Last year, the MTA kicked off an extensive renovation of the Culver Viaduct which carries the F and G trains over the Gowanus Canal. The overhaul includes structural work, a renovation of the Smith/9th Street station, and an upgraded signaling system. The estimated four-year, $300 million project has received a lot of attention, but many see this site — the structure, the transit gateway, and the neighborhood itself — as an area ripe for broader intervention. John McGill, an architect and lecturer currently residing in San Francisco, was struck by the opportunity that the Culver Viaduct presents while a masters student at UC Berkeley. Fascinated by both the idiosyncratic viaduct structure, a fixture of his childhood spent in Carroll Gardens, and the concept of infrastructural re-occupation and “leftover” urban sites, McGill chose to address the site in his masters thesis. At Urban Omnibus, we love to encourage and surface student work that explores alternatives to traditional approaches to, for example, a subway station renovation. Below, McGill expands on his thesis work to explore the idea of infrastructure as opportunity, the need to activate urban void spaces, and, through his design proposal, the ways that adaptive re-use, unconventional development strategies and a flexible approach to program can help activate infrastructure for public use and local benefit. –V.S.
Culver Viaduct | Photo by John McGill
Infrastructure as Urban Opportunity
As infrastructure in our cities reaches and exceeds the end of designed life spans, the necessary upgrades, repair, and replacements to these aging systems require significant public investment. According to the American Society of Civil Engineers, some $2.2 trillion of investment will be needed to address US infrastructure needs in the next five years alone. At the same time, urban park development increasingly involves cooperation with, and concessions to, the private sector to offset the need for public investment. Vacant land suitable and available for new public space and other essential local amenities is, for obvious reasons, hard to come by. It is therefore no surprise that last summer’s opening of the High Line’s first segment was so highly anticipated and widely discussed: infrastructure is increasingly seen as a locus of opportunity.
The seemingly inaccessible and useless spaces of urban infrastructure have a value beyond their (often awkward) adjacency to newly viable real estate: they are already inscribed with highly specific relationships to surrounding urban fabric, and as intervention sites can therefore mediate between radically different scales, speeds, and programs.
Underneath the Culver Viaduct | Photo by John McGill
Activating Urban Void Spaces
Large pieces of transportation infrastructure have traditionally been built to address a singular, performance-driven use, and those conceived and built at a particular moment in history were often over-engineered to accommodate (or privilege) other layers above, below and adjacent. Precisely because of these attributes, they serve as translators between adjacent systems, producing as byproduct large volumes of space with odd relationships to surrounding buildings, streets, and their respective orientations. These transportation systems offer a scaffold that is scaled to the city, relevant to its history, and generally oversized but underused – structures that have the latent potential to organize public space more actively and to support a vibrant mixture of urban programs based on immediate local needs and conditions.
As these systems age and must be upgraded or replaced they provide a unique opportunity for us to expand the meaning and scope of “adaptive reuse” in the urban context. The ubiquity of such decaying structures in our cities, and their resulting firm – but conceptually uncertain – presence in the public conscience, suggests an inherent economy by which space can be found for activities that are unlikely to be adequately addressed by conventional development scenarios.
Layers of space formerly ignored or associated with the banality of a particular engineering problem must now be reconsidered and addressed in this moment of heightened interest and investment in infrastructural upgrades and repair. By actively engaging them, such spaces can be folded into the public realm, making them at once more legible and less obtrusive to contemporary patterns of land use, transportation and culture. This strategy instrumentalizes infrastructure for public use and local benefit, not as an afterthought to private development but as an existing and potent prefigurative device for urban change.
The Culver Viaduct
In the Gowanus, what appears to many an abandoned and contaminated area standing as an impediment to economic development is in fact already teeming with activity, albeit behind closed doors and at a relatively small scale compared to the area’s more intensive industrial past. What is lacking is a coherent and legible public arena in which interaction among the diverse group of current users can occur. Indeed, while public access to the canal is no longer blocked by active industry, it will remain mostly sealed off as the estimated 12-year Superfund cleanup process begins.
The Culver Viaduct, which carries Brooklyn’s F and G subway lines over the Gowanus Canal, offers a prime opportunity to implement precisely this strategy. Given its legitimate place in local history and the public imagination, the viaduct offers an ideal armature within which to stage a new set of conditions for the broader Gowanus site, without touching the most ecologically damaged areas at all. And it happens to be currently undergoing a $300 million replacement of its concrete structural deck. What follows is Underline, my design proposal for the Culver Viaduct — an opportunistic repurposing of existing, functioning infrastructure to address the need for a vibrant and coherent public realm. Unlike the High Line and many other recent adaptive reuse projects that employ linear infrastructure as an armature, this strategy is not dependent upon the termination of active rail (or other) service in order to produce viable sites for intervention.
Site History
When completed in 1938, the Culver Viaduct was the only elevated portion of the original Independent Subway system, and reached a height of 90 feet above grade in order to accommodate tall ships on the Gowanus Canal while also supporting two above ground stations. With the canal and its banks recently designated a Federal Superfund site (in March, 2010) and now mostly unused for shipping of any kind, the extreme vertical separation of these layers can be reconsidered: the concrete structure both offers large volumes of valuable “free” space and is the threshold to contaminated ground.
Because the curving train line is not constrained to the urban grid, the structural piers transpose the geometry of the rail bed to the streets below, with columns landing on sidewalks but not the streets themselves. The result is an array of unique spatial conditions, each with a slightly different disposition relative to surrounding streets and buildings.
The structure’s dimensions, despite being highly irregular and specific to local structural demands and adjacent site constraints, are ideal for inhabitation – increments are generally between 15 and 20 feet in each axis, providing spaces of a useful scale.
Underline Section | Rendering by John McGill
The Scheme
Four types of “preservation” emerged as essential to the architectural strategy: preservation of sunlight, of structural stability, of limited footprint at ground level, and of existing (historic) character. Informed by these criteria, Underline offers four potential modes of intervention: the creation of flexible space for public assembly; precast concrete decking hung from above on steel rods as a public landscape “ribbon;” pure infill at ground level; and adaptive reuse of, or interface with, existing adjacent structures.
Sunlight animates the existing structure and is essential to the unique experience found on the sidewalks around Smith and 9th Streets. Aggressive infill of the viaduct’s undercarriage – a strategy often employed in Europe – would compromise this special quality and risk casting a shadow over any future street life. A 3D analysis of solar exposure within the space of the viaduct throughout the year revealed that despite its inherent drama at sunset, it remains dark throughout most of the day, year round.
Underline Solar Exposure Analysis | John McGill
The solar analysis led to a strategy of puncturing the deck of the viaduct strategically, cutting openings within the supporting piers and inserting steel lattice “skylights” to carry the rails overhead. Enclosed volumes of multipurpose classroom space could then be clustered below the openings, within the existing structural frames. Each volume is shaped by the angles at which the sun tends to reach the street below, so that the persistence of large areas of shadow is minimized. By night the relationship reverses: prismatic volumes glow with artificial light, projecting it into the darkness of the canal.
In order to preserve the integrity of the existing structure, asymmetrical loads would have to be avoided. We can’t assume that the existing reinforced concrete truss members are capable of carrying additional load. This means that the route of the pedestrian ribbon is largely dictated by the clearances found within and between the trusses at various heights above the street, and the places where it can be fastened to the re-engineered deck above for support. In areas where existing (but unused) playgrounds and vacant land exist beneath or adjacent to the viaduct, the landscape ribbon is free to move outboard to form the roof for new enclosed spaces below, and offers views and pedestrian access into each space. The ribbon tapers and swells as it moves through the structure, seeking light and connecting opportunistically between discreet elements of the program.
Underline Pedestrian Walkway | Rendering by John McGill
The fourth mode of intervention, adaptive reuse, occurs primarily at the concrete plant at Smith and 9th Streets, which is the only active business immediately adjacent to both the viaduct and the canal itself. Once decommissioned, the structure could be reinvented as a climbing wall – an injection of new activity to animate and preserve an evocative and representative historic structure.
Preserving this set of desirable existing conditions results in a series of distributed spaces connected by a linear public park. This establishes a sequence of unique visual experiences as one moves along, offering glimpses of unexpected adjacent activities, the regular appearance of moving trains overhead, and the rhythmic discharge and departure of passengers to and from the stations at either end of the project site — not to mention views of the city currently reserved for F and G subway riders.
Despite being distributed, however, the program is arranged in discernible clusters so that points of access to each component of the project are clearly legible from the street. Starting from the south, the first of these might contain an EPA monitoring station and public exhibition space, a café, public outdoor amphitheater, rock-climbing wall, and classrooms. The next section consists of covered outdoor basketball courts and a small public fitness center and lap pool, and in the final group retail and production spaces. Because each element is knit into the whole by the landscape ribbon, a loose affiliation emerges between both related and unrelated events in time and space.
Underline Public Amphitheater | Rendering by John McGill
The project also includes a provision for storm water collection on the surface of the rail deck, with drains feeding hanging gardens of deciduous vines suspended on wire mesh from the rods supporting the landscape ribbon, as well as the plantings along the ribbon itself. Such plants would perform in two ways – filtering and retaining storm water before it reaches the street or the canal as runoff, and filtering light during the summer to shield passersby. As a repetitive element related to the structural cadence of the existing viaduct, the hanging vines would further reinforce existing tensions between the geometry of the viaduct and the city around it.
Initially an elevated platform for public observation of a compromised landscape, this thin viaduct could eventually shed its image of forbidding overpass, under which people move by default, confined by fences and traffic, and emerge as a vital, engaging public passageway and gateway – a shift from mere edge to public threshold.
Underneath the Culver Viaduct | Photo by John McGill
