3500 TERMINAL AVE Geotech Report 2022-10-25

4 I Port of Everett—South Terminal Wharf& Electrical Upgrades—Phase 2 ESU 2.Consists of medium-dense to dense Gravel.This unit comprises the existing construction dike,and appears to extend from elevations of approximately 15 to-55 feet. ESU 3.Consists of native soft to medium-stiff Clay and silty Clay.This unit is generally found to underlie ESU 1,and was detected only in CPT-3,where an approximately 5-foot-thick layer was encountered.This unit is found at elevations higher than-40 feet. It appears that this material was not removed as part of the previous dredging activities and extends below the existing construction dike. ESU 4.Consists of medium dense to dense silty Sand.This unit appears to extend throughout the site,and in various locations underlies the dredged fill (ESU 1)and construction dike(ESU 2).This unit ranges in thickness from approximately 30 feet to 80 feet at boring locations,with the depth of this unit generally increasing to the south.This layer is generally considered a suitable bearing layer for deep foundation elements at the south end of the wharf. ESU 5.Consists of very soft,very sandy Silt.This unit was encountered in the borings near the west side of the pier,close to the toe of the construction dike.The layer ranges in thickness from 5 to 12 feet.Similar to ESU 3, it appears that this material was not removed as part of the previous dredging activities and extends below the existing construction dike.This unit is potentially liquefiable. ESU 6.Consists of loose to medium dense silty Sand.This unit is encountered below elevations ranging from approximately-25 to-75 feet.Thickness of this layer ranges from approximately 5 to 30 feet at boring locations.This unit is potentially liquefiable. ESU 7.Consists of medium-dense Sand and silty Sand.This unit is encountered in pockets in the upland area of the site, underlying the dredged fill.The thickness of this unit ranges from approximately 5 to 10 feet at boring locations.This unit is potentially liquefiable. ESU 8.Consists of very stiff to hard Silt and Clay with pockets of silty Sand and Gravel.This unit exhibits till- like behavior.The depth of the top of this unit generally increases to the north.Generally,all deeper explorations terminated in this layer.This layer is generally considered a suitable bearing layer for deep foundation elements. ESU 9.Consists of hard sandy Silt with Gravel.This soil unit is found below elevations of approximately- 120 feet,and is likely glacial till.This unit has high strength and low compressibility,and is a suitable bearing layer for deep foundation elements. Groundwater Groundwater measurements were taken on August 17th,2016 at two monitoring wells at the site, showing groundwater elevations of approximately+3 to+5 feet MLLW.A second measurement was taken at monitoring well 1 on December 8th,2016,showing an elevation of+10.2 feet MLLW.The results are summarized in Table 2. Because of the site's close proximity to Possession Sound and Port Gardner Bay, historical tidal information for the area was also evaluated to characterize groundwater patterns. High tidal elevations in Everett range from about+11.4 ft in September to about+12.9 ft in December; low tidal elevations range from about 0 ft in March to-3 ft in June.These tidal data are consistent with the data 19232-01 1111111 December 6,2017 H411TOtOwSER