8102 EVERGREEN WAY Geotech Report 2025-08-04

DevCo, Inc. ES-6516 April 1, 2019 Page 7 Subgrade Preparation Competent, uniform subgrade areas should be established below the foundation and slab elements to both minimize the potential for differential settlement and provide competent bearing conditions along structural subgrades. Where dense subgrade conditions are exposed at proposed subgrade elevations, minimal preparations will likely be necessary. ESNW should confirm acceptability of subgrade areas prior to placing formwork. Supplementary recommendations for subgrade improvement may be provided at the time of construction; such recommendations would likely include overexcavation and replacement with clean crushed rock or lean mix (foundation subgrade). 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. 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. Structural Fill Structural fill is defined as compacted soil placed in foundation, slab-on-grade, roadway, permanent slope, retaining wall, and utility trench backfill areas. Soils placed in structural areas should be placed in loose lifts of 12 inches or less and compacted to a relative compaction of 95 percent, based on the laboratory maximum dry density as determined by the Modified Proctor Method (ASTM D1557). For soil placed inutility trenches underlying structural areas, compaction requirements are dictated by the local city, county, or utility district, and are typically specified to a relative compaction of at least 95 percent. Structural fill placed below foundation elements in heavier load areas must consist of two-inch diameter, clean crushed rock or lean mix placed directly atop dense native soils. Foundations Based on our findings, it is our opinion the proposed multi-family structures may be constructed on conventional continuous and spread footing foundations bearing upon dense to very dense native soil. In general, dense native soil suitable for support of foundations will likely be encountered beginning at depths of about two-and-one-half to eight feet bgs. Where loose or unsuitable soil conditions are exposed at foundation subgrade elevations, overexcavation to a depth that exposes dense native soil and replacement with crushed rock or lean mix will be necessary. Earth Solutions NW, LLC