Three the seven tunnels on the Pennsylvania Turnpike's original 160-mile, 56-
year-old Mainline were "retired" in the 1960s when new bypasses opened that could
better handle traffic volumes that had grown to 24 times what the planners of
America's First Superhighway imagined.
Similar fate may await the Allegheny Tunnel approximately 60 miles east of Pittsburgh in eastern Somerset County. It is the longest of the original seven (6,070 feet or 1.2 miles) and, in terms of annual upkeep, is the costliest of the five twin two- lane tubes that serve the present Turnpike system.
A Traffic Relief Study by the Ebensburg-based engineering firm L. Robert Kimball & Associates will outline existing deficiencies, options for addressing them and environmental constraints associated with each option. Barry L. Troup, the Turnpike Commission's Assistant Chief Engineer, said decisions on what corrective action will be taken should be made by the end of 1998. It could be 2003, however, before work gets underway.
Troup noted the Allegheny tube for westbound vehicles, which handled two- directional traffic for nearly 25 years before a second two-lane tube built at a cost of $8.3 million opened in March 1965, must undergo a major rehabilitation within 10 years if it is to remain viable. The only comprehensive repairs to the original tube, totaling $3 million, were made over an 18-month period ending in August 1966 during which all traffic could be routed through the new second tube.
Construction of a new Allegheny Tunnel bypass is just one of the alternatives that Kimball's study will explore in detail. A 1995 engineering report prepared for Turnpike commissioners estimated the cost of a new six-lane bypass (three lanes each direction) at $97 million. The cost of a new three-lane tube through Allegheny Mountain was estimated at $122 million. The latter alternative, assuming the existing twin tubes remain in operation, would provide for seven lanes under the mountain.
"Like anything, it needs continual maintenance," Troup stated. "Repairs are difficult because replacement parts are hard to find."
Fog and winter clearance could be a problem on a new bypass. Three lanes for westbound traffic approaching the tunnel narrow to two. The roadway's curvature for vehicles approaching or exiting the east portals of the existing tubes is the most severe of any Turnpike tunnel.
Carl Baker is responsible for directing day-to-day operations and scheduling a minimum of three tunnel guards for every eight-hour shift, 24 hours day, 365 days a year. "Most people think it's just a hole in the wall," he observed. "There's a lot more to it than that."
Guards make a visual check of the tubes every 30 minutes and drive through every two hours. Debris (tire rubber, tailpipes, miscellaneous pieces that fall from trucks) is cleaned as soon as it's noticed. Vehicles can break down or run out of fuel at the worst places. The Turnpike has its own tow truck on site. Fire and ambulance service can respond within 10 minutes.
In the event of a problem, Baker said guards have two primary responsibilities - stop traffic and remove what is blocking the tunnel or slowing traffic.
Lighting must be adjusted (brightest when it's brightest outside and vice-versa, so the driver's eyes can more easily adjust). Approach and warning lights must be set. Message boards must be updated. The electric motors on each of 10 exhaust fans are adjusted several times per shift based on the readings from the carbon monoxide sensors. Oil for the bearings in the huge fans is checked every fours hours.
"All of our stuff here is old, but everything works," said Baker. Back-up systems must be maintained. There are two diesel-powered emergency generators at each portal in case of an electrical power outage. Other portable generators are available to provide emergency electricty for the call boxes inside the tunnel.
"It's a lot harder than it looks," said Lewis Dickey, a 28-year Turnpike veteran and an Allegheny Tunnel guard for the past eight. "People don't realize the responsibility with this traffic we have (15,000 to 24,000 vehicles daily). You're on pins and needles all day."
Six of the seven tunnels on the original Turnpike Mainline were built using tunnels that were started in 1884 and 1885 for the proposed, ill-fated South Pennsylvania Railroad but never finished. Allegheny Tunnel was blasted and excavated from scratch 85 feet south of the incomplete railroad tunnel because the railroad tunnel was deemed unstable.
Allegheny Tunnel's elevation is 2,314 feet, 416 feet less than the Allegheny Mountain summit 35 miles to the northeast. The tunnel remains a tourist attraction even though the Turnpike's early "Tunnel Highway" moniker has faded. Baker said motorists stop daily to take pictures and, sometimes, even gather rocks.
"It's still a part of the Turnpike people look forward to."