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Kierstein Residence Retaining Wall <br />Everett, Washington Geotechnical Engineering Report <br />generally consisted of loose to medium dense, iron oxide stained, moist, olive, silty sand with <br />trace amounts of gravel. We interpret this to be a small block of lodgement till that has moved <br />during past landslide activity and thus have placed it under the "Quaternary Landslide Debris" <br />heading on the boring logs. <br />Quaternary Landslide Debris (Advance Outwash) <br />Soils interpreted as advance outwash derived landslide debris were encountered in exploration <br />borings EB-2 through EB-4 underlying the units described above. These sediments generally <br />consisted of very loose to medium dense, iron oxide stained, moist, brownish orange to olive, <br />sand with trace to some amounts of silt and trace amounts of gravel. We interpret this to be <br />weathered advance outwash that has moved during past landslide activity and thus have placed <br />it under the "Quaternary Landslide Debris" heading on the boring logs. <br />Vashon Advance Outwash <br />Below the units described above in all four of our exploration borings, we typically encountered <br />medium dense to very dense, moist, light olive to brownish olive, fine sand ranging to fine to <br />coarse sand with trace to some amounts of silt, and trace amounts of fine gravel, interpreted as <br />Vashon-age advance outwash. Advance outwash was deposited in rivers and streams ahead of <br />the southward advancing Vashon-age glacier around 15,000 years ago. <br />Hydrology <br />Groundwater was encountered in only one of four our borings (EB-2) at a depth of <br />approximately 16.5 feet at the time of drilling (April 2019). Based on the lack of observed <br />groundwater in boring EB-3 located downslope of EB-2, and the lack of observed emergent <br />groundwater seepage from the slope below the area of the walls, we interpret the observed <br />groundwater to be locally perched. Perched groundwater may occur within the sediments <br />encountered at the site during the winter and spring months. Perched ground water occurs <br />when surface water infiltrates down through relatively permeable soils, such as the fill or the <br />weathered portions of the glacial deposits, and becomes trapped or "perched" atop a <br />comparatively impermeable barrier, such as a silt interbed of siltier interbeds within the glacial <br />soils. This infiltration can occur at great distances from the area where the groundwater is <br />encountered. It should be noted that fluctuations in the level of the ground water may occur <br />due to the time of year and variations in the amount of rainfall. The quantity and duration of <br />flow from excavations made into the perched zone will vary depending on season, topography, <br />and soil grain size. <br />�_1►L7►�iI111[cl_AlM►I <br />The western sloping portion of the site is classified as a high landslide hazards critical area <br />according to City of Everett Critical Areas Code Section 19.37.080. The site is characterized by a <br />relatively flat topography with a steep slope area along the west side of the site underlain by <br />loose to medium dense existing fill and native glacial soils. Based on the topographic survey <br />July 1, 2022 ASSOCIATED EARTH SCIENCES, INC. <br />SASlih - 20180614EO01-002 Page 4 <br />