3620 BROADWAY VERIZON 2019-01-11

i t Geotechnical Engineering Evaluation NGA File No.983917 Stadium Flowers Addition March 10,2017 Everett,Washington Page 3 At the surface of Hand Augers 2 and 3, we encountered approximately 1.6 and 1.0 feet of loose-medium dense brown and gray sand and gravel with construction debris, which we interpreted as undocumented fill soils. Below the surficial and shallow soils in all hand auger explorations, we encountered medium dense or better, gray and brown sand, with varying amounts of gravel which we interpreted as native glacial outwash soils. All hand auger explorations were terminated within the native glacial outwash soils in the range of 2.5 to 8.5 feet below the existing ground surface, including the present excavation. Hydrogeologic Conditions Groundwater seepage was not encountered in our explorations. If groundwater were to be encountered, we would interpret this water to be perched water. Perched water occurs when surface water infiltrates through less dense, more permeable soils, and accumulates on top of a relatively low permeability material. Perched water does not represent a regional groundwater"table" within the upper soil horizons. Perched water tends to vary spatially and is dependent upon the amount of rainfall. We would expect the amount of perched groundwater to decrease during drier times of the year and increase during wetter periods. SENSITIVE AREA EVALUATION Seismic Hazard We reviewed the 2015 International Building Code (IBC) for seismic site classification for this project. Since competent native glacial soils are inferred to underlie the site at depth, the site conditions best fit the IBC description for Site Class D. Hazards associated with seismic activity include liquefaction potential and amplification of ground motion by soft deposits. Liquefaction is caused by a rise in pore pressures in a loose, fine sand deposit beneath the groundwater table. The competent glacial soils interpreted to underlie the site have a low to very low potential for liquefaction or amplification of ground motion, as mapped on the 2004 Liquefaction Susceptibility Map of Snohomish County, Washington, by Stephen P. Palmer, et al., with which we concur. NELSON GEOTECHNICAL ASSOCIATES,INC.