Squirrel Hill Tunnel

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Squirrel Hill Tunnel
Squirrel Hill Tunnel IMG 3134.JPG
East Portal of Squirrel Hill Tunnel in the snow
Overview
Location Pittsburgh, Pennsylvania
Coordinates

763-4-1, 870+00 west portal

763-4-1, 912+25 east portal
Route I-376 (Parkway East)
Start I-376 Squirrel Hill interchange
End Nine Mile Run valley and Commercial St. Bridge
Operation
Work begun 1945
Opened June 5, 1953
Owner PennDOT
Operator PennDOT
Traffic automobile
Toll none
Vehicles per day 106,000
Technical
Construction twin bore, circular roof with flat plenum ceiling, concrete with ceramic tile lining
Length 4,225 feet (1,288 m)
Number 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)

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 1953 dollars. 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 eight mile section of the Parkway. The tunnel consists of twin arch-shaped reinforced concrete bores that are 4225 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.[1] The tunnel provided AM reception in 1958 however due to design repairs it was discontinued by the early 1960s until being reinstalled in 1986.[2] It was improved to cover the entire tunnel with strong reception in March, 1997.[3] With the help of Carnegie Mellon University graduate students the tunnel has provided FM reception since May 2005 as well as having its AM signals upgraded at the time.[4]

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 provides ventilation for the tunnel. This ceiling was constructed 14’-2” above the roadway at its centerline. The ceiling is supported by steel hangers at the tunnel centerline. The tunnel ceiling contains rectangular openings of varying dimensions which allow circulation of exhaust and fresh air in the tunnels. In addition to providing ventilation, the plenum carries 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.

As of June, 2013 the ceiling is being raised because trucks were crashing into it.

The tunnel has eight cross-passageways which connect bores and are spaced at approximately 503 foot intervals. These cross-passageways have one fire door near the center, two fire extinguisher niches, and two fire extinguisher cabinets, and emergency indicator lights at each end. Additionally, each cross-passageway contains a hose valve for use by emergency personnel.

The Tunnel Portal Buildings, at each end of the tunnel, house the maintenance garages, office space for Department maintenance personnel, and the exhaust and ventilation fan equipment for the tunnel. These buildings are constructed of cast-in-place concrete. The West Portal Building is constructed on caissons and has a series of chambers which comprise its basement. The rear portion of the building basement has no floor and is, in effect, a set of bridges carrying I-376 East Bound/West Bound above it. The East Portal Building is built on a series of variable-depth spread footings and contains no basement. Otherwise, the Portal Buildings have identical geometry. The facades and exterior surfaces of the Portal Buildings are sandstone and brick veneer with louvered openings and block-glass windows. A variety of cellular phone equipment has been added to the walls and roofs of the Portal Buildings. Additionally, the entrance to each tunnel has traffic signals mounted overhead which are part of the overheight truck detection system.

The Squirrel Hill Tunnel lighting system is composed of fluorescent luminaires for constant lighting throughout the length of the tunnel and low-pressure sodium luminaires for the threshold (day time) lighting at the tunnel entrances. Other tunnel operational systems include Carbon Monoxide (CO) monitoring, fire alarm, emergency communications, and an overheight truck detection system.

In Pittsburgh driving lore, the tunnels are notorious, most notably for several accidents when tractor-trailers that are too tall to safely travel through the tunnel get stuck against the roof of the tunnel. The Pennsylvania Department of Transportation is planning to raise the ceiling of the Squirrel Hill Tunnels in Pittsburgh in hopes of easing the bottlenecks the tunnels create into and out of the city. They are also known for generating traffic jams almost to the preceding exits, due to the highway shrinking from 4 lanes to 2; residents prefer to exit and go through Frick Park and Schenley Park, as it is generally faster.

Due to an engineering project by students at Carnegie Mellon University, it is possible to hear FM broadcasting the entire way through the tunnel.[5]

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