10721 19TH AVE SE Geotech Report 2023-04-07

NELSON GEOTECHNICAL NGA ASSOCIATES, INC. GEOTECHNICAL ENGINEERS&GEOLOGISTS Main Office Engineering-Geology Branch 1731 I-135th Ave NE,A-500 5526 industry Lane,in Woodinville,WA 98072 East Wenatchee,WA 98802 (425)486-1669'FAX(425)481-2510 (509)665-7696•FAX(509)665-7692 November 9,2017 Ross Jameson 2812 Architecture ross@2812architecture.com Geotechnical Engineering Evaluation Zerzura Townhome Development 10725—19t"Avenue SE Everett,Washington NGA Job No. 1014317 Dear Mr.Jameson: We are pleased to submit the attached report titled "Geotechnical Engineering Evaluation — Zerzura Townhome Development — 10725 - 19th Avenue SE — Everett, Washington." This report summarizes the existing surface and subsurface conditions within the site and provides general recommendations for the proposed site improvements. Our services were completed in general accordance with our proposal signed by you on November 2,2017. The property consists of a rectangular-shaped parcel covering approximately 0.4-acres. The ground surface within the property is generally level and is currently occupied by a single-family residence and detached garage structure within the western and eastern portion of the site, respectively. We understand that the proposed development plans within the site will include removing the existing structures and constructing four,three-unit townhomes throughout the site. Specific grading and stormwater plans were not available at the time this report was prepared. However, we understand that stormwater generated within this site may be directed to on-site infiltration systems, if feasible. We explored the subsurface soil and groundwater conditions on October 19, 2017 with three trackhoe- excavated test pits, and one small-scale pilot infiltration test (PIT). In general, the test pits encountered medium dense to very dense silty fine to medium sand with gravel that we interpreted as native glacial till soils to the depths explored. It is our opinion that the proposed site development is feasible from a geotechnical engineering standpoint, provided that our recommendations for site development are incorporated into project plans. In general,the native glacial till soils underlying the site should adequately support the planned structures. Foundations should be advanced through any loose soils down to the competent glacial material interpreted to underlie the site, for bearing capacity and settlement considerations. These soils should generally be encountered approximately two to three feet below the existing ground surface,based on our explorations. If undocumented fill is encountered in unexplored areas of the site, it should be removed and replaced with structural fill for foundation and pavement support.