1205 50TH ST SW 2020-07-02 - Laserfiche WebLink

NELSON GEOTECHNICAL ASSOCIATES, INC. GEOTECHNICAL ENGINEERS&GEOLOGISTS Main Office Engineering-Geology Branch 17311 135*Ave NE,A-500 5526 Industry Lane,#2 Woodinville,WA.98072 East Wenatchee,WA 98802 (425)486-1669•FAX(425)481-2510 (509)665-7696-FAX(509)665-7692 May8,2018 Mr.Ty Larsen 1205 50th Street SW Everett,Washington Geotechnical Engineering Evaluation Larsen Property Garage 1205—50th Street SW Everett,Washington. NGA Job No. 1033518 Dear Mr.Larsen: We are pleased to submit the attached report titled "Geotechnical Engineering Evaluation - Larsen Property Garage — 1205 - 50th Street SW — Everett, Washington." This report summarizes the existing surface and subsurface conditions within the site and provides general recommendations for the proposed site development. Our services were completed-in.,general accordance with the proposal signed by you on March 22,2018. The property is currently occupied by an existing single-family residence within the central portion of the property. The ground surface within the proposed development area and the overall property is gently to moderately sloping down from the southern property line along the access driveway to the northeast. An existing concrete rubble and short moderate slope are located along the upper eastern property line. The exiting concrete rubble wall appears to be supporting the backyard area of the neighboring property above and to the east of the subject property. We understand that the proposed development consists of constructing a new garage structure along the toe of the moderately sloping area within the eastern portion of the property immediately below the concrete rubble wall. We have been requested by you to provide a geotechnical evaluation of the proposed site development. We explored the proposed development area and the sloping portions of the site with five hand-tool excavations. Our explorations indicated that the proposed development area and sloping portions of the site are generally underlain by surficial undocumented fill soils with competent native glacial till soils at depth. It is our opinion that the planned garage is feasible from a geotechnical standpoint, provided that our recommendations are incorporated into the design and construction of this project. We have recommended that the new structure be founded on medium dense or better native glacial till soils for bearing capacity and settlement considerations. These soils should generally be encountered approximately three to four feet below the existing ground surface within the proposed building area, based on our explorations. It is also our opinion that the soils that underlie the site and form the core of the site slopes within the proposed development area should be stable with respect to deep-seated earth movements,due to their inherent strength and slope geometry. However,there is a potential for shallow sloughing and erosion events to occur on the steeper site slopes. We understand the proposed garage is to