4816 HARBOR LN 2016-01-01 MF Import

Letter to Joe Johnston Project No. 9463-001 July 29, 2008 Page 2 north. This corner of the house is the area of the lowest ground surface etevation around the house. The ground surface rises along the west side of the house toward the southwest corner. There is a geritler sloping area that extends progressively further westward from the west side of the house as you move irorn the north to the south property line. The subject decks that are proposed to be replaced are located near the northwest and southwest corners of the house. The deck near the northwest corner is located on the north side of the house and extends eastward from the west side. The southwest corner deck is located on the west side and extends northward from the south side. The geologic mapping of the area, "Preliminary Surficial Geologic Map of the Mukilteo and Everett Qiiadrangles, Snohomish County, Washington°, by Mackey Smith, 1976, indicates that the upland in the area of the subject house is underlain by Vashon age glacial tiil, whereas much of the Merrill and Ring Creek valley slopes are composed of the underlying Whidbey Formation intergiacial sands and clayey silts. OBSERVATIONS My observations and opinions were primarily related to slope stability risk considerations related to the propossd deck replacements. I have been involved in a number of geotechnical studies in this part of Everett, between Pigeon Creek No.1 and Powder Mill Gulch, and am familiar with the instability of the various creek slopes. Many of these creek valley's are composed of soils as indicated in the abov� described geologic mapping. In my previous walking of these valleys, my observations indicated meta-stable slope conditions. There were predominately shallow slumps and kneeing of trees indicating siope creep behavior. However, these features were generally limited in size and appeared to be controlled somewhat by localized activities. These failures were observed to be fairly shallow, such that the expression at the top of the slope is likely to be limited to a distance on the order of 3 to 5 feet. Although the frequency of these shallow landslide is variable, their frequency can be limited by storm water runoff control and not filling over ti�e natural top of tl�e slope. J. KEITH CROSS, P.E. 6358 t21" Avenue SE, Bellevue, Washinglon 98006-4425 Z/�