4704 HARBOR LN 2018-01-02 MF Import

• Geotechnical Engineering Evaluation Anderson Landslide Repairs 4704 Harbor lane Everett, Washington September 15, 2009 NGA Pile No. 816909 Page 3 The steep slope is approximately 100 to 120 lect in height and has an overall inclination of approximately 30 to 40 degrees (58 to 84 percent) down to the north, as shown on Cross -Sections A -A', B-B', and C-C' in Figures 3, 4, and 5 respectively. The slope is generally vegetated with alders, blackberry bushes, underbrush, and several mature trees. Many of the large trees on the slope have been recently cut down, and the debris is lying on the slope. The landslide occurred within the upper portion of the slope just to the west of the jacuzzi and pool. A steep, 20- to 30- foot wide landslide scarp face approximately 70 feet in length is situated directly below the top of the slope in this area. Landslide debris extends approximately 100 to 125 feet down the slope below the exposed scarp. Based on our observations, landslide debris did not flow directly into Merrill K Ring Creek. The soils exposed in the upper portion of the slope appeared to be sand with silt and gravel underlain by a thick sequence of silt and sand. Approximate locations of the landslide and debris areas are shown on the Slide Area and Wall Location Site Plan in Figure 6. Evidence of an older landslide was observed to the west of the current landslide. A vertical scarp is exposed at the top of' slope and a large slump is located below the scarp. We also observed somewhat recent minor slope failures within the middle portion of the slope immediately to the east and west of the recent landslide and on the neighboring property to the cast of the Anderson property. These failures appeared to be concentrated in the upper portion of the slope within the sand observed within the upper slope. These slope failures appear to be surf icial in nature. We observed seepage from the recent landslide, approximately 15 to 20 feet down from the top of slope during our initial visit to the site on July I, 2009. We observed more significant and constant seepage on the slope approximately 50 feet down from the top of slope during our most recent visit on August 26, 2009. A drain pipe embedded in washed rock and covered with filter fabric was encountered approximately two to three feel below the surface directly above the recent slide; its use is unknown. Fill and yard debris were observed cast over the lop of slope on the western side of the property. Black corrugated drain pipes were observed on the western side of the concrete walkway adjacent to the +ool, along the northern side of the concrete walkway adjacent to the pool, and also coming out of the slope approximately 15 feet below the top of slope. A solid 6- to 8-inch HIVE pipe is located within the slide area and has been NELSON GEOTECHNICAL ASSOCIATES, INC. 9