5900 36TH AVE W PRE APP 015 - 032 - SOUNDVIEW BUSINESS CAMPUS - VERITAS Geotech Report 2025-04-22

Veritas Construction Inc ES-4011.03 ' June 17, 2016 Page 12 Revised June 22, 2016 ' Excavations and Slopes I The Federal Occupation Safety and Health Administration (OSHA) and the Washington Industrial Safety and Health Act (WISHA) provide soil classification in terms of temporary slope inclinations. Soils that exhibit higher strength parameters are allowed steeper temporary slope inclinations than are soils that exhibit lower strength parameters. Based on the soil conditions encountered at the test site locations, weathered glacial till, areas of fill, and any area where groundwater seepage are exposed are classified as Type C by OSHA and WISHA. Temporary slopes over four feet in height in Type C soils must be sloped no steeper than one-and-one half horizontal to one vertical (1.5H:1V). Very dense, cemented, 111 undisturbed glacial till encountered without the presence of groundwater may be classified as Type A by OSHA and WISHA. Temporary slopes over four feet in height in Type A soils must be sloped no steeper than 0.75H:1V. Type A soils that are fissured, subjected to vibrations from heavy traffic, or have been otherwise previously disturbed must be classified as Type B by OSHA and WISHA. Temporary slopes over four feet in height in Type B soils must be sloped no steeper than 1 H:1 V. Where encountered, the presence of perched groundwater may cause caving of temporary slopes due to hydrostatic pressure. ESNW should observe site excavations to confirm soil types and allowable slope inclinations. If the recommended temporary slope inclinations cannot be achieved, temporary shoring may be necessary to support excavations. Permanent slopes should be planted with vegetation to enhance stability and to minimize erosion and should maintain a gradient of 2H:1V or flatter. An ESNW representative should observe temporary and permanent slopes to confirm the slope inclinations are suitable for the exposed soil conditions. Supplementary recommendations with respect to excavations and slopes may be provided as conditions warrant. Seismic Considerations The 2012 IBC recognizes ASCE for seismic site class definitions. In accordance with Table 20.3-1 of ASCE, Minimum Design Loads for Buildings and Other Structures, Site Class C, should be used for design. In our opinion, the site has a low susceptibility to liquefaction. The soil composition, relative density and the depth to groundwater table is the primary basis for this opinion. Drainage Based on our field observations, discrete zones of perched groundwater seepage should be anticipated within site excavations, especially within those excavations for utilities. Perched groundwater seepage should also be expected within shallower site excavations depending on the time of year grading operations take place. Temporary measures to control surface water runoff and groundwater seepage during construction would likely involve interceptor trenches and sumps. ESNW should be consulted during preliminary grading to identify areas of seepage and provide recommendations to reduce the potential for instability related to seepage effects. Permanent interceptor drains may be necessary in some areas. Earth Solutions NW, LLC