The Pennsylvania Department of Transportation will begin work this spring on one of the most challenging and innovative projects ever in this region: replacing the Commercial Street Bridge.
The bridge, located just before the Squirrel Hill Tunnel on the inbound Parkway East, has been through three major rehabilitations since it opened in 1951. But concrete spalling, cracks as wide as a quarter inch and the deteriorating condition of the bridge deck convinced officials it should be replaced.
Replacing the bridge will be accomplished by building the new 861-foot span beside it and sliding it into place in summer 2026 once the old bridge is demolished. The contractor will have 25 days to demolish the old bridge and use hydraulic jacks to lift and slide the new one into place.
The other option would have been to build temporary lanes beside the existing bridge to continue traffic flow during replacement work, but PennDOT and consultant HDR decided that would be too disruptive for the 100,0000 motorists who use the bridge every day. They didn’t seriously consider closing the highway for two years to demolish the old bridge and build the new one in the same place.
Preparation work
PennDOT expects to award a contract for the estimated $112 million project in April and the contractor will begin a summer of preparation work a month later, said project manager Mike Szurley. The new bridge will have a steel delta arch design instead of the concrete arch design there now.
That preparation work comes with its own challenges because the bridge passes over Commercial Street, which links between the Squirrel Hill and Swisshelm Park neighborhoods, and part of a trail through Frick Park. The road and trail will have to be temporarily relocated from under the bridge so the contractor has room to build four temporary bridge supports to hold the deck of the new bridge and the permanent supports for the new bridge.
Two sanitary sewer lines, one 24 inches in diameter and the other 48 inches, also will have to be relocated.
Crews also will install a cover over part of the trail so that users can be safe during overhead work. Access to the work site will be provided by upgrading a temporary road on the right side of the inbound tunnel that winds down to the valley about 90 feet below.
Temporary supports for the new bridge will be built on the left side of the inbound tunnel, at least 30 feet away from the existing bridge to allow for safe demolition.
Also in summer 2024, PennDOT will conduct several ancillary projects on the Parkway East. That includes extensive surface improvements between Churchill and Monroeville.
Additionally, the Forest Hills exit ramp will have to be lowered to provide the federally mandated clearance of 16 feet, 6 inches for trucks instead of the 13 feet, 3 inches available now. Inbound trucks will have to exit there when the highway is closed while the bridge is moved into place.
All that prep work will be scheduled for completion by October 2025, when fabricated steel should be ready for delivery. The eastbound, outbound side of the highway will be closed at the tunnel for nine weeknights between October and January 2026 so the steel can be delivered, Szurley said.
On those nights, crews will deliver the steel just outside the far end of the outbound tunnel and use heavy cranes to lower pieces to the valley below because residential access roads are too narrow for delivery trucks. At that point, crews will start assembling the structure of the new bridge.
At the same time, they will begin building two permanent support piers and new abutments at each end of the old bridge.
The contractor has what Szurley called “a very tight time frame” to have the new bridge built and the piers and abutments in place by the scheduled date to close the parkway, July 10, 2026. From there, the contractor will have 25 days to demolish the old bridge and move the new one into place.
The move
That’s when the fun begins for designers and engineers as they watch their plans come together.
Placing the new bridge will involve lifting the structure with hydraulic jacks and moving it about 3 feet at a time until it is above the new abutments and piers. Then it will be lowered into place by matching up predrilled holes on the bridge structure with huge bolts on the abutments.
That work is scheduled to be completed by Aug. 3.
Then, the contractor will have three months to clean up the area under the new bridge and put Commercial Street and the trail back in their original location.
New landscaping that will include trees and other vegetation will be completed in spring 2027.
Szurley said the department is “excited” to see the project move into construction after more than five years of study and design work. This won’t be the first time a new bridge has been built off site and moved into place — the agency used trailers to move the new 140-foot Shaler Street Bridge into place above Route 19/51 in Pittsburgh’s West end in 2019 — but it will be the longest in this region.
Szurley said the construction industry locally and across the country is aware of the project.
“We anticipate there will be a lot of local interest,” he said, as local contractors partner with national experts on off-site construction. National contractors with off-site experience also could submit their own bids and subcontract some work to local contractors.
PennDOT plans to do extensive work to keep residents and motorists informed about the project through its website and newsletters to people in the area. It also will hold public meetings before major work begins next summer and just before the closure and demolition in July 2026.
Ed covers transportation at the Pittsburgh Post-Gazette, but he's currently on strike. Email him at eblazina@unionprogress.com.