5816 25TH AVE W Geotech Report 2025-06-25

Kierstein Residence Retaining Wall Everett, Washington Geotechnical Engineering Report This test and sampling method consists of driving a standard 2-inch, outside-diameter, split-barrel sampler a distance of 18 inches into the soil with a 140-pound hammer free-falling a distance of 30 inches. The number of blows for each 6-inch interval is recorded, and the number of blows required to drive the sampler the final 12 inches is known as the Standard Penetration Resistance ("N") or blow count. If a total of 50 is recorded within one 6-inch interval, the blow count is recorded as the number of blows for the corresponding number of inches of penetration. The resistance, or N-value, provides a measure of the relative density of granular soils or the relative consistency of cohesive soils; these values are plotted on the attached exploration boring log. The samples obtained from the split-barrel sampler were classified in the field and representative portions placed in watertight containers. The samples were then transported to our laboratory for further visual classification. SUBSURFACE CONDITIONS Subsurface conditions on the project site were inferred from the field explorations conducted for this study, visual reconnaissance of the site, and a review of applicable geologic literature. As shown on the field logs, a general sequence of soils encountered at the site consisted of fill and Vashon-age advance outwash sand and gravel. The deposits encountered at the site are in general agreement with the published geologic map of the site area titled Distribution and Description of Geologic Units in the Mukileo Quadrangle, Washington, by James P. Minard dated 1982. The geologic map indicates the site is located near the contact between Vashon-age lodgement till and the underlying, older Vashon-age advance outwash. The following section presents more detailed subsurface information on the soil units encountered at the site. The interpreted subsurface distribution of the soil units described below is presented in Figure 3 (Geologic Cross-Section A-A'). The location of the cross-section is shown on Figure 2 (Site and Exploration Plan). Stratigraphy Quaternary Landslide Debris (Fill) Fill soils (those not naturally placed), were encountered in all our exploration borings. The fill encountered in our exploration borings generally consisted of very loose to medium dense, moist, brown, brownish orange, and olive, sand with highly variable amounts of silt, relatively lower amounts of gravel, and trace to some amounts of organics. The fill ranges in depth from approximately 9 feet below the existing ground surface in borings EB-1 and E13-2, to 3 to 5 feet in borings E13-3 and E13-4. We interpret the fill has moved during past landslide activity and thus have placed it under the "Quaternary Landslide Debris" heading on the boring logs. Quaternary Landslide Debris (Lodgement Till) Soils interpreted as lodgement till derived landslide debris were only observed in one exploration boring (EB-3) from 3 to 6 feet underlying the unit described above. These sediments July 1, 2022 ASSOCIATED EARTH SCIENCES,INC. SASlih-20180614EO01-002 Page 3