9702 19TH AVE SE Geotech Report 2024-03-28

Pacific Ridge — DRH, LLC ES-7829.01 August 26, 2021 Page 9 Imported soil intended for use as structural fill should be evaluated by ESNW during construction. The imported soil must be workable to the optimum moisture content, as determined by the Modified Proctor Method (ASTM D1557), at the time of placement and compaction. During wet weather conditions, imported soil intended for use as structural fill should consist of a well-graded, granular soil with 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). Wet-Season Grading If earthwork activities occur during wet weather, additional drainage measures, cement treatment of native soil, and/or the use of select fill material will likely be necessary. Additionally, measures to protect structural subgrades should be considered if exposed during wet weather. Site specific recommendations can be provided at the time of construction and may include leaving cut areas several inches above design subgrade elevations, covering working surfaces with crushed rock, protecting structural fill soil from adverse moisture conditions, and additional TESC recommendations. ESNW can assist in obtaining a wet-season grading permit if required by the governing jurisdiction. Void Space Restoration The process of removing the existing structures may produce voids where old foundations are removed and where crawl space areas may have been present. Complete restoration of voids from old foundation areas must be executed as part of the subgrade preparation activities. The following guidelines for preparing subgrade areas should be incorporated into the 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 exposed at the design 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 The proposed structures can be supported on conventional spread and continuous footings bearing on undisturbed competent native soil, compacted native soil, or new structural fill placed on competent soil. Due to the high moisture sensitivity of the site soils, foundation subgrade areas should be protected from wet weather or areas of remediation should be anticipated; a layer of crushed rock can be considered to protect foundation subgrade areas. If structural building pads are disturbed during wet weather, remediation measures such as cement treatment or overexcavation and replacement with rock may be necessary in some areas. Earth Solutions NW, LLC