2802 HOYT AVE EVERETT ELKS Geotech Report 2018-01-02 MF Import

Geotechnical Engineering Evaluation Everett Elks Club November 2, 200E NGA File No. 751106 Page 5 Erosion Hazard The erosion hazard criteria used for determination of affected areas includes soil type, slope gradient, vegetation cover, and groundwater conditions. The erosion sensitivity is related to vegetative cover and the specific surface soil types, which are related to the underlying geologic soil units. The Soil Survey, Snohomish County Area Washington, by the Soil Conservation Service (SCS) was reviewed to determine the erosion hazard of the on -site soils. The site surface soils were classified using the SCS classification system as Alderwood-Urban land complex, 2 to 8 percent slopes. Th:s unit is listed as having a slight erosion hazard. CONCLUSIONS AND RECOMMENDATIONS General It is our opinion, that from a gcotechnical standpoint, the site is compatible with the planned development. Our explorations around the perimeter of the site indicated that the site is generally underlain by competent glacial soils. However, significant fill may exist around the existing structure - Tile extent of such a condition should be evaluated during construction, and construction :methods adjusted as recommended by NGA to mitigate such potential. These native soils should provide adequate support for the planned foundations, slab -on -grade, and pavement loads. This is further discussed in the Foundations subsection of this report. The main geotechnical issue concerning development on this site is maintaining the stability of tlhe cuts planned for installing the underground parking garage. We anticipate that cuts up to to feet in height may be needed on the southern, eastern, and northern sides of the site to facilitate the planned structure. A commercial building is located on the neighboring property just to the south of the southern property line. Sidewalks are located adjacent to the building on the northern and eastern property lines. Based on these conditions, and if the recommended temporary cut inclinations can not be achieved, we recommend that the planned cuts be shored. It is our understanding that the existing retaining walls may be incorporated into the new building to eliminate the need for a new shoring wall. This should be evaluated by the structural engineer. If the existing walls cannot be incorporated into the design, the most practical system would be a soldier pile wall consisting of steel H-beams bridged with treated lumber or concrete panels. The shoring system can be temporary or can be made permanent and incorporated into the building design. This is further discussed in the Shoring Wall subsection of this report. NELSON GEOTECHNICAL ASSOCIATES,7i1TC.