202 ALDER ST Geotech Report 2025-07-30 (2)

• Proposed View Ridge Subsurface Exploration, Geologic Hazards, Infiltration Potential, Elementary School Replacement and Preliminary Geotechnical Engineering Report Everett, Washington Preliminary Design Recommendations III. PRELIMINARY DESIGN RECOMMENDATIONS 8.0 INTRODUCTION The site is underlain by native soils consisting of dense to very dense advance outwash sediments. These materials are suitable for structural support with proper preparation. Some portions of the site are underlain by a layer of surficial existing fill that is loose and variable. Existing fill should be removed and recompacted where it occurs below planned buildings, and warrants remedial preparation where it occurs below paving and similar lightly loaded structures. 9.0 SITE PREPARATION Erosion and surface water control should be established around the clearing limits to satisfy local requirements. Existing buildings, foundations, floor slabs, paving, buried utilities, vegetation, topsoil, and any other deleterious materials should be removed where they are located below planned construction areas. All disturbed soils resulting from demolition activities should be removed to expose underlying, undisturbed native sediments and replaced with structural fill, as needed. All excavations below final grade made for demolition activities should be backfilled, as needed, with structural fill. Once demolition has been completed, existing fill should be addressed. The observed fill depth iri our exploration borings was up to approximately 10 feet below existing grade. It seems likely that fill observed on-site was associated with existing utilities (EB-1), backfill of existing foundations (EB-6 and EB-7), and an area of visually conspicuous fill between the existing parking area and building (EB-3). Of these areas of observed existing fill, only the fill around EB-3 appears to be laterally and vertically extensive and at the location of a planned new building. We recommend that existing fill be removed from below areas of planned foundations to expose underlying, undisturbed native sediments, followed by restoration of the planned foundation grade with structural fill. Removal of existing fill should extend laterally beyond the building footprint by a distance equal to the depth of overexcavation. For example, if existing fill is removed to a depth of 2 feet below a planned footing area, the excavation should also extend laterally 2 feet beyond the building footprint in that area. Where existing fill is removed and replaced with structural fill, conventional shallow foundations may be used for building support. If earthwork for the project is completed in dry site and weather conditions, we anticipate that the excavated existing fill material can be recompacted as structural fill to September 22, 2010 ASSOCIATED EARTH SCIENCES, INC. DWG/tb-KE10025542-Projects1201002551KEIWP Page 12