Armstrong Tunnel Rehabilitation

For nearly a century, the Armstrong Tunnel has served as a critical gateway between downtown Pittsburgh and the city’s South Side via the South Tenth Street Bridge. Opened in 1927, the tunnel is a vital transportation link, carrying more than 11,000 vehicles per day beneath the Duquesne University campus while also serving as a historical landmark for the City of Pittsburgh.

Last rehabilitated in 1990, the nearly 1,300-foot-long twin-bore tunnel faced growing structural issues, outdated life-safety systems, and accessibility limitations that no longer met modern standards. At the same time, its role as a heavily traveled urban corridor meant that any work would need to be completed while maintaining continuous vehicle and pedestrian access through one of the city’s most constrained locations.

As part of the Armstrong Tunnel rehabilitation project, GFT was tasked to modernize the structure without losing its historical character. GFT’s design preserved and upgraded both tunnel bores through an integrated program of structural repairs, mobility improvements, and life-safety enhancements, all while keeping the tunnel open and minimizing disruption to daily travel.

Structural work addressed long-term deterioration through arch concrete repairs, joint repairs, and drainage improvements, and replaced the aging interior liner with calcium silicate fire-resistant panels coated in Ceramicoat, the first use of that protective coating in the region. Ceramicoat improves fire protection while offering greater durability and easier long-term maintenance.

Safety and accessibility improvements were needed to bring the tunnels up to standard. Multimodal improvements for roadway and sidewalk reconstruction enhanced the interior surfaces, including adding American with Disabilities Act (ADA)-compliant curb ramps and a widened sidewalk in the southbound bore to improve accessibility along a critical route between downtown Pittsburgh and Duquesne University.

The rehabilitation also upgraded interior systems, including replacing the outdated high-pressure sodium lighting system with an adaptive LED network that automatically adjusts to exterior lighting conditions, improving visibility and driver awareness. Additional life-safety system upgrades included:

• Closed-circuit television (CCTV) coverage.
• Fiber optic linear heat detection.
• Photoluminescent egress markings.
• Fire alarm pull stations.

Throughout construction, preserving the tunnel’s historic identity remained a priority. The exterior sandstone and granite portals were carefully cleaned using a wet abrasive method that revealed the original architectural detail while avoiding chemical damage. The result is a tunnel that looks brighter, feels safer, and performs to contemporary standards.