Tuscarora Tunnel Rehabilitation

Gannett Fleming’s work on the project included an in-depth inspection of the entire tunnel system, including eastbound and westbound tubes, portal buildings, and air shafts. Specific inspection tasks included:

• Examination of tunnels walls, ceiling slab, tunnel crown, and portals.
• Testing and evaluating the tunnel and support space lighting, computer control system, and normal and emergency power systems, including medium-voltage service equipment, low-voltage switchboards, tunnel ventilation fan motor starters, generators, and uninterruptible power supplies.
• Testing and evaluation of the ventilation system and associated equipment.

Field data was collected on hand-held computers and placed into a computerized structural database, as were condition evaluation ratings for the tunnel elements. An inspection report was prepared, including findings, recommendations for repair, operational testing results, and a code evaluation.

Tight clearances in the eastbound tunnel, and the need to enhance tunnel ventilation, led to PTC’s decision to remove the existing ceiling and widen lanes. Controlling water infiltration through the liner required a waterproofing membrane with lattice girders and a shotcrete liner, directing infiltration to the roadway drainage system.

In winter, cold-water infiltration in the westbound tube requires multiple, short-term closures daily to remove ice from the tunnel ceiling. New waterproofing measures will direct seepage away from walls and ceilings, providing a dry roadway and eliminating the need for lane closures. New roadway drainage inlets in both tubes, with large, cast-iron, clog-resistant grates, will facilitate drainage system maintenance.

Fire and life safety improvements included an upgraded ventilation system to improve smoke removal in the event of a fire. The system also allows fans to be maintained in a separate room off the roadway. Upgrades in power distribution and the replacement of generators support the new ventilation system.

The existing high-pressure sodium lighting system was replaced with a state-of-the-art LED system to improve light quality and provide energy savings by as much as 53%. A dark coating on the exterior portals, in combination with an illuminated tunnel interior, will help counteract motorists’ tendency to slow down when approaching a dark entrance, improving traffic flow through the tunnels.

• Waterproofing and drainage systems prevent water infiltration and structural damage to tunnel walls and ceiling.
• New supervisory control and data acquisition (SCADA) system provides improved control over tunnel systems.
• Automated lane closure systems, dynamic message signs, and lane closure signs direct two-way traffic through a single tube when needed during rehabilitation construction and future maintenance.
• New LED lighting improves energy efficiency and driver safety.
• New ventilation system improves smoke removal in case of a fire.

• Improved traffic flow due to roadway widening, improved clearances, and new lighting.
• Augmented tunnel safety via lighting, ventilation, and fire and life safety systems upgrades.
• Enhanced operational efficiency that reduces future maintenance and energy costs.

• Engineers’ Society of Western Pennsylvania, 2023, Project of the Year – Modernization
• American Shotcrete Association, 2022, Outstanding Shotcrete Project Award