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Geotechnical Engineering inNort Irerracon <br /> SN4924—Silver Lake North Cell Tower Everett, Washington <br /> October 24, 2014 Terracon Project No. 81145043 <br /> EXECUTIVE SUMMARY <br /> A geotechnical exploration has been performed for the SN4924 Silver Lake North tower site to be <br /> constructed at 8110 104TH Street SE in Everett, Washington. Terracon's geotechnical scope of <br /> work included the advancement of one test boring to an approximate depth of 41.5 feet below the <br /> existing ground surface (bgs). <br /> Based on the information obtained from our subsurface exploration, the site is suitable for the <br /> proposed project. The following geotechnical considerations were identified: <br /> Subsurface Conditions: Soils encountered generally consisted of approximately 5 feet of <br /> medium dense silty sand with trace gravel (weathered glacial till), underlain with 36.5 feet of <br /> dense to very dense silty sand with gravel (glacial till). Groundwater was encountered at <br /> approximately 15 feet bgs during drilling. <br /> Foundations: The proposed monopole tower may be supported on either a reinforced <br /> concrete mat foundation bearing on the native medium dense to very dense silty sand soils, or <br /> a drilled shaft foundation with a minimum length of 10 feet. Based on mapped geologic <br /> conditions and our field observations, the presence of scattered large cobbles or boulders <br /> could potentially cause difficulty during construction of a drilled shaft foundation. <br /> Close monitoring of the construction operations discussed herein will be critical in achieving the <br /> design subgrade support. We therefore recommend that Terracon be retained to monitor this <br /> portion of the work. <br /> This summary should be used in conjunction with the entire report for design purposes. It should <br /> be recognized that details were not included or fully developed in this section, and the report <br /> must be read in its entirety for a comprehensive understanding of the items contained herein. <br /> The section titled GENERAL COMMENTS should be read for an understanding of the report <br /> limitations. <br /> Responsive■ Resourceful■ Reliable i <br />