2702 59TH ST SW 2024-07-05 - Laserfiche WebLink

Geotechnical Engineering Evaluation Miller Property Slope Stabilization 2702 — 59t" Street SW Everett, Washington INTRODUCTION This report presents the results of our geotechnical engineering investigation and evaluation of the landslide activity within and in the nearby vicinity of the Miller residence located at 2702 — 59t" Street SW in Everett, Washington, as shown on the Vicinity Map in Figure 1. The Snohomish County Parcel number for the subject property is 008027-000-015-00. The purpose of this study is to explore and characterize the site's surface and subsurface conditions, and to provide geotechnical recommendations for site stabilization. The subject site is known as Lot 15 of the Powder Mill Highlands residential development. Topographically, the site is situated on a relatively level to gently sloping bench with moderate to steep south -facing ravine slopes below and to the south of the property, which is primarily contained on City of Everett -owned property and provides approximately 80- to 90-feet of vertical relief. The recent slide activity caused up to approximately 6- to 10-feet of overall vertical offset between the areas immediately south of the Miller residence to the top of slope. The affected area spans nearly the entire width of the Miller property and the southeastern to south-central portion of the neighboring parcel to the west. The existing site layout is shown on the Schematic Site Plan in Figure 2. 441610 The purpose of this study is to explore and characterize the site surface and subsurface conditions and provide recommendations for mitigation and stabilization of landslide hazards. Specifically, our scope of services included the following: 1. Reviewing available soil and geologic maps of the area as well as other relevant geotechnical information, as provided. 2. Exploring the subsurface soil and groundwater conditions within the areas of the ground movement on the subject property with two drilled borings approximately 40 feet each in depth, using a limited -access drill rig. Drill rig was subcontracted by NGA. 3. Installing an inclinometer casing in one of the explorations on the property for long-term slope monitoring. 4. Mapping the conditions of the slide and ravine areas, perform shallow, hand -tool excavations, prepare cross -sections, and qualitatively evaluate current stability conditions. NELSON GEOTECHNICAL ASSOCIATES, INC.