Iron CTH A over Oronto Creek Bridge Replacement

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The Iron County Highway Department retained Ayres to quickly design the replacement of the CTH A bridge over Oronto Creek amid a complex flood recovery effort.

The existing bridge approaches washed out when nearly 10 inches of rainfall caused a flood in July 2016 that severely damaged Saxon Harbor and the surrounding area. Ayres had designed the original bridge in 1995. When the approaches washed out, including a 280-foot-long washout of the north approach, Oronto Creek was significantly realigned. Because of this, it was decided to replace the bridge on a new alignment so the harbor could be reconstructed with new flood protection measures to help prevent future flooding. The project was fast-tracked for 2018 completion. Construction began about nine months after Ayres was under contract to start the design, making for an extremely aggressive schedule.

The new bridge is a 104-foot-long, three-span concrete haunched slab bridge. It replaced a 40-foot-long single-span concrete flat slab bridge. The new bridge is on a new alignment and includes a 6-foot-wide pedestrian path on its east side. To prevent scour at the bridge, heavy riprap was used at the abutments and at all four wing locations. The new bridge was hydraulically sized so that it matches the new flood protection devices that are part of the Saxon Harbor reconstruction immediately downstream of the bridge

Federal Emergency Management Agency (FEMA) and Federal Highway Administration (FHWA) funding paid for parts of the harbor’s reconstruction. This added another layer of coordination to the bridge replacement project, as designs had to comply with FEMA and FHWA rules to qualify for funding

Coordination was a large task in this project, which was integrally tied to the overall Saxon Harbor flood recovery process, including marina dredging and repair, channel dredging and restoration, floodplain improvements, and relocation of a County campground. The original bridge was used as part of a temporary roadway so that recovery efforts could continue during construction of the new bridge and CTH A on their new alignment.

Services included preparation of a design study; preparation of an environmental report; design of the structure; development of structure plans; and plans, specifications, and estimate.

Project Information

Client's Name

Iron County Highway Department


Saxon, WI

Primary Service

Structural Design & Analysis


Local Government