End is near: Southern Beltway near Pittsburgh International Airport set for mid-October opening
April 19, 2021
Steve Hrvoich stood in the year-old valley beneath girders for the new northbound bridge on Interstate 79 on Thursday as gigantic dump trucks known as triple 7s whizzed by, hauling up to 100 tons of dirt each from the east side of the highway to the west.
Crews for Walsh Construction II were a few days away from completing what Mr. Hrvoich, the construction engineering manager for the Pennsylvania Turnpike, called “the big eastern spread.” The crews moved 2 million cubic yards of earth from the eastern side of the valley, clearing space to install thousands of feet of drain pipes before building a ramp to I-79 and finishing the 13.1-mile, $900 million Southern Beltway.
They hauled the dirt to the western side, dumping it in a huge pile called an “optional median embankment” in the center of another looping ramp. A key element of cost control on such a major project is to keep excavated material on site, reusing it in some way rather than paying to haul it off.
After four years, most of the mainline paving and bridge work for the toll road is done. Finishing touches such as road signs, line painting and toll gantries will be come over the summer.
Sprint to the finish
Now, the sprint is on to finish by mid-October the ramps to and from I-79 that will link Washington County communities to the south with the new highway for an easier route to Pittsburgh International Airport.
Ramps to and from the new highway to I-79 for motorists coming from Allegheny County to the north probably won’t be ready until spring 2022.
Mr. Hrvoich said crews for Walsh and its subsidiaries have been pushing to keep the project on schedule, first to catch up after a shutdown of more than three weeks last spring because of the COVID-19 pandemic and then to recover after weather problems over the winter. The goal was to finish moving as much dirt as possible during the cold season, so crews sometimes worked double shifts or weekends.
“Week after week after week, they moved [crews] to stay on schedule,” Mr. Hrvoich said. “We were able to get to the east side on schedule.”
Last year, Walsh started building the interchange under I-79 near Southpointe, at $174.3 million the most complicated and expensive section of the project. That involved digging the valley beneath the interstate and erecting bridges to carry I-79 over it.
All traffic was moved to the northbound side of the interstate to build the southbound bridge. The process was reversed this year, with all traffic on the south side while a bridge was built for the northound lanes.
Cranes used to lift girders into place remained on site Thursday while boatswain chairs — platforms to allow workers to bolt the girders together — dangled from the bridge frame.
Dale Rosinski, construction project manager for consultant CDR Maguire, has nearly 30 years in the construction business. Still, he looked up at the girders and marveled at what crews had accomplished.
“That’s pretty incredible to build that bridge and maintain four lanes of traffic on the other side,” he said.
Soon, the triple 7s and the cranes will be gone and crews can begin what Mr. Hrvoich called the “critical” installation of drainage, which must be completed before paving can begin.
Mr. Hrvoich hopes Mother Nature cooperates this summer so the remaining work can to proceed unimpeded.
“It’s a tight schedule. A lot has to happen,” he said. “It’s very doable, tough.”
Science of asphalt
It looks like one of the more routine jobs, driving a rolling machine back and forth over newly poured asphalt to smooth it out.
Layng asphalt actually is a scientific process that involves monitoring the temperature of the material — precisely 285 degrees — and making sure the pitch of the surface — no more than 0.02% on the road surface and 0.04% on the shoulders — meets safety specifications.
Most of the Southern Beltway will be paved with a new surface called long-life concrete, designed to last 50 years or more. But for a half-mile section between two bridges near the Fort Cherry interchange and the abutments at each end of nine sets of bridge, plans call for asphalt.
That’s because designers are concerned about settlement, Mr. Hrvoich said. Where the bridge abutments meet land, the bridge could settle, causing bumps when the bridge sinks a bit below a stable concrete surface.
If that happens with asphalt, crews can shave off some of the surface to eliminate the bump.
At Fort Cherry, though, the potential problem is the opposite. Because of years of strip mining in the area, designers are concerned about settlement of the subsurface, which would cause concrete to crack or heave, potentially ruining a 50-year surface.
“This was deliberately designed for asphalt,” Mr. Hrvoich said. “It’s probably an engineering decision that wouldn’t be made anywhere else in the world except Western Pennsylvania because of the mining.”
A Lindy Paving Inc. crew used three pieces of equipment Thursday in a mechanical conga line just to get the asphalt on the ground. A covered dump truck brought the heated material to the site from an asphalt plant and poured it into a material transfer vehicle, which jostled it around to make a uniform mixture of the sand, gravel, stone and asphalt adhesive before dumping it into the paving machine.
The paving machine used a device called a screed that slides back and forth to release the material to the surface. A large roller followed the paver, first using its weight to compact the material and then vibrating to smooth out any rough spots. Then a smaller roller made the final passes to eliminate any remaining imperfections.
Along the way, one inspector checked the temperature several times to make sure the material met specifications. If it is too hot, it will ooze out when the roller presses; too cold and it won’t compact.
Another inspector used a digital level to check the pitch every few feet, and a third used a nuclear density gauge to make sure the surface was the proper thickness and compressed the proper amount.
“They have to time it just right and test so they get the proper compaction,” Mr. Rosinski said.
Return to green
Through four years of construction, crews have cleared hundreds of acres of trees and brush to create a path for the highway. They’ve moved millions of cubic yards of dirt to level hills and fill in valleys along the way, mostly a very brown operation.
Now, with the anticipated opening in October, there’s a bigger push to restore some natural beauty to the area. Hillsides are sprouting green with spring vegetation and trees and salt-resistant grasses have been planted in more than 100 storm-retention ponds that will handle runoff along the highway.
Crews beneath the Fort Cherry interchange bridge moved dirt along Robinson Run and the Panhandle Trail on Thursday to plant grass as they restored an area used for service roads during construction. About two-thirds of the site is green now, and crews are working on the remainder.
“It’s nice to see that turning green now instead of being all torn up,” Mr. Rosinski said.
Mr. Hrvoich said there’s an outside chance contractors will finish all the ramps by October, but at least the ramps to serve motorists going to and from the airport from the south should be finished.
“That’s the whole purpose of the beltway,” he said. “If you live south of here, you won’t have to take the Parkway West to get to the airport.”