Philadelphia Street No. 3
The Philadelphia Street No. 3 project was one of a pair of complex urban structure replacements performed by Gibson-Thomas via an open end agreement with PennDOT District 10-0. Both sites were located on Philadelphia Street in Indiana Borough, Indiana County.
The existing single span reinforced concrete slab bridge was constructed in 1911. The structure had been located within an offset intersection of Cherry Alley and thus had a 40 degree bend at the downstream side. The proposed replacement structure was a precast reinforced concrete box culvert with a span of 16’-3” and an effective underclearance of 4’-6”.
The urban site posed many challenges for this project. There were several key issues that the design team successfully addressed through the project’s development:
It was determined that there was no suitable relocation area for the overhead utility lines across the downstream end of the culvert. Gibson-Thomas worked with the District 10-0 Bridge Unit to incorporate a method for placing the downstream end section by which the piece was unloaded within the roadway footprint, placed upon greased timbers, and slid into position under the aerial lines with smaller construction equipment.
Marsh Run has a history of large flooding events due to urbanization of its watershed. The design team changed the skew of the structure to provide a single straight culvert barrel, which eliminated a bend in the existing structure. We maximized the structure opening within the constraints of the site to allow for increased hydraulic capacity and included stream restoration areas at both ends of the structure.
The design team worked closely with adjacent businesses and property owners, including a school for special needs children, to minimize impacts to their operations and incorporate their feedback into the design.
The Philadelphia Street No. 3 structure was completed in the Spring of 2021.