215 DORN AVE Geotech Report 2022-10-25

Geotechnical Engineering Evaluation NGA File No. 1031018 Multi-Family Residential Development April 19,2018 Everett,Washington Page 2 8. Providing recommendations for slab and pavement subgrade preparation. 9. Providing recommendations for site drainage and erosion control. 10. Documenting the results of our findings, conclusions, and recommendations in a written geotechnical report. SITE CONDITIONS Surface Conditions The site consists of a rectangular parcel covering approximately 0.3 acres. The site topography is composed of relatively level to gently sloping ground. Currently, the property is vacant, besides a detached shed structure on the southeastern property line.The property appears to have been graded and was previously occupied by a residential-type structure and playground area prior to 2014. The site is bordered to the northwest, northeast, and southeast by existing moderately to densely spaced multifamily residential development, and to the southwest by Dorn Avenue.Vegetation on the property consists of very sparsely distributed young trees, grasses, weeds, and groundcover throughout the property. Surficial areas within the site contain mixed construction debris and litter. We did not observe surface water during our site visit on March 23,2018. Subsurface Conditions Geology: The geologic units for this area are shown in the Geologic map of the Everett 7.5-minute • Quadrangle, Snohomish County, Washington,by James P.Minard (USGS 1985). The site is mapped as glacial till(Qvt).The till is described as a non-sorted clay,silt,sand,pebbles,cobbles,and boulders. Our explorations generally encountered a suthcial layer of topsoil and/or undocumented fill underlain by a layer dense,silty,fine to medium sand with gravel,consistent with the description of glacial till at depth. Explorations: The subsurface conditions within the site were explored on March 23,2018 by excavating three test pits and two small-scale infiltration pits to depths ranging from 2.5 to 7.3 feet below the existing ground surface using a miniature,track-mounted backhoe. We conducted on-site infiltration testing within Infiltration Pit One and Infiltration Pit Two on the same day. The approximate locations of our explorations are shown on the 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 3. The logs of our test pits are attached to this report and are presented as Figures 4 and 5. We present a brief summary of the subsurface conditions in the following paragraph. For a detailed description of the subsurface conditions,the test pit logs should be reviewed. NELSON GEOTECHNICAL ASSOCIATES, INC. 85