1903 W MUKILTEO BLVD Geotech Report 2022-10-25

v ) GEOTECHNICAL ENGINEERING STUDY Slope Stability and Potential Stabilization Measures Li Property 1903 West Mukilteo Boulevard Everett, Washington This report presents the findings and recommendations of our geotechnical engineering study for the property at 1903 West Mukilteo Boulevard in Everett. We understand that you wish to have an analysis of the slide potential on the steep north slope completed. As a part of this, measures to improve stability and provide long-term protection of the yard and house were to be considered. SITE CONDITIONS SURFACE The Vicinity Map, Plate 1, illustrates the general location of the site in south Everett. The area of study for this project included the two adjoining properties located at 1901 (Scriven property) and 1903 (Li property) West Mukilteo Boulevard, This report is specific to the property 1903 West Mukilteo Boulevard. The subject site is located along the northern side of the West Mukilteo Boulevard, overlooking Possesion Sound and the Port of Everett. Immediately east of the subject property is the similarly-sized Scriven property (#1903), which is currently developed with a single- family residence. To the east of the Scriven property is an undeveloped property currently owned by Burlington Northern/Santa Fe (BNSF) railroad. The northern limits of the Li property extend down the steep northern slope to the existing railroad tracks along the Possession Sound to the north. This lot is also currently developed with a single family residence consisting of a two-story residence with an attached garage on the southwestern corner. The house appears to have a partial basement beneath, with a finished floor elevation of around 3 to 4 feet lower than the surrounding ground surface. The ground surface surrounding both homes is relatively level to gently sloping. However, the Li property is higher than the Scriven lot, and a 4-foot-tall concrete wall located off the northwest corner of the Scriven house separates the grade difference between the rear portions of the properties. To the north of the existing homes a large, steep slope drops down to the Puget Sound. This slope is approximately 80 feet tall and is steeply sloped. The Li residence is set back approximately 25 to 30 feet from the top of the steep slope. The top of the steep slope is very near the northern edge of the existing retaining wall on the shared property line, where some erosion or shallow soil raveling has caused the top of the slope to recede to within approximately 15 feet of the northwestern corner of the Scriven residence. Evidence of surface erosion was observed in this area, where the far northern portion of the footing for this wall has been undermined. There has obviously been some fill and unengineered landscape walls placed near the top of the steep slope in the past. This fill appears to be settling and may actually be shifting downslope. During our visit to the property, we were able to observe the conditions on the north slope from both the top and bottom. The slope is heavily overgrown and no signs of recent large-scale slope movement were visible. However, it Is apparent that there have been at least shallow "skin" slides on the steep slope in the past. This is a relatively common occurrence along this section of the north-facing slope. The toe of the slope is protected from wave attack by the BNSF railroad bed. GEOTECH CONSULTANTS,INC.