9606 19TH AVE SE PREMIER STORAGE Geotech Report 2022-10-25

Premier Storage Everett, LLC ES-2432 June 26, 2012 Page 9 Revised June 28, 2012 Slab-On-Grade Floors Slab-on-grade floors for proposed storage buildings constructed at this site should be supported on a firm and unyielding subgrade. Where feasible, the existing fill soils exposed at the slab-on-grade subgrade level can be compacted in place to the specifications of structural fill. Unstable or yielding areas of the subgrade should be recompacted or overexcavated and replaced with suitable structural fill prior to construction of the slab. Given the loose fill soils present on the site, areas of the slab subgrade will likely require stabilization measures. A capillary break consisting of a minimum of four inches of free draining crushed rock or gravel should be placed below the slab. The free draining material should have a fines content of 5 percent or less (percent passing the #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. If a vapor barrier is to be utilized it should be a material specifically designed for use as a vapor barrier and should be installed in accordance with the manufacturer's specifications. Retaining Walls Retaining walls must be designed to resist earth pressures and applicable surcharge loads. The following parameters can be used for retaining wall design: • Active earth pressure (yielding condition) 35 pcf(equivalent fluid) • At-rest earth pressure (restrained condition) 50 pcf • Traffic surcharge for passenger vehicles 70 psf(rectangular distribution) (where applicable) • Traffic surcharge for trucks 100 psf(rectangular distribution) (where applicable) • Passive resistance 350 pcf(equivalent fluid) • Coefficient of friction 0.4 • Lateral seismic surcharge (yielding conditions) 6H (where H equals retained height) Additional surcharge loading from adjacent foundations, sloped backfill, or other loads should be included in the retaining wall design. Drainage should be provided behind retaining walls such that hydrostatic pressures do not develop. If drainage is not provided, hydrostatic pressures should be included in the wall design. Earth Solutions NW,LLC