4110 CLIFF DR 2022-01-26 - Laserfiche WebLink

Geotechnical Engineering Evaluation NGA File No. 1021318 Cliff Drive Short Plat Residence Development February 2, 2018 Everett, Washington Page 2 12. Provide recommendations for site drainage and erosion control. 13. Document the results of our findings, conclusions, and recommendations in a written geotechnical report. SITE CONDITIONS Surface Conditions The site consists of an irreular-shaped parcel covering approximately 0.38 acres. The lot is currently occupied by a single-family residence with a daylight basement along the upper eastern side of the property. The remaining portions of the property are vegetated with grass, sparse young to mature trees, and landscaping plants. The ground surface within the properties slopes gently to moderately down from the eastern property line along Cliff Drive to the western property line at gradients in the range of approximately 7 to 14 degrees (12 to 25 percent) as shown on Cross Section A -A' in Figure 3. The ground surface continues to slope gently to the west outside of the property to a ravine area within Howarth Park. The site is bounded to the north and south by existing residential properties, to the east by Cliff Drive, and to the west by Olympic Boulevard. We did not observe surface water or seepage emitting from the site slopes within the site during our visit on January 10, 2018. We also did not observe any indications of recent slope movement within the property during our site visit. Subsurface Conditions Geology: The geologic units for this area are shown on Geologic map of the Everett 7.5 minute quadrangle, Snohomish County, Washington, by Minard, J.P. (USGS, 1985). The site is mapped as advanced outwash (Qva). Advanced outwash is described as clean, mostly gray, well -stratified, unconsolidated sand with pebbles, and some cobbles. Our explorations typically encountered undocumented fill/topsoil underlain by competent gray -brown, fine to medium sand with silt and trace amounts of gravel, consistent with the description of advanced outwash. Explorations: The subsurface conditions within the properties were explored on January 10, 2018 by monitoring the excavation of four test pits to approximate depths in the range of 7.0 to 10.0 feet below the existing ground surface. The approximate locations of our explorations are shown on the Schematic Site Plan in Figure 2. A geologist 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. The soils were visually classified in general accordance with the Unified Soil Classification System, presented in Figure 4. The logs of our test pits are attached to this report and are presented as Figure 5. We present a brief summary of the subsurface conditions in the following paragraphs. For a detailed description of the subsurface conditions, the test pit logs should be reviewed. NELSON GEOTECHNICAL ASSOCIATES, INC.