8102 EVERGREEN WAY Geotech Report 2025-08-04

DevCo, Inc. ES-6516 April 1, 2019 Page 8 Provided the foundations will be supported as prescribed, the following parameters may be used for design: • Allowable soil bearing capacity 5,000 psf* • Passive earth pressure 350 pcf (equivalent fluid) • Coefficient of friction 0.40 Applicable if foundations are supported on either dense, unweathered glacial deposits or two-inch-diameter, clean crushed rock or lean mix atop dense native soils, as verified by ESNW during construction A one-third increase in the allowable soil bearing capacity may be assumed for short-term wind and seismic loading conditions. The above passive pressure and friction values include a factor- of-safety of 1.5. With structural loading as expected, total settlement in the range of one inch and differential settlement of about one-half inch is anticipated. The majority of the settlements should occur during construction, as dead loads are applied. Seismic Design The 2015 International Building Code recognizes the American Society of Civil Engineers (ASCE) for seismic site class definitions. In accordance with Table 20.3-1 of the ASCE Minimum Design Loads for Buildings and Other Structures manual, Site Class D should be used for design. The referenced liquefaction susceptibility map indicates the majority of the subject site maintains very low liquefaction susceptibility. Liquefaction is a phenomenon where saturated and loose sands suddenly lose internal strength and behave as a fluid. This behavior is in response to increased pore water pressures resulting from an earthquake or other intense ground shaking. Due to the presence of consolidated glacial till and the absence of a uniformly established groundwater table, it is our opinion site susceptibility may be characterized as low. Slab-on-Grade Floors Slab-on-grade floors for the proposed multi-family structures should be supported on well- compacted, firm and unyielding subgrades. Where feasible, native soils exposed at the slab-on- grade subgrade levels can likely be compacted in situ to the specifications of structural fill. Unstable or yielding subgrade areas should be recompacted, or overexcavated and replaced with suitable structural fill, prior to slab construction. A capillary break consisting of a minimum of four inches of free-draining crushed rock or gravel should be placed below each slab. The free-draining material should have a fines content of 5 percent or less (where the fines content is defined as the percent passing the Number 200 sieve, based on the minus three-quarter-inch fraction). In areas where slab moisture is undesirable, installation of a vapor barrier below the slab should be considered. The vapor barrier material should be specifically designed for that use and installed in accordance with the specifications of the manufacturer. Earth Solutions NW, LLC