4704 HARBOR LN 2018-01-02 MF Import

• Geotechnical Engineering Evaluation Anderson Landslide Repairs 4704 I larbor Lane I Everett, Washington September 15, 2009 I NGA Pile No. 816909 Page 4 undennined by the slide. It appears that the black corrugated pipe that is exposed on the slope at one time was connected to this solid black pipe at a •,,r". The solid pipe has duct tape on the "T" where the corrugated pipe was probably connected. Subsurface Conditions Geology: The geologic units for this area are shown on the Distribution and Description of Geologic Units in the Mukilteo Quadrangle Snohomish County, Washington, by James I'. Minard (U.S.G.S., 1982). The site is mapped as Transitional Beds (Qtb). The Transitional Beds unit is described as thick beds of gray clay, sill, and line- to very -fine sand. Our explorations encountered glacial deposites underlain by the Transitional Beds. Undocumented fill lies along the top of slope across this area. We have noted that rill had been placed along the northwest portion of the upper slope to construct the pool and Jacuzzi. Wood Walls terraced Idown the slope also exist to the west of the pool that appears to support fill. We reviewed the Coastal Zone Atlas of Washington (WSDOE, 1978) for geologic and stability conditions within the site and surrounding area. The site is mapped as being underlain by Non -Glacial Sediments (Qns), consisting of glacial and non -glacial deposits, with Glacial 'fill (Qvt) overlying adjacent to and just upslope of this location. The glacial till generally consists of dense, silty sand within gravel, derived from deposition by the latest continental glacial activity within the area. The underlying fine-grained Qns stratum can include lake deposits from advancing and retreating glacial periods. The site is located within the area described as "unstable" (U) within the Qns deposits, near the "stable" (S) areas of Qvt. 'rbe Geologic Map of Washington — Northwest Quadrant, by Joe D. Dragovich, et. at. (WSDNR, 2002) was also referred for the general geologic conditions at the site and for our aerial interpretations. The site area is mapped as glacial till (Qgt) and advance outwash (Qga), with similar descriptions and derivations. However, Within the Merrill & Ring Creek ravine areas to the north and west of the site, deposits described as Pleistocene Continental Sediments (Qc) are identified. These materials are described as being composed of stratified clay, silt, sand, and gravel of fluvial, deltaic, lacustrine, and estuarine origins, including part of the non -glacial Whidbey Ponnation. NELSON GEOTECHNICAL ASSOCIATES, INC. 10