4704 HARBOR LN 2018-01-02 MF Import

[] NELSON GEOTECHNICAL ASSOCIATES, INC. GEOTECHNICAL ENGINEERS & GEOLOGISTS Main Office 17311 — 135" Avenue NE, A-500 Woodinville. WA 98072 (425) 486.1669 FAX (425) 481-2510 (425) 337-1669 Snohomish County September 15, 2009 Rick and holly Anderson 4704 .larbor lane Everett, Washington 98201 Gcotcchnical Engineering Evaluation Anderson Landslide Repairs 4704 Harbor Lane Everett, Washington NGA File No. 816909 Dear Mr. & Mrs. Anderson: Engineering -Geology Branch 437 East Penny Road Wenatchee, WA 98801 (509) 665.7696 FAX (509) 665.7692 We are pleased to submit the attached report titled "Gcotcchnical Engineering Evaluation - Anderson Landslide Repairs - 4704 Harbor Lane - Everett, Washington.- This report summarizes the existing surl'ace and subsurface conditions within the site and provides recommendations for the repair and stabilization of the site's tailing slopes. Our services were completed in general accordance with the proposal signed by ,lobo C. Dippold on August 28, 2009. The site is situated on gently to steeply norllomest-facing sloping ground above Merrill & Ring Creek. The site is currently occupied by a single-family residence with a daylight basement and an outdoor swimming pool. An area of the upper portion of the slope downslope from the residence recently experienced major slope movement. An exposed scarp has fornied directly below the top of the slope. We understand that a significant water leak occurred in front of the house shortly prior to of the observance of the landslide. We understand that some trees were removed from the slope a 11ew weeks prior to the slide. We monitored the drilling of five gcotechnical borings adjacent to the slope and in front of the residence, mapped the slope, and completed hand auger explorations on life slope. We also researched the site vicinity including if review of aerial photos and prior reports. Our explorations indicated that the area near the top of the slope consisted of loose soil and undocumented fill, with competent native glacial material encountered at depth. Based oil our observations and subsurface explorations, it is our opinion that the recent slope movement has affected a relatively localized area oil the slope directly below the residence. It is our opinion that the recent slide was directly related to the water leakage on the other side of the residence. It is our understanding that in the upwards of 250,000 gallons of water leaked out ofa broken irrigation line over a two-day period, just prior to the slide. We did not sec evidence that this water flowed over the slope. I lowever, during our initial visit to the site on .luly I, 2009 shortly after the slide, water was still flowing from the slope within life slide area roughly 15 feet below the top of the slope. The water leakage and the 2