The First Street Bridge over the North River is a 300’ x 20’ continuous steel I-beam bridge constructed in 1955. The deck was in serious condition with significant delamination, exposed reinforcing, cracking, and leaching. The superstructure was showing its age as well with corrosion of the drains, beams, and bearing devices. The City desired a wider deck meeting current standards as well as a pedestrian/bicycle crossing that will eventually link Carlisle with the Des Moines area trails.
We initiated the project in 2001 with a feasibility study to evaluate two rehabilitation alternatives along with complete replacement of the bridge. After reviewing the study, the City decided to initiate a major rehabilitation project and requested our assistance in pursuing additional project funding.
The design included a new deck consisting of a 32’ roadway and 10’ pedestrian sidewalk/bikeway. To accommodate the wider deck width, the existing abutments and piers were widened, and five new beam lines were added to the existing three beam lines. The design also includes aesthetically pleasing, crash approved barrier rails, ornamental hand rails, and ornamental lighting. Relocation coordination of a city power line, private gas line, and private fiber optic cable and telephone lines were also part of our services. In addition to the feasibility study, funding assistance, and design the City also retained CB&A to provide resident inspection and construction engineering services. This project was awarded the Quality Initiative Structures Award for a Steel Beam Bridge on a Local Road.