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Geotechnical Engineering Report <br /> Proposed Flight Line Steam Line Project lierracon <br /> ' Boeing Everett Facility• Everett, Washington <br /> January 17, 2012 • Terracon Project No.: 81115085 <br /> EXECUTIVE SUMMARY <br /> A geotechnical investigation has been completed for the proposed Flight Line Steam Line Project <br /> to be located at the Boeing Everett Facility in Everett, Washington. Four(4) borings, designated B- <br /> 1 through B-4, were completed to depths ranging from approximately 18% to 19 feet below the <br /> existing surface along the proposed steam line alignment. <br /> Based on the information obtained from our subsurface exploration, the site is suitable for <br /> development of the proposed project. The following geotechnical considerations were identified: <br /> • Site Soil & Groundwater Conditions: The site is surfaced with about 4% to 7 inches of <br /> ' asphalt and about 8 to 8'/z inches of concrete pavement. The asphalt and concrete pavements <br /> are underlain by a variable thickness of crushed aggregate and asphalt treated base (ATB). <br /> Soil conditions encountered below the existing pavement generally consist of fill soils and <br /> native soils interpreted as glacial till. Fill soils were encountered in the southern portion of the <br /> alignment (borings B-3 and B-4) to depths of approximately 3% and 5'/z feet below existing <br /> grade, respectively. In general, the fill consisted of medium dense sand with trace silt and <br /> gravel. Buried asphalt and ATB were encountered at the bottom of the fill zone in borings B-3 <br /> and B-4, and are interpreted as relic pavements. Glacial till deposits were encountered below <br /> the pavement section in borings B-1 and B-2, and below the existing fill soils in borings B-3 and <br /> B-4. The glacial till deposits extended to the total depth explored of 19 feet below existing <br /> grade. In general, the glacial till consisted of dense to very dense silty sand with to trace <br /> ' gravel. Cobbles and boulders were not encountered in the explorations completed for this <br /> study, but are not uncommon in glacial till deposits. <br /> Slight groundwater seepage was observed in borings B-3 and B-4 at depths of <br /> approximately 3 and 51/4 feet below the surface, respectively. The observed groundwater <br /> seepage is interpreted to represent water perched within existing fill soils located above <br /> ' lower permeability glacial till soils. We understand that pothole explorations completed by <br /> the contractor encountered moderate groundwater seepage near existing utility trenches. <br /> ' Given the relatively low permeability of the site glacial till soils, perched groundwater may <br /> develop above the till, within sandy zones within the till, and within pip bedding during <br /> periods of extended wet weather. <br /> ' • Seismic Site Classification: Per Table 1613.5.2 of the 2009 International Building Code <br /> (IBC), the seismic site classification for this site is C. The risk of seismic induced liquefaction <br /> settlement is low. <br /> • Foundations: Conventional spread footings and mat foundations will provide adequate <br /> support for the proposed utilidor provided that foundation subgrades are properly prepared. <br /> Foundation support for the utilidor may be obtained from the existing dense to very dense <br /> glacial till soils. Utilidor foundations should be supported on a minimum 6-inch thick working <br /> 1 Responsive • Resourceful • Reliable <br />