Geotechnical Opportunities on a Fast-Track Bridge Project

The bridge for Nine Mile Road over Interstate 75 in Hazel Park, Michigan was destroyed by a tanker fire. The loss of the bridge was considered an emergency situation. Therefore, the bridge replacement was put on a fast-track schedule. Geotechnical engineering challenges included the design of shallow and deep foundations, design of light-weight backfill behind abutments, design of temporary earth retention systems to minimize traffic disruption during construction, and coordinating design changes during construction based on variable subsurface conditions. The design was based on the Bridge Design Specifications from the American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD). Since the project involved replacement of a former bridge, the LRFD design could be compared with the previous foundations that were designed decades earlier. Thus, a summary was developed that identifies how the foundation types and sizes using LRFD methods changed, or remained unchanged, relative to the former bridge design using the Allowable Stress Design (ASD) method. The Michigan Department of Transportation (MDOT) elected to conduct the bridge replacement using the design-build approach. Total time to complete the design and construction of the new bridge: 65 calendar days