1907 W MUKILTEO BLVD 2021-11-15 - Laserfiche WebLink

• Pearson Property Slope Stabilization NGA File No 945216 1907 West Mukilteo Boulevard February 19,2016 Everett,Washington Page 3 12 steep slope. Due to the dense vegetation along the surface of the steep slope we were unable to observe where the groundwater seepage was emitting from the slope area. The property is bordered to the north by the Burlington Northern and Santa Fe Railway railroad tracks and Puget Sound, to the east and west by residential properties, and to the south by West Mukilteo Boulevard. The site layout within the vicinity of the residence is shown on the Schematic Site Plan in Figure 2. We observed that drainage associated with the roof drains around the residence appear to be directed to underground pipes. We were unable to delineate where these pipes were being directed to. However, we were informed by the homeowner that there may be a pipe that tightlines the drains downslope. We were also not able to find this drain pipe during our site visit. 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 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: The subsurface conditions within the site were explored on January 21, 2016 by drilling two borings to depths in the range 25.3 to 31.5 feet below the existing ground surface using a limited- access tracked drill rig. 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.