2721 WETMORE AVE MARQUEE APARTMENTS Geotech Report 2023-06-22

Subsurface Exploration, Geologic Hazard,and 2721 Wetmore Preliminary Geotechnical Engineering Report Everett, Washington Preliminary Design Recommendations III. PRELIMINARY DESIGN RECOMMENDATIONS 6.0 INTRODUCTION Our exploration indicates that, from a geotechnical standpoint, the subject site is suitable for the proposed development provided the recommendations contained herein are properly followed. Sediments encountered in the vicinity of the anticipated foundation depth of approximately 15 to 25 feet generally consist of very dense glacially consolidated Vashon lodgement till and possibly Vashon advance outwash. These sediments are capable of providing suitable building support. Given the depth of the planned building excavation and its proximity to the site boundaries and adjacent structures, excavation for the lower building levels will require temporary shoring. Temporary shoring could be provided by conventional tied-back, soldier pile shoring walls or by soil nailing. Very limited areas of groundwater seepage are anticipated within the limits of the excavation so we anticipate the need for minimal, if any, dewatering during construction. The presence of existing structures and utilities in close proximity to the site perimeter should be considered in selecting an appropriate means of temporary shoring. 7.0 SITE PREPARATION Site preparation for the project should include removal of all existing pavement, old foundations, fill, and any other deleterious materials. Existing underground utilities should either be removed or relocated if they are located below the planned building area. Erosion and surface water control should be established around the perimeter of the excavation to satisfy City of Everett requirements. 8.0 TEMPORARY CUT SLOPES In our opinion, stable construction slopes should be the responsibility of the contractor and should be determined during construction. It is not likely that temporary, unsupported cut slopes will be utilized on this project. However, limited slopes from the top of the excavation shoring to the adjacent streets or alley may be required in places. For estimating purposes, we anticipate that temporary, unsupported cut slopes, completed in the unsaturated, loose to medium dense existing fill sediments can be planned at a maximum slope of 2H:1V (Horizontal: Vertical) up to a maximum height of 10 feet. Temporary cuts of similar height in the unsaturated medium dense to very dense Vashon lodgement till and advance outwash can be planned at a maximum slope of 1H:1V. Flatter temporary cut slopes should be planned in areas of groundwater seepage. During construction of excavation shoring, temporary vertical cuts up May 28,2019 ASSOCIATED EARTH SCIENCES, INC. FSM/Id-190168E001-2-Projects\20190168\KE\WP Page 8