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Geotechnical Engineering Report lierracon <br /> Proposed Flight Line Steam Line Project <br /> Boeing Everett Facility Everett, Washington <br /> January 17, 2012 Terracon Project No.: 81115085 <br /> The Distribution and Description of Geologic Units, Mukilteo, Washington (USGS Map MF-1438, <br /> 1982) maps the site as being mantled by Quaternary Vashon Glacial till deposits. The till <br /> deposits are described as primarily consisting of poorly sorted, non-stratified mixture of clay, silt, <br /> sand, pebbles, and cobbles with occasional large boulders. The soils encountered on site <br /> below the pavement section and fill appear to be representative of the glacial till deposits. <br /> 3.2 Groundwater I <br /> Slight groundwater seepage was observed in borings B-3 and B-4 at depths of approximately 3 <br /> and 51/4 feet below the surface, respectively. The groundwater seepage observed in the borings I <br /> is interpreted to represent water perched within existing fill soils located above lower <br /> permeability glacial till soils. Given the relatively low permeability of the site glacial till soils, <br /> perched groundwater may develop above the till or within sandy zones within the till during I <br /> periods of extended wet weather. <br /> We understand that pothole explorations completed by the contractor encountered moderate , <br /> groundwater seepage near existing utility trenches. Perched groundwater within utility trench <br /> backfill and pipe bedding should be anticipated. <br /> These observations represent groundwater conditions at the time of the field exploration. <br /> Groundwater conditions should be expected to fluctuate due to changes in season, precipitation <br /> patterns, site utilization, on-site or off-site irrigation activities, and other on- and off-site factors. <br /> 4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION <br /> 4.1 Geotechnical Considerations 1 <br /> Based on our subsurface exploration program and associated research, we conclude that the <br /> proposed steam line utilidor project is feasible from a geotechnical standpoint, contingent on <br /> proper design and construction practices. <br /> Geotechnical engineering recommendations for the project are outlined below. The <br /> 9 9 <br /> recommendations contained in this report are based upon the results of field and laboratory <br /> testing (which are presented in Appendices A and B), engineering analyses, and our current 111 <br /> understanding of the proposed project. ASTM and Washington State Department of <br /> Transportation (WSDOT) standard specifications cited herein respectively refer to the 2010 <br /> manual published by the American Society for Testing & Materials and the current edition of the <br /> Standard Specifications for Road, Bridge, and Municipal Construction (M41-10). <br /> 1 <br /> I <br /> Responsive • Resourceful • Reliable 4 <br /> I <br />