Squirrel Hill Tunnel
East Portal of Squirrel Hill Tunnel in the snow
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| Overview | |
|---|---|
| Location | Pittsburgh, Pennsylvania |
| Coordinates |
763-4-1, 870+00 west portal 763-4-1, 912+25 east portal |
| Route |
   I-376 / US 22 / US 30 (Parkway East) |
| Start | I-376 Squirrel Hill interchange |
| End | Nine Mile Run valley and Commercial St. Bridge |
| Operation | |
| Work begun | 1945 |
| Constructed | twin bore, concrete with ceramic tile lining |
| Opened | June 5, 1953 |
| Owner | PennDOT |
| Operator | PennDOT |
| Traffic | automobile |
| Toll | none |
| Vehicles per day | 106,000 |
| Technical | |
| Length | 4,225 feet (1,288 m) |
| No. of lanes | 4 |
| Operating speed | 55 mph |
| Tunnel clearance | 13.5 feet (4.1 m) |
| Width | 28 feet (8.5 m) |
| Grade | 2.5% (east to west) |
763-4-1, 870+00 west portal
The Squirrel Hill Tunnel is a tunnel in Pittsburgh, Pennsylvania, United States. It serves as an eastern gateway to the city for I-376 and was completed in 1953 after 8 years of construction and at a cost of US$18 million. At the time of opening it was the single largest investment by the State of Pennsylvania Transportation Department (PennDOT). It is 4,225 feet (1,288 m) long and is a twin-bore tunnel with 8 cross passages.
Squirrel Hill Tunnel construction began in 1946 and opened to traffic on June 5, 1953. The tunnel consist of two bores that pass through Squirrel Hill in Pittsburgh, PA, carrying two lanes of one-way traffic in each direction for S.R. 0376 (Parkway East). At a cost of $18 million, it was the most costly single project built by the State Highways Department and completed the last link in the first 8-mile section of the Parkway.
The tunnel consists of twin arch-shaped reinforced concrete bores that are 4,225 feet long and approximately 29'-4” wide. The tunnel is segmented longitudinally by expansion joints which occur approximately every 50’-4” with some variation at the entrance and exit. The walls are approximately 1’-9” thick and extend 12 feet above the top of barrier to the intersection with the roof arch. The roof arch is 3 feet thick with an inside radius of 19’-3”.
Since August 1987, the tunnels have provided cellular phone reception. The tunnel provided AM reception in 1958; however, due to design repairs, the reception was discontinued by the early 1960s until being reinstalled in 1986. Radio reception was improved to cover the entire tunnel in March, 1997. With the help of Carnegie Mellon University graduate students, the tunnel has provided FM reception since May, 2005; moreover, AM signals were upgraded at that time.
Before 2013, a 6” thick, cast-in-place concrete ceiling separated the arch from the traveled lanes of the tunnel bores to form a plenum, which provided ventilation for the tunnel. This ceiling was constructed 14’-2” above the roadway at its centerline. The ceiling was supported by steel hangers at the tunnel centerline. The plenum contained rectangular openings of varying dimensions that allowed circulation of exhaust and fresh air in the tunnels. In addition to providing ventilation, the plenum carried conduits to power the cellular phone equipment. Both roadway barriers in each bore were retrofitted in 1980 with 2’-0” concrete barriers and walkways for the entire length of the tunnel. The original roadway was also replaced with cement concrete pavement at the entrances and bituminous overlays through the remaining portion during the 1980 rehabilitation.
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