1618 HOLBROOK AVE 2018-01-02 MF Import

Retaining Wall Letter Lyashuk Residence, Everett, WA January 29, 2007 NGA File No. 755806 Page 5 (IH:9V) back toward the cut. The wall batter should be accomplished by inclining the subgrade excavation back toward the cut to tilt the base coarse of blocks as they are placed. The back of the block should be 3.3 inches deeper than the front of the block. The ultra blocks could be placed on a crushed rock pad, that has been compacted to it non -yielding condition before placing the blocks. All vertical joints between blocks should be staggered at each row, which may require several half-length blocks for the wall construction. A drainage blanket consisting of it minimum of 12 inches of free -draining rock or rock spalls should be placed between the blocks and the face of the native soil in the cut. A rigid 4-inch diameter perforated drainpipe embedded in it minimum of one -foot of washed rock and wrapped in a filter fabric should be placed at the bottom of the drainage blanket behind the base of the bottom course of blocks. The pipe should be sloped to drain into a permanent discharge outlet. IConcrete Retaining Walls I Retaining walls will be incorporated into project plans in the form of daylight basement walls. The t lateral rressure acting on subsurface retaining walls is dependent on the nature and density of the soil behind the wall, the amount of lateral wall movement which can occur as backfill is placed, wall drainage cnuditions, the inclination of the backfill, and other possible surcharge loads. For walls that are free to yield at the top at least one thousandth of the height of the wall (active conditionl, soil pressures will be lless than if movement is limited by such factors as wall stiffness or bracing (at -rest condition). The I planned southern retaining wall should be designed using a triangular earth pressure distribution equivalent to that exerted by a fluid with it density of 40 pcf for it yielding condition, and 60 pcf for non - yielding condition. These recommended lateral earth pressures are for a drained granular backfill. We could consult with you and your structural engineer regarding additional loads on retaining walls during final design, if needed. We have also recommended that the concrete wall extend at least two feet above the finished ground surface to provide a catchment area for any material that may slough from the slope. We recommend that the above grade section of the wall be designed using it triangular pressure distribution equivalent to that exerted by a fluid with a density of 100 pcf. The lateral pressures on walls may be resisted by friction between the foundation and subgrade soil. and by passive resistance acting on the below -grade portion of the foundation. A coefficient of friction of 0.35 may be used to calculate the base friction and should be applied to the vertical dead load only. NELSON GEOTECHNICAL ASSOCIATES, INC.