1901 W MUKILTEO BLVD Geotech Report 2022-10-25

Scriven Residence Improvements-REVISED NGA File No 974316 1901 West Mukilteo Boulevard November 29,2016 Everett,Washington Page 4 Subsurface Conditions Geology: The geologic units for this area are shown on the Distribution and Description of Geologic Units, Mukilteo Quadrangle, Washington, by James P. Minard (U.S.G.S., 1982). The site is mapped as Transitional Beds (Qtb) with Advance Outwash (Qva) mapped nearby. The Qtb is described as thick beds of clay, silt, and fine sand. The Qva is described as mostly clean,pebbly sand. Our explorations and the previous exploration performed by others generally encountered loose surficial material underlain by fine to medium sand with varying amounts of silt and gravel consistent with the description of advance outwash deposits. Explorations: We visited the site on October 24, 2016 to explore the subsurface conditions within the proposed development areas and the steep slopes with hand hole explorations. The approximate locations of our explorations are shown on the 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, and maintained logs of the explorations. The soils were visually classified in general accordance with the Unified Soil Classification System, presented in Figure 4. The logs of our explorations are presented as Figures 5 and 6. The following paragraph contains a brief description of the subsurface conditions encountered in the explorations. For a detailed description of the subsurface conditions,the hand auger logs should be reviewed. In all of our hand hole explorations, we encountered approximately 0.1 to 1.0 of surficial grass and topsoil. Underlying the surficial soils in all of our hand augers,we encountered approximately 2.4 to 5.0 feet of loose to medium dense, dark brown to brown silty fine to medium sand with gravel, and varying amounts of organic debris that we interpreted as undocumented fill soils. Below the undocumented fill in Hand Augers 1 through 5,we encountered medium dense to dense, light brown fine to medium sand with varying amounts of silt and gravel that we interpreted as native advance outwash soils. Hand Augers 1 through 5 were terminated within the native advance outwash soils at depths in the range of 5.0 to 8.0 feet below the existing ground surface, while Hand Auger 6 met refusal in the undocumented fill soils at approximately 2.5 feet below the existing ground surface. We also reviewed the previously performed drilled borings by Geotech Consultants, Inc. It appears that two drilled borings were performed along the top of slope area within the site. In general, these borings encountered loose to dense, light brown to brown sand with varying amounts of silt and gravel to approximate depths in the range of 36.5 to 41.5 feet below the existing ground surface. NELSON GEOTECHNICAL ASSOCIATES, INC.