8417 EVERGREEN WAY Geotech Report 2022-10-25

Geotechnical Engineering Report-Revised lierracon Proposed CFT Retail • Everett,Washington February 1, 2018 ■Terracon Project No. 81185002 Groundwater level fluctuations are expected to occur due to seasonal variations in the amount of rainfall, runoff, and other factors not evident at the time the borings were performed. In addition, perched water can develop over low-permeability soil, but may not be present after long periods of dry weather. Therefore, groundwater levels during construction or at other times in the life of the structure may be higher or lower than the levels indicated on the boring logs. 4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION 4.1 Geotechnical Considerations Based on the results of our explorations, the site appears suitable for the proposed construction supported by conventional shallow spread footings provided that footings extend at least to a depth consistent with the top of competent soil and/or certain subgrade improvements are implemented. Geotechnical engineering recommendations for foundation systems and other earthwork- connected phases of the project are outlined below. The recommendations contained in this report are based upon the results of data presented herein,engineering analyses,and our current understanding of the proposed project. ASTM and Washington State Department of Transportation (WSDOT) specification codes cited herein respectively refer to the current manual published by ASTM International and the 2016 edition of the WSDOT Standard Specifications for Road, Bridge, and Municipal Construction (Publication M41-10). The soils onsite within the project limits are comprised of moderate silt content. Precaution should be taken when construction is performed during wet weather.The higher silt content soils at the site may be sensitive to moisture and will make for difficult earthwork and construction during wet weather. Previous site activities include grading of the gently sloped site. The southwestern and southeastern portions of the site consist of a relatively thick fill layer, which ranges to depths between 4.5 and 7 feet on our borings. Our exploratory borings indicated that this fill layer was loose in relative density. Settlement and cracking of the asphalt overlying this fill layer was observed primarily in the southwest and southeast portions of the site. Fill was observed in all exploratory soil borings performed onsite with estimated thickness of up to 7 feet. Thicker layers of fill were observed between the central and southern portions of the site. By nature, fill can be highly variable and could vary between sample locations. Support of footings,floor slabs, and pavements on or above existing fill soil is discussed in this report. There is an inherent risk for the owner that compressible fill or unsuitable material within or buried by the fill will not be discovered. This risk of unforeseen conditions cannot be eliminated without completely removing the existing fill, but can be reduced by performing additional testing and evaluation. Responsive ■ Resourceful a Reliable 4