Dawood performed site survey, utility survey, seismic site classification, subsurface investigation and foundation design for improvements to the Southeastern Pennsylvania Transportation Authority (SEPTA) station. The 69th Street Station is a rapid transit and trolley station which connects several city and suburban bus routes. The station improvement project included building a multi-story parking garage, constructing a pedestrian bridge and walking path connecting the train station and bus terminal, and replacing a failing retaining wall.
Dawood Geophysics measured shear velocities of the in-situ soils to a depth of 100-feet (Vs30) to establish a site specific seismic hazard classification consistent with the International Building Code (IBC), 2006. Dawood performed both passive and active surface wave dispersion surveys to assess insitu shear velocities of the site. The survey results indicated soil velocities were high enough to improve the seismic site classification to Class C allowing for reduced structure design and construction costs for the project.
The results of the subsurface exploration indicated the insitu soils at the site were unable to support the large loads developed by the parking garage structure. Therefore drilled shafts into bedrock were designed to bypass the native soils and support the interior and exterior columns of the structure. Spread footings bearing directly on the insitu soil were a viable foundation solution to support the pedestrian bridge foundations and were designed accordingly.