3214 BROADWAY SEPA 017 - 004 Geotech Report 2025-04-14

American Property Develov.nent ES-0599.05 January 16, 2015 Page 5 Updated January 22, 2015 This geotechnical engineering study has been prepared for the exclusive use of American Property Development and their representatives. The study has been prepared specifically for the subject project. No warranty, expressed or implied, is made. This study has been prepared in a manner consistent with the level of care and skill ordinarily exercised by other members of the profession currently practicing under similar conditions in this area. Site Preparation and Earthwork The primary geotechnical considerations with respect to earthwork are related to the proposed building's excavation, temporary slope construction, temporary excavation support, and foundation subgrade preparation. The soils encountered in the building excavations should largely consist of dense to very dense silty sand deposits. These soils should generally be suitable for use as structural backfill, where needed. The native soils can be characterized as having a generally moderate sensitivity to moisture. Therefore, if the soils are exposed to excessive moisture, successful placement and compaction of the soil may be difficult. Excavations As excavation of the proposed building progresses, the soil relative density should generally increase and is expected to exhibit good stability in open cut excavations. Overall stability of the excavation is anticipated to be good, provided appropriate means for sloping and shoring the excavation are utilized. Based on the soil conditions observed at the test sites, the following allowable temporary slope inclinations can be used: • Upper 4 Feet of Excavation 1 H:1 V (Horizontal:Vertical) • Below 4 Feet 0.5H:1V to 0.75H:1V The geotechnical engineer should observe the excavation and assess the allowable temporary slope inclination based on the soil and groundwater conditions exposed in the excavation. Supplement recommendations for sloping the excavation may be made by the geotechnical engineer based on conditions observed. With respect to temporary shoring, recommendations are provided in the Shoring Recommendations section of this study. Structural Fill We anticipate structural fill placement will generally be required behind foundation walls and within utility trench excavations. Structural fill may also be necessary in slab-on-grade areas. Where structural fill is necessary below the proposed building foundations, a suitable crushed rock material should be used. In our opinion, clean crushed rock consisting of one and one half inch to two inch aggregate should be used below foundations where fill placement is necessary. Earth Solutions NW, LLC