1815 13TH ST SEATTLE CHILDRENS NORTH CLINIC Geotech Report 2022-10-25

Other Seismic Hazards Due to the location of the site and the site's topography, the risk of adverse impacts resulting from seismically induced slope instability, differential settlement, or surface displacement due to faulting is considered to be low. 2012 IBC Seismic Design Information We recommend the use of the following 2012 IBC parameters for soil profile type, short period spectral response acceleration (Ss), 1-second period spectral response acceleration (Si) and seismic coefficients (FA and Fv)for the project site. 2012 IBC Parameter Recommended Value Soil Profile Type C Short Period Spectral Response Acceleration,Ss(percent g) 127 1-Second Period Spectral Response Acceleration,Si(percent g) 48 Seismic Coefficient, FA 1.00 Seismic Coefficient, Fv 1.32 1 Excavation Support The subsurface conditions support use of temporary cut slopes for temporary excavation support. In areas where adjacent buildings or structures are located near the planned cut slope, a minimum 5-foot offset should be established before transitioning to the temporary cut slope. Depending on the depth of excavation,a larger offset or shoring may be required near adjacent buildings.See"Temporary Cut Slopes" section below for recommendations. We provide geotechnical design and construction recommendations for temporary cut slopes below. GeoEngineers can provide temporary shoring recommendations for conventional soldier pile and soil nail as needed. Excavation Considerations The site soils may be excavated with conventional excavation equipment, such as trackhoes or dozers. It may be necessary to rip the glacially consolidated soils locally to facilitate excavation. The contractor should be prepared for occasional cobbles and boulders in the site soils. Likewise, the surficial fill may contain foundation elements and/or utilities from previous site development,debris, rubble and/or cobbles and boulders.We recommend that procedures be identified in the project specifications for measurement and payment of work associated with obstructions. Temporary Cut Slopes The stability of open-cut slopes is a function of soil type, groundwater seepage, slope inclination, slope height and nearby surface loads. The use of inadequately designed open cuts could impact the stability of adjacent work areas, could affect existing utilities and could endanger personnel. The contractor performing the work has the primary responsibility for protection of workers and adjacent improvements. In our opinion, the contractor will be in the best position to observe subsurface conditions GEOENGINEERS /2 April22,2016 Page4 rile No.10738 010.01