10901 27TH AVE SE Geotech Report 2025-07-29

1 ' Subsurface E.eploration, Geologic Hazards, and Proposed Jaynes Monroe Elementary School Replacement Revised Geotechnical Engineering Report Everett, Washington Design Recommendations ' III. DESIGN RECOMMENDATIONS 8.0 INTRODUCTION INT TI N ' The site is underlain by native soils consisting of dense to very dense lodgement till. 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 in our exploration borings was up to approximately 5 feet below existing grade. 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 restore planned elevations. Reuse of on-site soils for structural fill may require aeration and drying to reduce moisture contents at the time of construction. ' Below areas of planned paving, it would be possible to leave existing fill in place with some remedial preparation. We recommend that paving areas be stripped of existing topsoil, and ' proof-rolled and compacted as described later in this report for preparation of paving subgrades. If the resulting surface is firm and unyielding and compacted to 95 percent or more of the modified Proctor maximum dry density, no further preparation is required. If the ' subgrade is wet or yielding, we recommend that a portion of the existing fill be removed and replaced with material that is capable of being compacted under field conditions that are October.5, 2009 ASSOCIATED EARTH SCIENCES, INC. 13WWG/1d-KE090.312A3-Project sL00903121KE1WP Page 1 1 1