3003 W CASINO RD BLDG 45-06 Geotech Report 2025-03-03

Geotechnical Engineering Report lierracon 1 Proposed Flight Line Steam Line Project Boeing Everett Facility • Everett, Washington January 17, 2012 ■ Terracon Project No.: 81115085 The seismic performance of the utilidor was evaluated relative to seismic hazards resulting from ground shaking associated with a design seismic event with a 2,500-year return period I determined in accordance with the 2009 International Building Code (IBC). The results of our seismic hazard analyses and recommended seismic design parameters are presented in the following sections. 4.3.2 Ground Surface Rupture The site is within the mapped trace of the Quaternary age Whidbey Island fault zone. The Whidbey Island fault zone is a collective term for a complex series of northwest trending fault splays. The fault zone is about 5 to 7 kilometers wide and extends from the Mukilteo area northwest into the eastern portions of the Strait of Juan de Fuca. Most of the fault zone is concealed by Holocene glacial and post glacial deposits, and marine sediments, and is primarily mapped based on the location of gravity and magnetic anomalies and off shore seismic reflection data. There is no historic information regarding movement on the Whidbey Island fault zone. Inferred quaternary strata are reportedly folded and faulted by strands of the southern portion of the fault zone in off shore seismic reflection data. On land, the youngest strata cut by the fault zone appear to be 80 to 125 thousand year old Whidbey Formation deposits. Given the limited fault history data, the USGS has concluded that there is insufficient information to infer a recurrence interval for earthquakes on the Whidbey Island fault zone. Based on the currently available information, it appears that the risk of damage to the proposed utilidor due to ground surface rupture is low and comparable to the risk to the existing site facilities. 4.3.3 Landsliding , Based on the relatively level nature of the site and the dense to very dense nature of the glacial till foundation soils, it is our opinion that the risk of earthquake-induced Landsliding is low. 4.3.4 Soil Liquefaction Liquefaction is a phenomenon wherein saturated cohesionless soils build up excess pore water , pressures during earthquake loading. Liquefaction typically occurs in loose soils, but may occur in denser soils if the ground shaking is sufficiently strong. Based on the dense to very dense nature of the site glacial till soils, and the limited perched groundwater conditions, it is our opinion that the risk of seismic induced settlement is low. Lateral spreading is a phenomenon in which soil deposits which underlie a site can experience , significant lateral displacements associated with the reduction in soil strength caused by soil liquefaction. This phenomenon tends to occur most commonly at sites where the soil deposits can flow toward a "free-face", such as a water body. Due to the lack of liquefiable soils at the site and the lack of a "free-face" condition, it is our opinion that the risk of lateral spreading at the site is low. , 1 Responsive • Resourceful • Reliable 12