4704 HARBOR LN 2018-01-02 MF Import

Final Summary Letter Anderson Slope Stabilization Everett, Washington NGA File No. 816909 May 14, 2010 Page 2 properties previously mentioned. Evidence of settlement and subsidence was observed at the top of the slope and in the vicinity of the swimming pool. A few weeks prior to the landslide, large tress on the steep slope on your property and your neighbor's properties (Lots 48 and 49) were cut down; however, we determined that the primary cause of the landslide was the substantial water leakage from the irrigation system. It was our understanding that a portion of the residence, including foundation subgradcs, was damaged by the leaking water. We were not involved in this portion of the project and do not have knowledge of the current conditions of the effected portions of the residence or the subsequent repairs. After the landslide, the City of Fvcrett issued you a letter summarizing short- and long-term repair measures that they required be implemented. For the short temp, the City requested a plan for restoring the trees that had been removed, as well as for erosion control and maintenance, and a report from a geotechnical engineer regarding the stability of the slope. For the long term, the City indicated that the slope/critical area must be restorcd per wi approved restoration plan, with respect to City codes and regulations, and that the recommendations from a gootecluucal engineer should be followed, as approved by the City. SITE. EVALUATION AND SLIDE REPAIRS We conducted ,in extensive exploration program which included drilling several gcotechnical borings at the top of the slope and in front of the house, as well as mapping the slope, to dcictmine the extent of the landslide, and to develop a repair plan. We prepared a geotechnical report for the project titled "Geotechnical langincering rvaluation — Anderson Iandslidc Repair 4704 Harbor Lane — Evcrctt, Washington," dated September 15, 2009. Based on our explorations, si.c observations, and slope stability analyses, we determined that the core of the slope was stable. It was our opinion that permanent stabilization of the slide and prevention of fimher slope movement would require stabilizing the slope with a permanent soldier pile retaining wall with tie -backs. Below the proposed wall, slope restoration and re -vegetation were recommended to improve surficial stability of the slope. We also provided recommendations fir improving the overall drainage picture of the site. We provided specific icconunendations for designing and installing the recommended shoring system, and for improving One erosion and drainage conditions of the site and steep slope. NELSON GEOTECHNICAL ASSOCIATES, INC.