1329 MADRONA AVE Geotech Report 2022-10-25

Subsurface Exploration,Geologic Hazard,and Janowicz Property Geotechnica!Engineering Report Everett,Washington Project and Site Conditions silt with trace gravel was encountered to a depth of 17%feet in exploration boring EB-2. These deposits are interpreted as colluvium. Colluvium is surficial soil that has moved downslope under the forces of gravity and can be associated with shallow landsliding. The low density, high silt content, and variability of this material render it unsuitable for direct support of foundations for the structure. Landslide Deposits Medium dense to dense,wet, gray,very silty fine sand interpreted as landslide deposits were encountered from 17% to 28 feet below the ground surface in exploration boring EB-1. The colluvium encountered in EB-2 may also be interpreted as landslide deposits. Landslide deposits typically consist of intermixed soils from nearby units transported downslope under forces of gravity, possibly facilitated by groundwater flowing laterally over a low-permeability underlying stratum. The random nature of deposition and potentially high variability in consistency and density of these deposits make them unsuitable for direct support of foundations for the structure. Pre-Vashon Non-Glacial Sediments Both exploratory borings were terminated in dense to very dense and hard, moist to wet, gray, very sandy silt and very silty fine sand with trace gravel and occasional organics interpreted as pre-Vashon non-glacial sediments. This deposit was encountered at a depth of 28 feet in EB-1 and 17%feet in EB-2. A thin layer at the top of this deposit in EB-1 was gravelly. These soils were deposited by still or slowly moving water before the advance of the Vashon Stade. 4.2 Geologic Literature Our interpretations of subsurface conditions onsite generally agree with the conditions shown on a published geologic map of the area. We reviewed the Geologic Map of the Everett 7.5' Quadrangle, Snohomish County, Washington, by J.P. Minard, 1985. The referenced map indicates that the site is underlain by transitional beds, which were deposited before the Vashon Stade of the Fraser Glaciation. The landslide deposits on our site are not mapped; however, the map delineates a limited number of landslides and directs the reader to additional resources. The Washington State Department of Ecology (Ecology) Washington State Coastal Atlas identifies the uphill half of the property as unstable slope. This designation reflects the colluvium and landslide deposits encountered during our subsurface exploration. May 10,2018 ASSOCIATED EARTH SCIENCES,INC NSAd-170549E002-2-Prolects120170S491KEW Page 4