We're pleased to announce that the Inwood Iron Bridge Truss Rehabilitation and Replacement Project received ASHE Harrisburg's 2021 Project of the Year Award in the Under $20 Million category. The project and team were recognized at the ASHE Harrisburg Section Meeting on June 14, 2021.
The 160-foot Inwood Iron Bridge carried T-575 (Iron Bridge Road) over Swatara Creek in Union and Swatara Townships, Lebanon County, PA. This historic county-owned bridge was closed to traffic in 2005 due to significant damage and deterioration. The closure created a safety issue for the flood-prone Monroe Valley community along T-473 (Old State Road). With the bridge closed, there was only one remaining route for the community downstream, which itself often flooded. The purpose of this project was to reestablish and maintain the T-575 crossing of Swatara Creek.
The single-span, pin-connected Pennsylvania steel thru truss Inwood Iron Bridge (c. 1899), fabricated by the Pittsburgh Bridge Company and erected by Nelson and Buchanan, is historically significant as one of the oldest surviving Pennsylvania thru truss highway bridges in the state and is eligible for the National Register of Historic Places (NRHP). Pre-1900 examples of Pennsylvania thru truss highway bridges are not common since the design was more often used for railroad applications. Fewer than six such roadway bridges have been identified in the state. Preservation of this important historic resource became a major focus of this project.
To meet the purpose and needs of the project while not adversely affecting the historically significant bridge, the truss was relocated, and a new modern bridge was constructed at the Swatara Creek crossing. Relocating Inwood Iron Bridge allowed it to be restored and opened for public use in a new park just downstream. Through effective partnering between federal, state, county, and local agencies, this project provided a long-term solution for preserving the historic resource while reestablishing a safe and reliable crossing.
Aesthetic considerations associated with the relocated truss included a two-tone paint scheme, a reused stone masonry façade, and hot-driven rivets. The replacement structure aesthetics included stone form liners applied to the new abutment and wing wall faces and form liners on the outside barrier faces emulating the truss low chord connections. Because the project is within Swatara State Park and adjacent to the rail trail, these aesthetic enhancements also benefited the unique setting.
Sustainability goes hand in hand with historic preservation. The rehabilitation and reuse of historic resources preserve the history of the existing structure. Most of the existing structural steel and stone masonry abutments were retained and reused in the rehabilitated bridge. Repurposing the truss for non-vehicular use also helps sustain the historic bridge’s life expectancy. The informational kiosks constructed at both bridge locations record and share the bridge’s history and significance in engineering as well as local transportation history.
The project team met the goals of the project by reestablishing and improving the safety of the previously closed T-575 crossing of Swatara Creek while preserving the NRHP eligible truss. All 17 project commitments were satisfied in full, and the project remained largely within budget and schedule expectations (outside of delays incurred due to COVID-19). The safety of the surrounding area was greatly improved, providing increased emergency services access and improved sight distance. The aesthetics of both sites were ensured through the reuse of the original stonework, appropriate application of form liners, and the use of hot-driven rivets. The overall resulting project will serve the local community and general public well into the future and far exceeded both PennDOT and the County’s needs and vision of this project.