCIATES, INC. � Consulting Engineerin�; Geolagy October 6, 1992 Project No. 9892 � Page 4 Steep Slope and Landslide Hazard � The steep slopes cored by native soils are stable with respect to deep seated failures. These slopes are considere�i margina] 7 '; � stable with respect to the native soils in a loose condi.t5 ;, , creating "normally" stable slopes at 2H: 1V, or flatter. Therefore, some soil creep and local surface sloughing i: � expected on the steeper portions of the slope (steeper t:�r:r� � 2H: 1V) with respect to time. The effect of this surface • sloughing on the structure is reduced by apprbpriate setbacks or �� extending the foundations into the native soils that underlies I , j the size. ! �"' Steps should be taken in the development and construction in the � proposed residence area to reduce the risk of any potential slope instability. These include: 1. Fill should not be placed on or near the top of slope. I� 1 This includes yard waste and landscaped planters. R, � 2 . Drainage should be routed away from the top of slope � ; and into an appropriate drain system, j•� ., i : 3. Vegetation should not be disturbed on the slope. Any � � distur.bed vegetation should be replanted and maintained �� until it is established. Pruning of vaqetation, if � perfor,�ed, should be removed from the slope and any I � � root bundles left in place. Seismic Hazard �� � �,.� �.� The Puget Sound reyion is classified as a zone 3 by the Uniform Building Code. Seismic considerations for residential �� construction include liquefaction potential and attenuation of I " � ground motions by soft soil deposits. Typically, seismic hazards �� are hiqhest for thick alluvial (organic and/or normally consolidated) soils. The liquetaction potential is highest for ( 1 loose sand and silty sand deposits with a high ground water � table. The thickness of the sand depos3.t should be considered, as liquefaction is dependent on the ability of excess pore �p � pressures to dissipate. That is, if the deposit is relatively thin with a short drainage path, the pore pressures can dissipate ' I fairly rapidly. " ' No deposits which are considered seismic sensitive were E �� encountered on site above the outcropping qround water "line" . The surface saturated soils below this line may loose strength � �� � during a seismic event, creating local surface slides to occur. � 1 ' �: --- i, � �.=� ��, � - � � - -�.�