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Geotechnical Engineering Evaluation NGA File No. 961916 Mason Residence Addition and Deck August 24,2016 Everett,Washington Page 3 ! 's 50 degrees (70 to 119 percent). The ground surface and interpreted subsurface conditions are shown on Cross Sections A-A' and B-B' in Figures 3 and 4, respectively. The site slopes are generally covered with underbrush, blackberries, and young to mature trees. We did not observe surface water on the site during our site visit on July 26, 2016. However, we did observe minor groundwater seepage emitting from the steep slope below the top of slope. We also observed numerous plastic drainpipes within the sloping area along the northeastern property line. We were unable to determine the exact extents of the drainlines during our site visit. We anticipate that some of these pipes may originate on the subject site and the neighboring property to the northeast. We also did not observe significant signs of recent slope movement within the site slopes below the residence. An old landslide scarp was observed within the steep slope area well to the north of the residence. Subsurface Conditions Geology: The geologic units for this area are shown on the Geologic Map of the Everett 7.5-Minute Quadrangle, Snohomish County, Washington, by James P. Minard (U.S.G.S., 1985). The site is mapped as Advance Outwash (Qva), Transitional Beds (Qtb) and Whidbey Formation (Qw). The advance outwash is described as clean, stratified sand and gravels. The transitional beds unit is described as a deposit of clay, silt, and very fine sand. The Whidbey formation deposits are described as medium- to coarse-grained sand. Our explorations generally encountered undocumented fill soils underlain by fine- to medium-grained sand with silt and gravel and silt with varying amounts of sand consistent with the description of Advance Outwash and transitional bed deposits,respectively. Explorations: The subsurface conditions within the site were explored on July 26, 2016 by drilling three borings to depths in the range 11.5 to 26.5 feet below the existing ground surface using a portable, limited-access drill rig. We also performed two hand hole explorations on the slopes below the residence, and proposed deck and addition area. The approximate locations of our explorations are shown on the Schematic Site Plan in Figure 2. A geologist from Nelson Geotechnical Associates, Inc. (NGA) was present during the explorations, examined the soils and geologic conditions encountered, obtained samples of the different soil types, and maintained logs of the explorations. A Standard Penetration Test (SPT) was performed on each of the samples during drilling to document soil density at depth. The SPT consists of driving a 2-inch outer- diameter, split-spoon sampler 18 inches using a 140-pound hammer falling 30 inches. The number of blows required to drive the sampler the final 12 inches is referred to as the "N"value and is presented on the boring logs. The N value is used to evaluate the strength and density of the deposit. NELSON GEOTECHNICAL ASSOCIATES, INC.