3500 TERMINAL AVE Geotech Report 2022-10-25

Port of Everett—South Terminal Wharf& Electrical Upgrades—Phase 2 13 The conclusions and analyses in this report are based on subsurface soil and groundwater conditions interpreted from these boring explorations.The nature and extent of variations between the exploration locations and current conditions may not become evident until construction begins or additional explorations are performed. If variations are encountered, it may be necessary to reevaluate the conclusions and recommendations in this report. Soil Conditions The near-surface conditions of the site consist largely of non-native material due to the construction of the gravel containment dike and the placement of dredged,granular fill upland of the dike.The native, underlying soil in the area is comprised predominantly of loose to dense silty sand,with scattered, relatively thin layers of soft silt, underlain by stiff to very hard,glacially overridden silt and clay. We divided the site soils into various Engineering Soil Units (ESU) based on the general geotechnical engineering properties.Table 1 describes the ESUs and their pertinent geotechnical engineering parameters. Friction angles were based on (N1)60 correlations provided in the WSDOT Geotechnical Design Manual (GDM), section 5.8.3 (WSDOT 2016). CPT based interpretations were done with the software CpeT-IT. We generated soil cross-sections at several locations throughout the site that show approximate stratification profiles of these ESUs(Figures 3,4, 5, and 6).These cross-sections include boring logs and CPT profiles, which were used to approximate the soil profiles, and also indicate which soils are potentially liquefiable. The locations of these cross-sections are shown on Figure 2. Table 1 — Summary of Engineering Soil Units Effective Average Unit Weight Potentially ESU Friction Angle (N1)60 (pcf) Liquefiable? (degrees) 1 22 115 31 Yes 2 27 125 35 No 3 15 115 20 No 4 46 125 38 No 5 4 110 N/A Yes 6 11 120 32 Yes 7 28 125 38 Yes 8 40 130 40 No 9 62 130 40 No The soil conditions can be generally categorized using the ESUs described below. ESU 1. Consists of loose to medium-dense silty gravelly Sand and sandy Gravel.This material was placed as dredged fill during construction of the Weyerhaeuser Mill and is located behind the construction dike.The unit is approximately 20 to 30 feet thick and is potentially liquefiable below the groundwater table. liJI 19232-01 HARTc OIWSER December 6,2017