917 112TH ST SE Geotech Report 2022-10-25

Habitat for Humanity of Snoh mish County ES-5168 April 26, 2017 Page 6 Subgrade Preparation Following site stripping and removal of existing structures and outbuildings, cuts and fills will be completed to establish proposed subgrade elevations across the site. ESNW should observe the subgrade(s) during initial site preparation activities to confirm soil conditions are as anticipated and to provide supplementary recommendations for subgrade preparation, as necessary. The process of removing existing structures may produce voids where old foundations and/or crawl space areas may have been present. Complete restoration of voids resulting from demolition activities must be executed as part of overall subgrade and building pad preparation activities. The following guidelines for preparing building subgrade areas should be incorporatedintothe final design: • Where voids and related demolition disturbances extend below planned subgrade elevations, restoration of these areas should be completed. Structural fill should be used to restore voids or unstable areas resulting from the removal of existing structural elements. • Recompact, or overexcavate and replace, areas of existing fill, if present, exposed at building subgrade elevations. Overexcavations should extend into competent native soils and structural fill should be utilized to restore subgrade elevations as necessary. • ESNW should confirm subgrade conditions, as well,as the required level of recompaction and/or overexcavation and replacement, during site preparation activities. ESNW should also evaluate the overall suitability of prepared subgrade areas following site preparation activities. Foundations In our opinion, the proposed residential structures may be constructed on conventional continuous and spread footing foundations bearing upon competent native soil, recompacted native soil, or new structural fill. In general, competent native soil suitable for support of foundations will likely be encountered beginning within the upper two to three feet of existing grades'. Where loose or unsuitable soil conditions are exposed at foundation subgrade elevations, compaction of soils to the specifications of structural fill, or overexcavation and replacement with suitable structural fill, will be necessary. Provided the foundations will be supported as prescribed, the following parameters may be used for,design: • Allowable soil bearing capacity 2,500 psf • Passive earth pressure 350 pcf(equivalent fluid) • Coefficient of friction 0.40 Earth Solutions NW,LLC