1915 W MUKILTEO BLVD 2018-01-02 MF Import

Geotechnical Engineering Evaluation and Slide Repairs 1915 Mukilteo Boulevard July 26, 2006 NGA File No. 743206 Page 3 observed near the top of the slope. The concrete supports for the fence surrounding the backyard were exposed in several areas and slide debris was noted below the near vertical exposed face near the top of the northe!:a slope. This face was about 10 feet tall and exposed sand with silt material. 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). This unit is described as thick beds of clay, silt, and fine sand. Our explorations generally encountered loose s irficial material underlain by sand and silty sand deposits consistent with the description of Transitional Beds. Explorations: The subsurface conditions in the areas located directly above the top of the slope were explored on July 20, 2006 by drilling two borings to depths ranging from 30.4 to 30.5 feet below the existing surface using a portable drill rig. Hand auger explorations were completed on the slope during slope mapping at the site on July 23, 2006. The approximate locations of our explorations are shown on the Site Plan in Figure 2. An engineer from 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 I8 inches using a 140-pound hammer with a drop of 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 rtrength and density of the deposit. The soils were visually classified in general accordance with the Unified Soil Classification System, presented in Figure 6. The logs of our borings are attached to this report and are presented as Figures 7 and S. The logs of our hand tool explorations are attached to this report and are presented as Figure 9. We present a brief summary of the subsurface conditions in the following paragraphs. For a detailed description of the subsurface conditions, the boring logs should be reviewed. NELSON GEOTECHNICAL ASSOCIATES, INC. _ d