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Civil Engineering Magazine THE MAGAZINE OF THE AMERICAN SOCIETY OF CIVIL ENGINEERS

Philadelphia Turns Unused Rail Spur into Multifunctional Park

By Laurie A. Shuster

Carried by retaining walls and bridges and more than 100 years old, the spur is finding new life as badly needed green space in an industrial area that is undergoing urban renewal.

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The new, ¼ mi park restores and maintains much of the existing steel and introduces materials of a similar industrial scale and character for the platforms, benches, and guardrails. STUDIO|BRYAN HANES

December 6, 2016—Philadelphia is understood to be a city of collegial but distinct neighborhoods. And as has occurred in many cities, sometimes those neighborhoods have been cut off from one another over the years by large infrastructure projects that served useful purposes but had unintended consequences. So it was with the Reading Viaduct, an elevated railroad line constructed in the 1890s to carry first coal and then passengers through the heart of downtown, known as Center City. With the rise of interstate highways—in particular, the construction in the 1980s of the elevated Vine Street Expressway, which carries Interstate 676 through the heart of the city perpendicular to the rail line—the viaduct became truncated and fell into disuse, now serving only as a divisive eyesore.

But a project begun on Halloween this year is rejuvenating the structure and giving local residents badly needed outdoor gathering space. In the first phase of what the community hopes will one day be a much larger project, a ¼ mi spur of the former rail line is being preserved and redeveloped into an elevated park complete with seating that resembles front porch stoops and swings reminiscent of neighborhood backyards. The section arcs counterclockwise from Callowhill Street, which runs roughly in an east-west direction, and crosses 12 th and 13 th streets, which run roughly north-south.

In 2010 a nonprofit group called Friends of the Rail Park, which is committed to the beneficial reuse not only of this spur but also of the entire 1 mi main line of the Reading Viaduct, partnered with the Center City District, a private-sector organization founded in 1990 to enhance downtown Philadelphia and that recently redeveloped a drab concrete plaza into lively Dilworth Park. Together they obtained funding and engaged Studio Bryan Hanes, a landscape architecture firm, and Urban Engineers, Inc., a planning, design, and construction services firm, both of Philadelphia, to transform the spur a park similar to New York City's High Line but with a distinctly Philadelphian, industrial flair. "Our office is in the neighborhood, overlooking the viaduct, actually, and we have a reputation for working closely with communities," said Bryan Hanes, LEED AP, the founding principal of the landscape architecture firm, who responded in writing to questions posed by Civil Engineering online. "The elevated portion of the rail park connects—or really, divides—three neighborhoods: Callowhill, Chinatown North, and West Poplar. The demographics for each are very different, and there are very different needs and desires from each of the communities. We were tasked with understanding and responding with a design that addressed, to the best of its ability, those needs and desires."

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The spur begins at Callowhill Street and turns counterclockwise to cross above 12th and 13th streets on viaducts. The retaining walls between 12th and 13th streets hold enough soil for trees. STUDIO|BRYAN HANES

Since the area features old industrial structures that are being redeveloped as residential and retail space, many residents wanted essentially a yard. "In the case of [this phase] of the rail park, we knew early on that there was no communal green space in the neighborhood," Hanes explained. "What we hadn't really considered, however, was that most people living here are doing so in these really great old factories and warehouses that have been converted to residential uses. They are solid buildings with great, high ceilings and generous windows, but what they don't have is a backyard, a front stoop, a patio, or a garden.

"Not only is there no communal space in the neighborhood, but few residents have access even to private outdoor space," Hanes said. "As they described their wishes, we realized that what they were really describing was an idealized vision of a residential landscape. That became the inspiration for many of the design elements throughout the project."

What Studio Bryan Hanes and Urban Engineers devised is an elevated park that features trees, shrubbery, walkways, wooden steps to serve as seating platforms, and even a set of unusually large swings, all designed with a character in keeping with the city's history. "Most of this is being fabricated from big, chunky pieces of steel and wood timbers to reflect the industrial heritage of the neighborhood," Hanes said.

Urban Engineers had conducted preliminary studies early in the last decade when the city briefly considered demolishing the spur to make way for structures related to a new baseball stadium for the Philadelphia Phillies. The stadium went elsewhere, but when the rail park idea moved forward, Urban was engaged to determine the structural capacity of the infrastructure and to design any necessary repairs or structural additions to accommodate Studio Bryan Hanes's plan. Andrew Van Schooneveld, a bridge engineer with Urban, says the retaining walls and viaducts that supported the rail line are in remarkably good condition for their age. "There are actually different structures that we looked at," he says. "There are two bridges over 13 th Street and 12 th Street, which are through girders with a floor beam trough system, and then there are piers between 12th and Callowhill. There, it's a four-girder system topped with floor beam troughs. It's sort of a typical construction of the old days—built-up plate girders that are riveted together," he says. Between 12 th and 13 th streets, the structure is supported by a pair of retaining walls rising from grade level that contain fill and soil, he explains.

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The park offers such residential elements as stoops, porches, and swings because features of this type are largely missing from many of the living spaces in the nearby neighborhoods. STUDIO|BRYAN HANES

The engineers found that the infrastructure as a whole is quite robust. "It was designed for the old railroad loading, so the main part of the viaduct is well overdesigned for what we're using it for today," Van Schooneveld explains. The floor beams on the bridges did exhibit some rusting and delamination, however. "We're going to cap that whole system," Van Schooneveld says. "We're going to pour a concrete slab over the entire aboveground structure." A waterproofing membrane will be added to prevent any additional damage from moisture.

Ironically, some of the worst damage sustained by the structure is of recent vintage; a truck hit the overpass above Callowhill Street, damaging the exterior girder. That girder will be replaced as part of the project.

Urban will also make additions to the structure between Callowhill and 12 th , where it will add 5 ft cantilevers to accommodate overlook points and plantings, features that Hanes likens to residential window boxes. "We're putting in an overhead catwalk area, and we're connecting it to the existing girders," Van Schooneveld says. Construction activities there might add more weight than the residents who will eventually use the park, he points out. "We're not too concerned about the strength of the girders, but obviously we had to design the overhang area to handle a small Bobcat loading."

The most unusual load that the engineers had to accommodate was the dynamic one imposed by the 8 ft wide swings on the Callowhill section, which can seat 8 to 10 people at a time. But even those loads were limited because the movement of the swings themselves is limited for safety. "It's not a massive loading compared to a railroad, but it does add a dynamic load," Van Schooneveld says. The swings hang from a steel structure one vertical member and one horizontal member, both tilted back slightly. The structure is bolted into the exterior and first interior girders of the bridge superstructure. "That resists the moment forces," Van Schooneveld says. A frictionless copper pin at the top of the supporting structure connects to a rod that holds the swing. "Welding on the tabs limits the range of motion," he says.

Other areas of the structure were analyzed to determine their ability to hold the plantings. Angelo Waters, P.E., M.ASCE, the vice president and manager of environmental services for Urban Engineers, says, "There will be improvements at street grade as you walk to the park [on the west end]. And then as you enter the park at 13 th Street, you go over a bridge, and there're six through girders there. The middle four will support walking paths, and the outer two girders will be converted into planter boxes." Beyond that point, the rail structure is supported on fill between the retaining walls. "There is a lot of soil to work with there, so there will be larger trees from 12 th to Callowhill," Waters says. "Then as you cross 12 th Street to the viaduct structure, the soil there is a lot shallower, so the plantings will be smaller but maybe more dense, such as shrubs."

The walking paths throughout will be made of chip seal, a low-maintenance pavement surface that combines asphalt with aggregate. The platforms and benches will be made of Ipe, an extremely durable hardwood. "Ipe is hard to scratch, and you can't burn it," Waters explains. Ultimately the maintenance of the park will fall to the Philadelphia Department of Parks and Recreation, so every material had to be approved by it. "This isn't a typical park for a city," Waters says.

The project requires close coordination on the part of the Center City District, Studio Bryan Hanes, Urban Engineers, and the construction company, the local office of AP Construction. "There are no existing or as-built plans, so there will be a lot of verification of dimensions in the field," Van Schooneveld explains. And Noble Street is home to two significant Internet infrastructure companies. "It's a major data center. They tell us that a large portion of the Northeast's Internet traffic goes into those buildings, and there are utilities galore," says Waters. "When you're dealing with landscaping and tree plantings, working around those utilities is no small challenge. And we're still dealing with it. We have good information, but one wrong cut . . . "

The companies also require constant access to their facilities during construction. "So coordination with them is imperative," Van Schooneveld says.

But those companies are just as excited about the prospect of the park as are the residents, and when construction concludes in 2018, the designers hope their efforts will help employees, visitors, and residents of many neighborhoods connect with one another and with the city's industrial heritage. 


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