2325 TAYLOR DR Geotech Report 2022-10-25

• January 26th, 2018 G-4588 2325 Taylor Drive Page 2 exhibit firm and unyielding conditions in their native,undisturbed condition, but can become unstable and prone to landslides in steep slope areas due to jointing or high-water content. Geological maps2 also show Quaternary Whidbey formation deposits overlapping the northern end of the property. Whidbey formation generally comprises mostly cross-bedded sand,which is very compact, medium to coarse grained, and commonly oxidized. Slope Conditions: The north-facing steep slope described in the background section of this report was evaluated based on topography data sourced from both the"Boundary and Topographic Survey" developed by ALL Land Surveying(1/5/18) as well as Map of Everett online interactive map. The setback distance between the edge of the footprint of the existing house and the top of the slope varies between 100 to 150 feet. However,the footprints of both of the proposed developments are positioned farther away from the top of the slope than the footrprint of the existing house. The slope descends away from the house for a horizontal distance of approximately 150 feet and vertical distance of approximately 90 feet from top to toe. On average, the percent slope gradient measures about 80 to 90 percent, but measures 118 percent for slope gradient at its steepest point (the steepest point is about a 10 to 20 feet distance from the top of the slope). Geologic Hazard Classification: Geologic hazard classification of the steep slope on the subject property was applied based on EMC's criteria and standards in chapter 19.37.080. The following subsections present geological hazard classifications with explanations for the basis of each classification. Landslide Hazard: The slope is identified as a"very high/severe" landslide hazard as defined EMC chapter 19.37.080, because the slope gradient exceeds 15% and the sloped area is mapped as transitional beds (Qtb) and Whidbey formation (Qw). This classification is based on Dames and Moore Methodology for the Inventory, Classification and Designation of Geologically Hazardous Areas City of Everett, Washington:July 1, 1991,which City of Everett has adopted as an authority for evaluating slopes. Seismic Hazard: In terms of seismic risk classification,the project site is classified as having a very low susceptibility to liquefaction based on Liquefaction Susceptibility Map of Snohomish County developed by the Washington State Department of Natural Resources (2004). Consequently, the sloped area is not considered a seismic/liquefaction hazard per EMC chapter 19.37.080. Erosion Hazard: The slope is also defined as a high erosion hazard per EMC chapter 19.37.080, because it exceeds 40%in slope gradient. GEO Group Northwest,Inc.