A precast prestressed concrete arch structure, founded on concrete-filled steel pipe piles replaced a structurally deficient bridge, constructed in 1914. The stone masonry substructure of the aging bridge was severely deteriorated. Concrete form liners, which mimic the stone abutments on the original bridge, are provided on the retaining walls and parapets of the new bridge.
The roadway profile was raised above the 100-year flood event and precast modular retaining walls were installed. In addition, the bridge opening was increased from an 18-foot to a 36-foot clear span and the vertical clearance above Mean High Water elevation was raised. This allows recreational boats along Miry Run, which is classified as a National Wild and Scenic Waterway, to easily pass beneath the new structure.
Urban also completed a hydrologic and hydraulic analysis; developed a scour design for the tidal waterway; managed aerial utility relocations; and led a public involvement program. Rather than over-excavating organic material in the project area, lightweight fill material was used to control the settlement anticipated from raising the roadway profile by five feet. This approach reduced the amount of temporary sheeting and excavation required, which helped reduce construction costs.