A multifaceted approach to material handling helped a Pennsylvania bridge contractor overcome challenges associated with pulling decaying concrete slabs from a weight-restricted structure.
M.A. Beech Corp., based in Carnegie Borough, was tasked with demolishing the now-defunct Donora-Webster Bridge—a 107-year-old, pin-connected highway model with five main spans and total length of 1,547 ft.
In light of a 7,500-lb weight restriction prohibiting the use of traditional excavator equipment, M.A. Beech formulated an alternative solution that included the rental of a heavy-duty vacuum lifting system to remove the largest pieces of well-worn bridge deck.
“The bridge was no longer stable enough for passenger vehicles, much less jack hammers and heavy construction equipment,” said David Hegeman of Anderson Equipment Co. “Our idea was to saw cut it into sections and use a crane to lift it out.”
A solution was found with the Vacuworx Octapad—an eight-pad vacuum lifting system designed to lift deteriorated concrete slabs from roadways and bridge decks. Compatible with Vacuworx RC 10 Series lifters, it features eight 18-in. x 24-in. flat pads with individual vacuum valves that can be shut off when directly over a crack, pothole, or area of slab that is too damaged for lifting.
In addition to pitted or potholed surfaces, the narrow spacing of the truss bridge’s bracing system limited M.A. Beech’s ability to maneuver slabs through the top of the structure. After saw cutting the concrete into 10-ft x 10-ft sections, crews outfitted the Octapad with a lifting eye and lowered it with an American HC 110 Hydraulic Crawler Crane.
Once the vacuum was secured, concrete sections were broken free from the steel frame and then repositioned on the surface of the bridge deck.
“We burnt loose and swung over the slabs to where we could get under them with forks attached to a skid loader,” said Mark Lager, a general superintendent with M.A. Beech. “The deck was by all means irregular. If you had a slab or spot that is rotted or deteriorated, you would just shut off the corresponding valve and pad on the Vacuworx machine. We slid them out of the way with a small Bobcat to the end of the bridge.”
There, a Komatsu 450 loader, tri-axle trucks and the spent materials were hauled away. “By the time he got back, we had one free, and then we’d push it again,” Lager said.
Smaller 5-ft x 5-ft sections of saw cut concrete were pried loose with a Takeuchi TB125 compact excavator.
The Donora-Webster Bridge, which had been rehabilitated in 1986, spanned the Monongahela River near 10th Street. It was closed in 2009 following an inspection that revealed deterioration to the main support beams.
The Pennsylvania Department of Transportation, citing a decrease in traffic and close proximity to alternative spans, announced that the historic bridge—which had been renamed after the late former Lt. Gov. Ernest Kline—would not be replaced.
M.A. Beech was also required to cut away land spans on both sides of the bridge—in Webster and Donora—prior to implosion of the structure on July 1, 2015. The contractor completed its grading and cleanup work in August.
“We were able to get bigger slabs off faster, instead of having to saw everything into little pieces,” Lager said. “In addition to saw costs, it saved us probably a month pulling slabs.”
Roads & Bridges in February reported that 58,500 structurally deficient bridges, including 4,783 in Pennsylvania, were listed on the U.S. DOT’s 2015 “National Bridge Inventory” database.