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04-12-21 | Department

Historic Rooftop Plaza Redesigned

Mellon Square, Pittsburgh, PA
by Patricia O'Donnell, Heritage Landscapes LLC

Landscape Architects with Heritage Landscape LLC led efforts to preserve and redesign Mellon Square, a rooftop garden that was initially constructed in 1955 in Pittsburgh, Pennsylvania. Mellon Square shines at night with fountain and planter lighting as well as 'moonlight' illumination from the top of the adjacent hotel. Photo: Courtesy Pittsburgh Parks Conservancy
Distinctive rough terrazzo paving brings a unique visual and tactile quality to the 5% sloped pavements. Texture employs four white, black, gray, and green tones of mortar, and four colors of marble chips, separated by metal strips over a concrete base. Mortar and marble samples and mock-ups guided the widespread repair and replacement. Photo: Heritage Landscapes, Jim Donovan
Distinctive rough terrazzo paving brings a unique visual and tactile quality to the 5% sloped pavements. Texture employs four white, black, gray, and green tones of mortar, and four colors of marble chips, separated by metal strips over a concrete base. Mortar and marble samples and mock-ups guided the widespread repair and replacement. Photo: Heritage Landscapes, Jim Donovan
Only the top of the railing is illuminated, keeping the stainless-steel mesh as transparent as possible. Photo: Heritage Landscapes

Mellon Square, a modern garden plaza and early green roof atop a parking garage, was designed from the late 1940s through 1955 as a part of the first Pittsburgh renaissance by distinguished Landscape Architects, John O. Simonds and Paul Simonds of Simonds & Simonds. The 1955 public opening celebrated Pittsburgh's first renaissance to rebrand the gritty city as a place of commerce and innovation underpinned by civic assets. This square, flanked by new mid-1950s towers for Alcoa and US Steel, provided a clear symbol of innovation and civic care.

To address Mellon Square's 21st century revitalization, the Pittsburgh Parks Conservancy sought consultants and partners, selecting landscape architecture firm Heritage Landscapes LLC and working closely with the Pittsburgh Parking Authority, Parks Department, Downtown Partnership, and local foundations as well as public funders. Heritage Landscapes' office led a diverse team to develop the award-winning Mellon Square Preservation, Interpretation & Management Plan. They went on to assemble a construction team to address preservation, reconstruction and new design to revitalize this urban gem. Research yielded a wealth of sources: design studies; photos; memos; and 1955 and 1987 construction details. Field reconnaissance recorded vegetation and built elements and mapped user behaviors.

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Analysis revealed the obvious and subtle relationships of design intent and current character noting compromises in recent decades that diminished this modern masterwork. In particular, city-driven design changes in the 1980s removed the original fountain and replaced it with a hard edge, dark fountain seating wall and removed a planter to insert a small stage for music performance. Additionally, the planter overlooking Smithfield Street was leaking into the shops below, plantings had failed, and litter including drug use paraphernalia was present.

The main fountain and cascade required reconstruction to return the lively flowing water to the square. Removing the granite-edged fountain side walls revealed the electrical, water supply, and drainage openings that were to be reused. The main fountain, a rectangle of 45' by 68', extended above the paving with a 7" cantilever at 16" above grade. This floating effect was recaptured by using 5,000 psi fiber reinforced concrete. This complex pour included recasting concrete columns for setting of the nine heavy, 5' diameter bronze basins, lighting sleeves, and water lines and fountain fittings. Recalling that the 1955 buff, green and light blue fountain tiles failed immediately, it made sense to use a simple light green waterproof coat.
The adjacent towers made viewing the plaza from above an important aspect of the design with a triangular pattern of four colors employed. This innovative rustic terrazzo paving, designed by Paul Simonds working with local craftsmen at Patrizio Mosaic, characterizes this distinctive harlequin pattern paving with high slip resistance.

The area poised weight load challenges as well as waterproofing issues. Cutting through a long planter, at specific locations to avoid apparent gaps, an accessible double ramp paved in dark gray rustic terrazzo, edged with stainless steel handrails, created an approach sequence and provided a place to stop and look. The custom outer railing, designed for leaning on and looking over the street and cascade, employs a curved, interior lit top rail and a woven wire mesh. Downlight flickers on the mesh fabric. Night lighting throughout the square, for planter walls, side walls, and steps, was technically upgraded for durability while achieving original designed effects. Restored fountain lighting includes choreography sequences.

Plaza and civic gathering place, the revitalized Mellon Square receives high daily use, expressing community appreciation. The $7M project is underpinned with a nearly $4M management endowment. This valued public space, one year after construction, helped contribute to more than $300 million in surrounding investment. Awards for the planning report and project signal the success of this important work revitalizing a Modernist masterpiece.

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