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Geotechnical Engineering Evaluation Miller Property Slope Stabilization Everett, Washington NGA File No. 1333322 July 1, 2022 Page 3 Slopes: Regional topography predominantly slopes westward into Powder Mill Gulch, while locally, the ground surface within the site is generally level to gently sloping towards steep south -facing ravine slopes along the southern edge of the property. The steep slopes generally descend from the southern portion of the property at gradients in the range of approximately 15 to 35 degrees (26.8 to 70.0 percent) down to the base of the unnamed, east -west trending gully, as shown on Cross -Sections A, B, and C on Figures 3 through 5. The overall vertical relief of the steep slopes below and to the south of the Miller residence is approximately 80- to 90-feet. Landslide Deformation and Slope Observations: Our involvement with the project began on January 14, 2022, when we were asked to visit the site after initial observations of potential instability were noted by the property owner. Upon arrival, we observed a roughly 220-foot-long scarp with a vertical offset of approximately 3- to 8-feet at the crown of the slide and as close as approximately 5- to 6-feet from the southeastern portion of the Miller residence. A complex of internal scarps and tension cracks were observed along the body of the landslide with indications of compression and extensional forces along the sharp hummocky terrain. The playset area within the southwestern portion of the Miller property appeared to be downset approximately 5- to 6-feet from previous elevation and similarly, a shed structure within the southeast corner of the adjacent residence to the west was entirely demolished and downset. The upper headscarp generally revealed undocumented fills soils with varying organic debris and several unidentified drains and irrigation lines. On February 28 and March 1, 2022, we returned to complete slope mapping to capture the morphology of the slope and landslide affected areas. Slope mapping consisted of 4 shallow hand auger explorations and three representative cross sections within the landslide body and slope below. We delineated the looser fill soils mantling the top of slope, and mapped locations of groundwater seepage on the face of the slope, where present. Vegetation across the site slopes predominantly consisted of mature alders, few coniferous trees, and a moderate understory of blackberries and other underbrush. The overall health of the trees along the slope was considered poor and observed numerous dead, downed or leaning trees. Localized groundwater seepage was observed across the steep ravine slopes. Additionally, pools of surface water were observed collecting along the upslope portion of the root wad for each downed tree. We also noted, a particular area along the upper portion of the slope and to the southeast of the property containing saturated mucky surface soils and abundant phreatophyte type vegetation. The most prominent surface expression of slide activity was constrained to the southern portion of the subject property, however further downslope we observed localized shallow erosional sloughing and skin slides. NELSON GEOTECHNICAL ASSOCIATES, INC.