Article by ASCE-PGH Awards Committee

The 4225’ rock-bored Squirrel Hill Tunnel in the east end of Pittsburgh, PA is key element of I-376, the primary travel corridor from the East to and from the city. Although the tunnel has held up well over time, the Pennsylvania Department of Transportation (PennDOT) determined that many of the structural, electrical, ventilation, control, and fire life safety systems were in need of repair or replacement.

In 2010, PennDOT hired Gannett Fleming, Inc. to prepare rehabilitation contract documents for the 60+ year old tunnel. The resulting design modernized most of the existing tunnel systems to current AASHTO and National Fire Protection Association 502 “Standards for Road Tunnels, Bridges, and Other Limited Access Highways”. This construction involved full retrofit of multiple tunnel structural systems, upgrade of the fire life safety system, rehabilitation of the ventilation system (including removal of the tunnel slab ceiling), full replacement of the electrical and lighting systems, and other specialized upgrades.

This project had many challenges, specifically addressing aging structural systems, fire/life safety systems, the removal of the tunnel ceiling throughout the tunnel’s entire length, slab replacement retrofit of the “hidden bridge” at the West Portal of the tunnel, upgrade of the tunnel electrical systems, and other structural/architectural repairs required to extend the service of the tunnel. Much of the construction was performed during night-time, single lane closures and limited weekend shut-downs, adding more complexity to an already challenging project.

Gannett Fleming, Inc., operating out of its Pittsburgh, PA, office, was the prime consulting engineer on a team with URS Corp. and Tri State Design and Development. The project contractors were Wash Construction Corp., Sargent Electric, Independence Excavation, and W.G. Tomko.