2320 106TH ST SW Geotech Report 2022-10-25

October 14,2015 Project No.T-6116-2 used on soil conditions observed in the test pits and our knowledge of the area geology, per Chapter 16 of the 2012 International Building Code (IBC), site class "C" should be used in structural design. Based on this site class, in accordance with the 2012 IBC,the following parameters should be used in computing seismic forces: Seismic Design Parameters(IBC 2012) Spectral response acceleration(Short Period), SMS 1.443 Spectral response acceleration (1 — Second Period), SMi 0.732 Five percent damped .2 second period, SDS 0.962 Five percent damped 1.0 second period, SDI 0.488 Values determined using the United States Geological Survey (USGS) Ground Motion Parameter Calculator accessed on October 12,2015 at the web site http://earthquake.usgs.gov/designmaps/us/application.php. 4.2 Erosion Hazard Area Section 37.080.3 of the EMC defines Erosion hazard areas as: "a. Those areas defined as high and very high/severe 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: i. High erosion hazard areas include slopes of 25 to 40 percent in Qva and Qal geologic units; and slopes of greater than 40 percent in other(not Qva or Qal)geologic units. ii. Very high/severe erosion hazard areas include slopes of greater than 40 percent in Qva and Qal geologic units. 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: i. Slopes of 25 to 40 percent in other(not Qva or Qal)geologic units." The soils observed on-site are classified as Alderwood — Urban Land Complex, 2 to 8 percent slopes by the United States Department of Agriculture Natural Resources Conservation Service (NRCS), formerly the Soil Conservation Service. Over most of the site with the existing slope gradients, these soils will have a slight to moderate potential for erosion when exposed. Therefore, the site is not considered an erosion hazard area by the City of Everett. Regardless, erosion protection measures as required by the City of Everett will need to be in place prior to starting grading activities on the site. This would include perimeter silt fencing to contain erosion on-site and cover measures to prevent or reduce soil erosion during and following construction. Page No. 4