1810 104TH ST SE A T AND T WIRELESS ANTENNA 2022-12-02

Geotechnical Engineering F rt Irerracon SN4924 -Silver Lake North Cell Tower Everett, Washington October 24, 2014 Terracon Project No. 81145043 4.5 Seismic Considerations DESCRIPTION VALUE 2012 International Building Code Site Classification (IBC) ' C2 Site Latitude N 47.90324° Site Longitude W 122.207930 SS Spectral Acceleration for a Short Period 1.416g S,Spectral Acceleration for a 1-Second Period 0.544g Fa 1.000 F„ 1.300 1. In general accordance with the 2012 International Building Code, and Table 20.3-1 of ASCE 7 — Chapter 20. Site Class is based on the average characteristics of the upper 100 feet of the subsurface profile. 2. Note: The 2012 International Building Code (IBC) and ASCE Publication 7 requires a site soil profile determination extending to a depth of 100 feet for seismic site classification. The current scope does not include the required 100-foot soil profile determination. Our single boring extended to a maximum depth of 51.5 feet, and this seismic site class definition assumes that very dense glacially consolidated soils as noted on the published geologic mapping continue below the maximum depth of the boring. 4.5.1 Fault Zones We reviewed the USGS Earthquake Hazards Program Quaternary Faults and Folds Database available online (http://earthquake.usgs.gov/hazards/qfaults/map). The closest fault zone is the Southern Whidbey Island fault zone, approximately 4 miles to the west. According to this source, the fault age is less than 15,000 years, has been mapped with northwest striking features, and is in the slip rate category of between 0.2 and 1.0 mm/year. Based on the information described above, we estimate that the risk associated with surface rupture at the site is low. 4.5.2 Liquefaction Liquefaction is the phenomenon where saturated soils develop high pore-water pressures during seismic shaking and lose their strength characteristics. This phenomenon generally occurs in areas of high seismicity, where groundwater is shallow and loose granular soils or relatively non-plastic fine grained soils are present. Based on the site geology and subsurface conditions, the risk of liquefaction of the site soils is negligible. 4.6 Field Resistivity Testing Field measurements of soil resistivity using the Wenner Four-Electrode Method were performed in general accordance with ASTM G 57-78. A series of soil resistivity tests were performed within the site area along perpendicular lines. The soil resistivity measurements were 10