4735 GLENHAVEN DR Geotech Report 2022-10-25

• Geotechnical Engineering Evaluation NGA File No. 1113119 Dutton Foundation Stabilization and Slope Evaluation July 3,2019 Everett,Washington Page 2 �A 1. Review available soil and geologic maps of the area. 2. Map the conditions on the slope, and evaluate current slope stability conditions. 3. Perform shallow hand explorations on the slope and in the vicinity of the settling structure. 4. Perform laboratory testing on soil samples,as needed. 5. Provide recommendations for foundation underpinning, addressing IBC codes 1803.5.5 and 1803.6, as heeded. 6. Provide recommendations for drainage and erosion control improvements, as needed. 7. Document the results of our findings, conclusions, and recommendations in a written letter. SITE CONDITIONS Surface Conditions We visited the site on June 13, 2019 to observe the existing site conditions. The subject site consists of a trapezium-shaped parcel covering approximately 0.28 acres. The site is currently occupied by a single- family residence within the northwest-central portion of the site, with a newer family room addition towards the ravine side. The topography within the site gently slopes from northwest to the southeast within the northwestern portion of the property, with a moderate to steep southeast-facing ravine slope occupied by Pigeon Creek below the existing residence within the southeastern portion of the property. On the exterior of the residence, we observed a separation of the addition from the main portion of the home several inches wide,as well as exterior foundation distress on the addition. Based on conversations with you, we understand that the main house has a basement foundation, but the addition does not. We did not observe any standing or flowing water within the property during our site visit. The site layout is shown on the Schematic Site Plan in Figure 2. Subsurface Conditions Geology: The geologic units for this site are shown on The Geologic Map of the Everett 7.5 Minute Quadrangle, Snohomish County, Washington,by James P. Minard(USGS, 1985). The site is mapped as Qva (Vashon Glacial Advance Outwash Deposits) with small amounts of Qvt (Vashon Glacial Till Deposits) to the westernmost portion of the site. The Qva is described as a mostly gray stratified unconsolidated sand with pebbles, cobbles. It is locally silty and oxidized to shades of brown. Qvt described as a compact diamict of silt, sand and subrounded to well-rounded gravel, deposited under ice sheets generally found in a very dense condition. The soils generally encountered in our explorations consisted of a thick layer of uncompacted silty surficial fill soil and topsoil underlain by silty fine to medium sand and gravel consistent with the description of the native glacial deposits at depth. NELSON GEOTECHNICAL ASSOCIATES, INC.