CSX Howard Street Tunnel Clearance Project Progressive Design-Build
Baltimore City, MD
| Location: | Baltimore City, MD |
| Owner: | CSX |
| Construction Company: | Joint venture of Skanska and Fay, S&B USA Construction |
| Project Status: | Under construction since January 2024 with an estimated completion by the end of June 2026 |
Fay, S&B USA Construction (Fay) is in the construction phase of a progressive design-build project to increase the clearance of CSX’s Howard Street Tunnel and the adjacent Mount Royal Avenue Tunnel from approximately 19 ft to 21 ft, and increase the lifespan of a critical piece of infrastructure without building a new tunnel. This work is part of the overall Howard Street Tunnel Project, a key CSX capital improvement initiative to address clearance restrictions for double-stack trains along its vital I-95 rail corridor between Baltimore and Philadelphia, as well as from the Port of Baltimore’s Seagirt Marine Terminal Intermodal Container Transfer Facility (ICTF) to consumer markets in the Midwest.
Adapting a Historic Transportation Landmark to Fit Modern Needs
Project Highlights
- Increase the clearance of the 1.7-mile Howard Street Tunnel and adjacent Mount Royal Avenue Tunnel from approximately 19 ft to 21 ft by lowering the track to allow passage of double-stack trains
- Install 7,138 ft of new precast concrete flooring to replace the aged tunnel invert (floor) and brick beneath the track
- Improve the tunnels’ drainage system and overall resilience to increase the structure’s lifespan to 75 years
- Expedite the construction schedule to return this vital railroad corridor to service
- Relieve the last major bottleneck for double-stack trains in CSX’s Interstate 95 transportation corridor between Florida and New England, and from the expanding Port of Baltimore to Midwest markets
Challenge
The historic Howard Street Tunnel, originally constructed in 1895 and later extended in the 1980s, serves as the main North-South railroad line on CSX’s I-95 rail corridor connecting major population centers on the East Coast. At nearly 130 years old, it is still the original brick-lined tunnel that was not designed for modern, taller trains. The Mount Royal Street Tunnel, several hundred feet north on the same tracks, has the same vertical clearance limit. The goal of the project is to increase both tunnels’ height to allow double-stack intermodal trains to pass through, with a secondary goal to lengthen the structures’ lifespan by improving water drainage inside the tunnels. CSX requires the work to be completed quickly to restore this part of its East Coast corridor to service.This project is part of the final phase of a CSX modernization initiative to allow 100% of their intermodal network to be cleared for double-stack train service, which will also support a planned expansion at the Port of Baltimore. Once completed, this project will help to transform freight rail efficiency and capacity along the Mid-Atlantic corridor and to Midwest destinations, improve supply chain efficiency for shippers, and increase the lifespan of this critical infrastructure without building a new tunnel.
Solutions
To increase the tunnel’s clearance from approximately 19 ft to 21 ft without damaging the tunnel’s original brick archway, engineers proposed to excavate and lower the track, replacing the tunnel’s current invert (floor) and underlying brick with modern precast concrete sections. This solution will enable passage of double-stack trains while preserving the structure of the tunnel’s historic brick archway. The project design also addresses tunnel drainage problems by first using a vacuum wellpoint dewatering system to lower the water table in the tunnels, followed by installing longitudinal drainage along the invert to manage water in the long term.To expedite construction, ensure safety and return the tunnel and tracks to service faster, CSX and the project team determined the construction would be most efficiently completed in a nine-month shutdown of the tunnel from February through November 2025. During this time, crews will have 24/7 access to the tunnel without the interference of live rail traffic. This solution replaced a previous plan to work in two-day cycles then pause for live rail traffic, enabling construction to be completed nearly a year and a half earlier. The change also eliminated the need for CSX railroad worker protection, making the project site safer for construction crews. While the closure is in effect, CSX entered into a joint use agreement with Norfolk Southern to use their nearby track.
Construction
The construction consists of demolition, lowering the water table, structural modifications, underpinning, drainage installation and track work.Preparatory work removed inactive utility lines from inside the tunnel, and workers performed drainage and grading work at the east portal. They also installed engineering instrumentation to monitor the condition of both tunnels’ brick lining throughout construction and dewatering well points to lower the water table and dry out the tunnel.
After CSX closed the rail line in February 2025, crews began working from the east portal of the tunnels. CSX crews began cutting and removing a 20-linear-foot section of rail. Construction crews will then remove the crushed stone ballast, cut the invert (floor level) of the tunnel, demolish the original brick underneath and excavate to the lower depth.
After removing all debris, working in 6-linear-foot segments, workers will set three sections of precast concrete invert on crushed stone using a gantry specially designed for this project. Bolts will anchor each invert to the next. Once a section of inverts is set and anchored, concrete cast in place between the tunnel wall and the sides of the inverts will tie the section to the tunnel foundation. Grout injected into molded holes in each invert will fill the space beneath. The precast invert segments are fabricated offsite and will be delivered periodically to the construction site.
Crews will complete each section by adding longitudinal drainage, placing and compacting new ballast, and reinstalling the original track. CSX then completes the segment by bolting joints to the track, flooding the ballast, and stabilizing and tamping the surface.