6307 36TH AVE W Geotech Report 2025-07-29

i I August 13,2008 Project No. T-6241 b. Those areas defined as medium risk of erosion in the Dames and Moore Methodology for the Inventory, Classification and Designation of Geologically Hazardous Areas, City of Everett, Washington: July 1, 1991, when they contain debris and mud flows, gullying or rifling, immature vegetation, or no vegetation: Slopes of 25 to 40 percent in other(not Qva or Qal)geologic units. The City of Everett Erosion Hazard, Critical Areas Map 3, dated March 2006,shows the eastern extreme portion of the site is within or adjacent a medium to high erosion hazard area. No site specific topographic information is available for our review; however, we estimate that the side slopes of the eastern portion of the site generally range from 25 to 40 percent and steeper in places. Based on our geologic data review and test pits excavated near the top of the slope, the slope is expected to be underlain primarily by Qva soils. Therefore, according to the criteria presented in item (a)(i) and (a)(ii) above, the east slope would be considered a high to very high/severe erosion hazards area. iWe did not observe indications of significant erosion at the site; however, the site soils will be susceptible to erosion when exposed during construction. The site plan provided to us indicates that the planned site I development will encroach no closer than 25 feet to the top of the on-site slope and the adjacent off site slope to the east. In our opinion, the potential for erosion at the site can be adequately mitigated with proper implementation and maintenance of Best Management Practices (BMPs) for erosion and sedimentation control. Erosion protection measures as required by the City of Everett will need to be in place prior to and during grading activity at the site. 4.2 Landslide Hazard Section 19.37.080(A)(1)of the EMC defines landslide hazard areas as: a. Those areas defined as high and very high/severe risk of landslide hazard in the Dames and Moore Methodology for the Inventory, Classification and Designation of Geologically Hazardous Areas, City of Everett,Washington: July 1, 1991: Very high/severe: slopes greater than 15 percent in the Qtb,Qw, and Qls geologic units and slopes greater than 15 percent with uncontrolled fill. ii. High: slopes greater than 40 percent in all other geologic units(not Qtb,Qw,and QIs or I uncontrolled fill). b. Those areas defined as medium risk of landslide hazard in the Dames and Moore Methodology for Inventory, Classification and Designation of Geologically Hazardous Areas,City of Everett,Washington: ' July 1, 1991, when combined with springs or seeps, immature vegetation,and/or no vegetation: i. Slopes less than 15 percent for Qtb, Qw, and Qls geologic units and uncontrolled fill. Iii. Slopes of 25 to 40 percent in all other geologic units. Page No.4 I