909 51ST PL SW Geotech Report 2022-10-25

1 Geotechncial Engineering Evaluation Garcia Property Additions Everett, Washington SCOPE NGA Project No. 1040218 June 22, 2018 Page 2 The purpose of this study is to explore and characterize the subsurface conditions within the site and to provide opinions and recommendations for the development of the proposed additions. Specifically, our scope of services included the following: 1. A review of available soil and geologic maps of the area. 2. Exploring the site subsurface conditions using hand -auger tools. 3. Mapping the conditions on the slope, performing shallow hand -tool excavations, cross - sections, and evaluating current slope stability conditions. 4. Performing grain -size sieve analysis on soil samples, as necessary. 5. Providing our opinions regarding the site slope conditions. 6. Providing recommendations for building setbacks from the steep slope. 7. Providing recommendations for earthwork and foundation support. 8. Providing recommendations for temporary and permanent slopes. 9. Providing recommendations for slab and pavement subgrade preparation. 10. Providing recommendations for site drainage and erosion control. 11. Documenting the results of our findings, conclusions, and recommendations in a written geotechnical letter. SITE CONDITIONS Surface Conditions The site consists of a roughly triangular -shaped parcel covering approximately 0.31 acres. the site is currently occupied by an existing single-family residence within the southwestern portion of the property. The parcel is bordered to the northwest and south by existing residential development, accessed within the property from the southwest by the 51" Place SW cul-de-sac. The ground surface within the proposed development area is relatively level to gently sloping; however, the top of a steep ravine slope associated with Pigeon Creek No. 2 occupies the vicinity of the eastern property line and extends into the adjacent, undeveloped property to the west. At the top of the ravine slopes, concrete block retaining walls are retaining up to 3.0 feet of soil at the top of the slope to level the backyard. Ravine slopes step down to the northeast at gradients of up to 33 degrees (65 percent grade), as shown on Cross Section A -A' in Figure 2. While we noted the presence of anthropogenic debris, including construction litter and lawn clippings on the steep ravine slopes, we did not observe any surface water during our site visit on May 24, 2018. NELSON GEOTECHNICAL ASSOCIATES, INC.