3214 BROADWAY BROADWAY KINECT APARTMENTS 2021-08-11

SD • American Property Development ES-0599.06 January 22, 2015 Page 13 • Updated June 9, 2016 • • Excavations and Slopes • • The Federal and state Occupation Safety and Health Administration (OSHANVISHA) classifies • soils in terms of minimum safe slope inclinations. In our opinion, based on the soil conditions • encountered during fieldwork for this site, the weathered native soils and existing fill encountered to depths of up to four feet to seven feet would be classified by OSHANVISHA as • Type B. Temporary slopes in Type B soils should be sloped at an inclination of at least 1H:1V, • or flatter. In our opinion, the dense to very dense native soils below the weathered native soil • and fill would be classified by OSHA/WISHA as Type A and B. Temporary slopes over four feet in height in Type A and Type B soils should be sloped at an inclination no greater than • 0.75H:1V or 1H:1V, respectively. With respect to the proposed building excavations, temporary • slopes inclined at 0.5H:1V are feasible within the very dense silty sand with gravel glacial till deposits. The geotechnical engineer should observe the excavations to verify the appropriate • allowable temporary slope inclination. • If the above slope gradients cannot be achieved, temporary shoring may be required. • Permanent slopes should maintain a gradient of 2H:1V, or flatter, and should be planted with an • appropriate species of vegetation to enhance stability and to minimize erosion. • Seismic Considerations • The 2012 International Building Code specifies several soil profiles that are used as a basis for • seismic design of structures. The 2012 IBC recognizes ASCE for seismic site class definitions. • If the project will be permitted under the 2012 IBC, 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 absence of a • shallow groundwater table observed at the test sites, and the soil relative density observed throughout the test sites is the primary basis for this conclusion. • • Drainage • The presence of excessive groundwater seepage is not expected in the general site and utility • excavations. However, zones of perched seepage are possible and may produce moderate • flow rates within the site excavations. Temporary measures to control groundwater seepage • and surface water runoff during construction would likely involve interceptor trenches and • sumps, as necessary. Based on groundwater seepage conditions observed at the test sites, • we do not anticipate extensive dewatering of excavations will be necessary. • At this time we do not anticipate a permanent sub-slab drainage system will be necessary for • this project. However, the location and depth of groundwater seepage and zones of chronic • groundwater are difficult to predict. Therefore, if unanticipated groundwater conditions are encountered, the geotechnical engineer should reassess the need for additional drainage below • the slab during construction. • • • Earth Solutions NW,LLC • •