NW 62nd Avenue Pedestrian Bridge and Sidewalk, City of Johnston, Iowa

The project involved the design and construction of a three span 214'x16' pretensioned prestressed concrete beam bridge over Beaver Creek. The structure is comprised of C-beam girders, concrete deck, diaphragm piers on pile foundations, integral abutments and ornamental metal railing. The original concept for this bridge was a single span prefabricated truss bridge.

The first task was to perform a budget review due to the rising cost of structural steel. Multi-span bridge options were then evaluated for both structure types and the study revealed the cost of a 3-span prefabricated bridge with substructures and that of a 3-span concrete beam bridge were nearly identical. The recommendation for a concrete structure was made due to the increased service life of the concrete bridge and the low predictability of cost of the steel bridge. The bidding climate for this project was favorable with a total bridge cost of $365,000 and a total project cost of $715,000.

Project Features:

• Successfully requested out-of-order review from IDNR
• IDNR and USCOE permits obtained in less than 45 days
• Structure designed for no impact to federally regulated floodway
• Design and construction in accordance with Iowa DOT specifications
• Bridge incorporated aesthetic rail and provisions  or future lighting
• Final design completed in 5 weeks
• Wetland mitigation
• Provisions made for future aesthetic enhancement