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Memorandum to City of Everett
<br /> February 28, 2022
<br /> Page 2
<br /> Original site grading occurred during the early 1990s when the roadways and development were constructed.
<br /> Based on review of historic photos, it appears the area south of the fence within the center of the landslide
<br /> mass was recently cleared(2018).We observed significant debris(cut wood rounds,stumps,concrete,downed
<br /> trees, yard debris) throughout the eastern portion of the slope within the slide mass and within the recently
<br /> cleared area.This area has a gentler slope than the adjacent native slopes and may contain more fill placed
<br /> during original development.The slope was saturated with standing water during our site visit, and contained
<br /> small pools within the heavy debris area south of the fence line.
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<br /> Photo 3. Looking East from Central Area of Landslide Photo 4.Looking South at Debris on Slope(Discarded
<br /> Wood,Downed Trees,Yard Debris,
<br /> Vegetation within the landslide area includes a few standing large deciduous trees and brush (primarily
<br /> blackberry) and an occasional conifer.We observed numerous large deciduous trees had fallen on the slope
<br /> exposing the root ball and underlying soils. Exposed soils within the depressions appeared to consist of old
<br /> landslide debris and transitional deposits(loose,saturated silt with sand/sand with silt).
<br /> GEOLOGY
<br /> Soils in the immediate vicinity of 59th Street SW and the closest cross street 25th Avenue West, are mapped as
<br /> glacial till (Vashon Till) within the upland area overlying advance outwash (Fraser Glaciation) on the upper
<br /> slopes.Transitional beds(Fraser Glaciation to pre-Fraser)are mapped on the lower slope of Powder Mill Gulch
<br /> (Minard 19821).
<br /> In the Everett area, advance outwash is exposed where the overlying glacial till cap has been eroded away,
<br /> typically within the upper portions of ravines and bluff margins.The outwash deposits typically consist of clean
<br /> fine to medium sand that has been overridden by thousands of feet of ice. They are typically dense to very
<br /> dense and moderately to highly permeable.
<br /> Transitional beds underlying the advance outwash in the site vicinity consist primarily of clayey silt with lenses
<br /> of sand and silty sand in the upper portion of the deposit.The transitional beds and advance outwash layers
<br /> 1 Distribution and Description of Geologic Units in The Mukilteo Quadrangle,Washington,dated 1982 by James P.Minard.
<br /> GeoEngineers,Inc.
<br /> File No.0661-133-00
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