When all is said and done, the Mulberry Street Bridge will look good as new—at 105 years old.
That’s how long the iconic, 18-span concrete arch structure has served Harrisburg, Pa., as the primary link between the Allison Hill neighborhood, the Harrisburg Transportation Center and downtown. And believe it or not, the structure is itself a replacement—the original iron bridge was constructed in 1891 and only lasted 18 years.
Prior to 2014, the Mulberry Street Bridge had undergone two major rehabilitations. A new bridge deck was placed over top of the original in 1957, and in 1982 PennDOT had to replace the expansion joints at the piers.
Then earlier this year during inspection the Mulberry Street Bridge was found to be structurally deficient; in particular, PennDOT felt that the bridge deck needed to be replaced as soon as possible to continue to accommodate the roughly 10,000 vehicles—not to mention pedestrians and bicyclists—that use the bridge every day.
The fact that PennDOT is rehabilitating the bridge is significant, Greg Penny, community relations coordinator, told Roads & Bridges. “Normally after 100 years, we’d be looking at replacing a bridge, but here we are rehabbing it,” he said, adding that replacement would have been a much more costly option.
“It’s a combination of the service that it’s providing and the type of construction,” explained Geoffrey Elsavage, P.E., PennDOT civil engineer. “And it is historic, so in this case, it was possible to meet the needs by rehabilitation rather than replacement.”
Repairs above and below
PennDOT is conducting the rehabilitation project in two phases. Phase one—which began with the complete shutdown of the bridge in April—will focus entirely on replacing the bridge deck. The first step is removing the 1957-edition deck, including the bituminous wearing surface and the structural deck slab. After that, crews can begin building a new bonded concrete overlay to go directly over-top of the original 1909 bridge deck.
In addition to the wearing surface, Phase 1 will also remove and replace the existing sidewalk and parapet, as well as the drainage system and deck joints. Some substructure repair work will be ongoing as well.
According to the agency’s current timetable, they hope to reopen the bridge to traffic this November.
Phase two work will begin in 2015, focusing on repairs to the underside of the bridge, including the arch ribs, floor beams and substructure.
That second phase will also see the permanent removal of safety netting that has hung under the bridge since 2008, when there were reports of debris falling from the underside of the bridge. “A lot of it was Gunite (shotcrete) that had been applied to the bridge,” said Penny. “Then through the water and ice of the winters we’d have, it’d come loose.”
While it has served a purpose, Penny isn’t exactly sad to see it go. “This is the only bridge in our district that has netting, and it’s a distinction we don’t particularly want or like,” he said. “We want to get this bridge to a point where we don’t need [the netting].”
Philadelphia-based TranSystems acted as design consultant on the Mulberry Street Bridge rehabilitation. Neshaminy Constructors out of Feasterville, Pa., is the prime contractor on the $12.2 million endeavor. Construction is progressing in 12-hour shifts Monday through Saturday, with some additional night work.
Funding for the project is an 80/20 split between federal and state sources, respectively. The target completion date for the entire project is Dec. 31, 2015.
Redirecting the flow
Even though the bridge is a primary connector for the capital city, PennDOT ultimately decided to close it to traffic completely. “Rather than conduct the project under traffic that would then require three to four years to complete the work, the decision was made to completely close [it] for one year in order to replace the deck as quickly as possible,” said Greg Penny, PennDOT community relations coordinator.
Redirecting all of the vehicle, bike and foot traffic that normally traverses the bridge has been the most difficult aspect of the project by far, according to Elsavage, who handled most of the coordination. PennDOT worked with Capital Area Transit to create revised bus routes detouring around the bridge closure. “Coordinating with them early was essential, and then also keeping them involved up until advertisement,” Elsavage said.
Foot traffic from the bridge was diverted directly below the bridge to Cameron Street—a concern for some city officials, as Cameron is a main thoroughfare with relatively high speed limits. PennDOT helped alleviate those concerns by increasing visibility of all pedestrian crossings along that stretch.
In addition to traffic on the bridge itself, the presence of the Harrisburg Transportation Center at the west end—and Amtrak and Norfolk Southern lines running directly beneath a portion of the bridge—meant coordinating schedules with both entities to avoid any entanglements.
A model citizen?
Structurally deficient bridges have been a hot topic in Pennsylvania for the last couple of years as it has the most SD bridges of any state. But both Penny and Elsavage hope that PennDOT and others can take a few lessons from the Mulberry Street Bridge and apply them to future efforts.
“We have 25,000 structurally deficient bridges in the state, and the average age of our bridges is about 52 years old, so we have an old inventory,” admitted Penny. “I think the lesson we’ll carry on from here is the amount of work you have to do locally as far as coordination.
“I think that could be a model for other locations where we’re dealing with it.”
