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4702 W Glenhaven Dri��e CAO,Snohomish County,`�ashingron Mater•ials Testirig& Consulting,inc. <br /> JLl(v 3l. 2017 16B03U <br /> MTC's scope of work did not include determination of seasonal ground�uater elevation variations, <br /> documentation of wet season site conditions, or conclusive measurement of groundwater elevations at <br /> depths past the extent feasible for exploration. Stable regional groundwater level is assumed to be below <br /> the depth of concern for this study, based on topographic conditions and site elevation, and vicinity <br /> surface water occurrences in the subject area. <br /> Surrrmarv of Geolo�ic Literature Review: <br /> MTC reviewed available map publications to assess lknown geologic conditions and hazards present at <br /> the site location. The Washin��ton interactive Geologic Map, maintained by the Department of Natural <br /> Resources Division of Geolo�ry and Earth Resources (DNR DGER) depicts mapped surface geology of <br /> 1:24,000-scale detail. MTC reviewed available map publications and online literature sources to assess <br /> geologic conditions and slope stability present at the site location and vicinity. These available resources <br /> map the project site, in the vicinity of the existing residence, as Quaternary Vashon Till (Qvt), of the <br /> latest Vashon Stade. These soils commonly consist of silty sandy gravel mixtures, and can be densely <br /> compact to cemented below weathered and deleterious cover soils. Along the contour of the slope, a unit <br /> of Quaternary Vashon Advance Outwash (Qva) was mapped. These soils commonly consist of sandy <br /> gravel to medium and fine grained sands, and oaidize to shades of brown. Two small historic landslides <br /> are depicted along Pigeon Creek Number 2, approximately a quarter mile to the northeast, situated in fine <br /> grained alluvial deposits of silt and sand. <br /> The NRCS Web Soil Survey mapped the near-surface soils in the vicinity of the e�isting residence as <br /> Alderwood-Urban land complex, 8 to 15 percent slopes (6). This soil unit was described as a moderately <br /> deep deposit formed on till plains in glacial till. Typically the surface soil is found as very dark grayish <br /> brown gravelly sandy loam to about 7 inches below present grade (BPG), the subsoil consists of dark <br /> ye(lowish brown very gravelly sandy loam to about 30 inches BPG followed by olive brown very <br /> gravelly sandy loam to about 35 inches BPG, and the substratum is described as weakly cemented <br /> hardpan to depths in excess of 35 inches BPG. Strati�;raphy varies in this soil unit and the depth to the <br /> hardpan can be as little as 20 inches. Permeability is moderately rapid through the surface and subsurface <br /> soils and very slow through the hardpan layer. Runoff is slow with slight hazards of water erosion. Near- <br /> surface soils mapped to the north of the site followving the slope contour were Alderwood-Everett <br /> gravelly sandy loams, 25 to 70 percent slopes (4). This soil unit was described as a moderately� deep <br /> deposit formed on till plains, terraces, and outwash plains in glacial till. Typically the surface soil is <br /> found as very dark grayish brown gravelly sandy loam to about 7 inches BPG, the subsoil consists of <br /> dark yellowish brown and dark brown very gravelly sandy loam to about 30 inches BPG followed by <br /> olive brown very gravelly sandy loam to about 35 inches BPG, and the substratum is described as weakly <br /> a <br />