615 75TH ST SE Geotech Report 2022-10-25

Subsurface Exploration, Geologic Hazard, and Boardwalk Condominium, Building C Geotechnical Engineering Report Everett, Washington Design Recommendations III. DESIGN RECOMMENDATIONS 8.0 INTRODUCTION It is our opinion that, from a geotechnical standpoint, subsurface site conditions are suitable for re-support of the existing condominium provided that the recommendations contained herein are properly followed. The near-surface soils consisted of loose fill material. Medium dense to very dense Vashon ice contact soils were encountered below the fill at a depth of approximately 12 feet below existing site grades. Due to restricted site access and the presence of existing loose fills, we recommend the use of small-diameter, driven pipe piles for support of the deck. 9.0 SITE PREPARATION Provided that small-diameter, driven pipe piles are used to support the condominium foundation, we do not anticipate that significant site grading will be required. We anticipate minimal excavation adjacent to portions of the existing condominium foundation during proposed pipe pile installation and any related construction. We anticipate that the new foundations for the deck will be installed at or near existing grades. In our opinion, stable construction slopes should be the responsibility of the contractor and should be determined during construction. Temporary cuts within the fill should be constructed at approximately 1.5H:1V (Horizontal:Vertical). Due to the loose, sandy nature of these soils, some raveling should be expected. At this time, we do not anticipate that cut slopes will be required. 10.0 STRUCTURAL FILL Provided that driven pipe piles are used to support the existing foundation, we do not anticipate that structural fill will be required. If it is determined in the field that small amounts of structural fill are required to make grade, we recommend that a non-organic, free-draining soil be used as fill. Free-draining fill limits the amount of fine-grained material to 5 percent by weight when measured on the minus U.S. No. 4 sieve fraction and at least 25 percent greater than the No. 4 sieve. We recommend that structural fill be placed in maximum 8-inch loose lifts with each lift being compacted to at least 95 percent of the modified Proctor maximum density using ASTM:D 1557 as the standard. September 12, 2012 ASSOCIATED EARTH SCIENCES, INC. FSM/!d-EE120288A8-Projects{201202881EDWP Page 9