4003 NASSAU PL 2016-01-01 MF Import

� . Geotechnical Engineering heport Kvernmo Single-Family Residence � 4003 Nassau Place, Everett September 17, 2002 NGA File No. 356102 � Page 13 sand blanket may be used to cover the vapor barrier. The purpose of this sand blanket is to protxt the ' vapor barrier membrane and to aid in curing the concrete. 1 ' Retaining Walls and Lateral Pressures Lateral earth pressures acting on retaining walls will depend on the nature and density of the soil behind the wall, the amowit of lateral wali movement that can occur as backfill is placed, and the inclination of the backfill. WaUs that are fm to yield at least one-thousandth of the height of the wall are in an "active" I condition. Walls restrsined from movement by stiffness or bracing are in an "at rest;' condition. Active earth pressures and at-rest earth prcssum can be calculated based on equivalent fluid density. Equivalent fluid densities for active and at-rest earth pressure of 45 pounds per cubic foot (pc� and 65 pcf, respectively, may be used for design for a level backslope. These values assume that the granular � soils are used for backfill and that the backfill adjacent to the walls is drained. The preceding values do not include the effects of surcharges such as due to foundation loads, traffic, or other surface loads. � Surcharge effects should be considered where appropriate. For passive pressure on the wall foundation refer to the I.ateral Lords subsection of this report. , � All wall backfill should be well compacted. Care should be taken to prevent the buildup of excess lateral soil pressures due to overeompaction of the wall backfill. This can be accomplished by placinb wall � backfill in S-inch-thick lifts within a distance equal to one-half the height of the wall. Compaction close to the wall and within this zone can be accomplished with small, hand-operated compactors. Permanent drainage systems should be installed for retaining walls as described in the Sub�urface Draieage subsection of this report. Site Drainage Surface Draioage: Water should not be allowed to stand in any area where footings, slabs or pavements � are to be constructed. Final site grades should allow for drainage away from the residence. We suggest that the finished ground be sloped at a gradient of 3 percent minimum for a distance of at least 10 feet away from the structure. Surface water should be collected by permanent catch basins and drain lines and be discharged into a stortn drain system. Runoff should not be allowed to concentrate or flow over the slope. Surface drains should be maintained separately and not be interconnected with foundation or wall drains. NELSON GEOTECHNICAL ASSOCIATES, INC.�1 , 4�