Replacing an Old Bridge with a New Tunnel Using Corrugated Structural Metal Plate

The current economy, characterized by high inflation and a degree of uncertainty, has brought on a reality for public agencies and other infrastructure owners that there is a need to do more with less. This extends to areas of maintaining, rehabilitating, replacing, or expanding their assets. Savvy infrastructure managers are always looking for ways to salvage existing facilities while making upgrades.

This article examines how CSX Corporation (CSX) salvaged its existing bridge under circumstances that needed creative solutions.

The bridge project had non-negotiables, including site access constraints and the inability to shut down rail service, except for one 24-hour period. CSX chose corrugated structural metal plate (CSMP) because of its adaptability to overcome these difficulties.

CSX owns and operates parallel railroad tracks that run east to west through Newton Falls, Ohio. They are part of a critical freight route between the East Coast and the Midwest. The Newton Falls portion includes structure BG95.6 over the city’s pedestrian and fitness trail connecting the north and south sides of the community. The original structure over this trail was a steel girder bridge on sandstone abutments, originally constructed in 1904. The steel girders from the original installation were well beyond their prescribed service life and needed to be replaced to protect the sensitive nature of this critical freight route.

The construction of the new tunnel by CSX crews was completed in four phases.

Long-duration shutdowns were not an option on this segment of the parallel east-west track because of CSX’s commitments to its freight customers. Also, an important constraint associated with replacement-in-kind of the girders is the residential neighborhood immediately next to the bridge, which limited the ability to mobilize large equipment such as cranes onto the bridge site. Another important consideration was CSX’s desire to implement a solution that would allow its own maintenance crews to build the replacement structure. Finally, CSX was seeking a solution that reduces maintenance costs over the service life of the new structure.

All these factors led CSX to determine that building a 140-foot-long tunnel using CSMP was the best option to accomplish the replacement of the bridge. The specific material chosen by CSX consisted of galvanized steel corrugated structural steel plate due to its ability to provide a minimum service life of 50 years and a manufacturing lead time of only 2 weeks.

By replacing a bridge with a soil-structure interaction system with CSMP to create a tunnel, CSX was able to implement a cost-effective solution that addressed the constraints associated with both its rail operations and the site location. The tunnel will also be less expensive to maintain over the 50-year minimum service life compared to a bridge. Furthermore, the railroad operator will have little concern about track settlement over the tunnel. The existing sandstone abutments and concrete collars at the tunnel portals will confine the compacted, well-graded stone backfill around the CSMP tunnel shell to prevent ground loss. Most importantly, CSX was able to accomplish this infrastructure upgrade using its own crews while limiting the track shutdown to 24 hours.

This example of CSX’s creativity provides inspiration to other infrastructure managers to consider replacing their aging bridges with a tunnel!

(Note from the Author: The tunnel described in this article was constructed by CSX in 2012. The designer and engineer of record is CONTECH Engineered Solutions. CONTECH also manufactured and supplied the galvanized steel structural plate for the project.)