With a long-range forecast of unacceptable traffic congestion ahead, the Pennsylvania Turnpike Commission again will consider options for improving or eliminating the Allegheny Mountain Tunnels in Somerset County.
One option that was favored by the commission more than a decade ago -- rerouting the turnpike through a notch that would be carved in the mountain about 600 feet north of the existing tunnel -- will be reconsidered.
Other choices are rehabilitating the existing tunnels, replacing them with new, wider tunnels or doing nothing, turnpike spokesman Carl DeFebo said.
Planning is at a preliminary stage. Within coming weeks, the commission expects to issue a request for proposals for a new alternatives analysis, which would take two years, Mr. DeFebo said, followed by four to six years of design work.
Any construction would be at least six years away.
About 11.3 million vehicles passed through the tunnel, about 70 miles east of Pittsburgh, last year -- an increase of nearly 18 percent since 1996.
While traffic volume has leveled off or declined in the past few years, the count is projected to grow to 13.3 million by 2015 and 14.9 million in 2025.
Talk about rerouting the turnpike away from the tunnel goes back to 1996, when the turnpike commission hired a consultant, L. Robert Kimball and Associates, to study its options.
The preferred option that emerged was a 2.8-mile bypass that would have required the commission to cut a 220-foot notch in the mountain. The estimated cost was $90.9 million, far less than the cost of boring a new tunnel.
The plan was dropped in 2000 after objections from a hunting and fishing club that would have lost 144 acres of wildlife habitat.
The group argued that a new tunnel, with an estimated cost of $153.8 million, would be less disruptive to streams, wetlands and animals.
The Allegheny Mountain Tunnels, at 6,070 feet long, are the longest of four twin tunnels on the turnpike's east-west mainline. A single two-lane tunnel opened in 1940, and the second two-lane tunnel was added in 1965.
Although the current tunnel is structurally sound and has had numerous improvements over recent years, there are several drawbacks to keeping it open, Mr. DeFebo said.
As the turnpike gradually widens to three lanes in each direction, and with traffic expected to increase, the two-lane tunnels will become a bottleneck.
The tunnels have lighting, ventilation, drainage and personnel costs that are not associated with open highways. Several times a year, the tunnels must be temporarily closed so that workers can remove giant icicles that form on the walls.
Trucks carrying hazardous materials cannot use the tunnels and must leave the turnpike for 36 miles between Somerset and Bedford, using inferior alternate routes.
"You're going through downtown Somerset. How much sense does that make?" Mr. DeFebo said.
Also, the existing alignment makes it impossible for the turnpike commission to eliminate the remaining sharp S-curves as the highway descends just east of the tunnels. Some curves lower on the mountain were straightened as part of a reconstruction project four years ago.
Jon Schmitz can be reached at email@example.com or 412-263-1868.