615 75TH ST SE Geotech Report 2022-10-25

Subsurface Exploration, Geologic Hazard, and Boardwalk Condominium, Building C Geotechnical Engineering Report Everett, Washington Project and Site Conditions 4.1 Subsurface Conditions Fill Fill consisting of loose to medium dense, moist, light to medium brown and olive to brownish olive, silty sand with few ranging to little amounts of subangular to rounded fine to coarse gravel was encountered to a depth of approximately 71/2 feet below the ground surface at the location of the exploration boring. At a depth of approximately 71/2 feet to approximately 10 feet, we observed a loose mixture of soils similar to those described above but containing an increased amount of organics (rootlets). These soils are interpreted to be topsoil-derived fill. We were not able to determine the bottom depth of these soils due to poor sample recovery from approximately 10 feet to 121/2 feet. However, the soils within the depth range of 10 to 121/2 feet appear to be in a medium dense condition. Due to their low density, the existing fill soils are not suitable for direct foundation support. The fill, where soil moisture is within the compactable range, is considered suitable for reuse as structural fill (if needed). Vashon Ice Contact Deposits Below the fill, our explorations encountered medium dense to very dense, moist to wet, brownish orange to grayish olive colored, interbedded, fine to coarse sand with trace ranging to few amounts of silt, and silty sand with trace amounts of fine subrounded gravel, which we interpret as Vashon ice contact deposits. The ice contact sediments were deposited in close proximity to the Vashon-age glacial ice sheet. These materials have been overridden by the glacial ice sheet. Consequently, these materials are in a very dense condition. The upper 2 feet of this material are generally weathered containing more brownish and orange hues from iron-oxide staining, and are less dense. The medium dense ice. contact deposits at depth are suitable to re-support the building. We reviewed geologic data for the site based on the Preliminary Surficial Geologic Map of the Mukilteo and Everett Quadrangles, Snohomish County, Washington by Mackey Smith, dated 1976. This map indicates that the near-surface sediment in the site vicinity consists of Vashon lodgement till deposits underlain by Vashon advance outwash and older Pre-Fraser deposits to the northwest of the Beverly Lake area. AESI's geologic findings are in general agreement with those of the reverenced geologic map. September 12, 2012 ASSOCIATED EARTH SCIENCES, INC. FSM/Id-EE120288A8-Projects 1201202881EEIWP Page 4