1907 W MUKILTEO BLVD 2021-11-15 - Laserfiche WebLink

' Pearson Property Slope Stabilization NGA File No 945216 1907 West Mukilteo Boulevard February 19,2016 Everett,Washington Page 2 SCOPE The purpose of this study is to explore and characterize the site subsurface conditions, and provide our opinions and recommendations regarding the existing slope stability and proposed stabilization measures. Specifically,our scope of services includes the following: 1. Review available soils and geologic maps of the area. 2. Explore the subsurface soil and groundwater conditions within the site with two up to 25 feet deep borings, using a limited-access track-mounted drill rig. The drill rig was subcontracted by NGA. 3. Map the conditions on the slope and evaluate current slope stability conditions and perform shallow hand explorations,as needed. 4. Provide recommendations for improving slope stability, including the use of light retaining structures, erosion control systems, and drainage improvements. 5. Provide recommendations for long term slope maintenance. 6. Document the results of our explorations, findings, conclusions, and recommendations in a written geotechnical report. SITE CONDITIONS Surface Conditions The site consists of an irregular-shaped parcel covering approximately 0.76 acres. The site is occupied by a 1 1/2-story, single-family residence with a partial daylight basement and a detached garage structure within the relatively level to gently sloping eastern portion of the site. A level lawn area is located to the north, south and west of the residence along the top of a steep west-facing slope. The residence is currently setback approximately 20 feet from the top of the steep slope while the existing deck along the northwest corner of the residence is setback approximately 15 feet from the top of the steep slope. The steep west-facing slope descends from the western yard area at an approximate gradient of 38 degrees(78 percent) to a gently to moderately sloping area located at the toe of the steep slope above the railroad tracks. A profile of the existing ground surface and the interpreted subsurface conditions are presented in Cross Sections A-A' in Figure 3. It appears that documented fill soils and yard waste have been placed within the yard and slope areas along the top of the steep slope. The steep slope is generally vegetated with grass,thick underbrush, and blackberries. We did not observe significant signs of deep-seated slope movement during our site visit. Some minor erosion and ground settlement were observed along the top of slope immediately below the yard area. We also did not observe surface water during our site visit on January 21, 2016. However, we did observe some significant groundwater seepage near the toe of the NELSON GEOTECHNICAL ASSOCIATES, INC.