High Line

Challenge

As the High Line was neither clearly a terrestrial park, nor a building, nor a pedestrian bridge, fundamental project aspects such as the regulatory and approvals process and related agency jurisdictions were not well defined. At the time, the High Line’s location on the far west side of Manhattan meant that there was a limited user base, as the neighborhood was primarily industrial (meatpacking), with some limited nightlife options and residential properties. As a former rail line, the High Line was cut off from the street, with no street-level entrances or exits. There was a strong concern that its elevated nature would make it very difficult to find, and that going up stairs would be too much of a hindrance to potential visitors. The narrow width of 30 ft (less in certain areas) prohibited typical city park programming such as ballfields and large lawns while also making it difficult to accommodate more than one path to prevent bottlenecking for activities such as taking photos. Limited soil depth, extreme weather conditions from placement on an elevated structure, increased wind, and the expectation of future development (with unpredictable design manifestations) made creating viable plantings a challenge. Construction staging needed to accommodate the park’s location in the midst of active industry and retail operations,  narrow on-site width, limited space, and its height 30 ft above ground level.

Solution

The design team developed organizational charts to outline regulatory oversight, clarifying the need for approvals by the NYC Department of City Planning, Parks and Recreation, Transportation, Fire, and Buildings, as well as the Office of the Mayor and the Public Design Commission. By working closely with these agencies, designers confirmed jurisdictional boundaries and regulatory requirements, such as egress. They generated clear visuals and presentations, enabling them to communicate the design to each agency’s specialized interests. Furthermore, the design team hired an expeditor to advise on how to fill out permits, attend all agency meetings, capitalize on existing relationships with agency staff, and to advise on potential regulatory or permitting issues.

The challenge of user base was addressed through a two-part solution: first, by creating a compelling destination that offered unique experiences within the city instead of converting it to more of an alternative transportation route for bikes and pedestrians; and second, by developing local community outreach programs, both during design and post-occupancy, in order to gather community feedback, garner awareness and support, and create a diverse user base of not only tourists but local residents as well. Specific instances of outreach include: public meetings, one-on-one and small group meetings at the Chelsea Houses (public housing), construction initiatives, teen employment, and the FHL volunteer program.

To facilitate access, entrances are located every 2-3 blocks and correlate with bus, subway, and cross-street connections to Hudson River Park. Integrated signage on top of the High Line includes the number of the street below so that visitors are aware of their location within the city. Elevators are brightly colored and highly visible. The NYC Parks Department and the High Line’s logo and font is consistently applied to signage for recognizability.

In order to address the environmental conditions that made planting a challenge, the design team devised a broad-based strategy including using highly engineered soil to both reduce weight on the structure and hold water, selecting dry prairie species for several areas, grading hardscape toward planting beds to help limit irrigation needs, designing mounded planting areas and/or including planter edges to increase soil depth in areas for trees, and selecting plants that were adapted to both sun and shade. At the time that Section 3 was designed, the design team knew the general development massing to plan for, due to rezoning and Hudson Yards’ development as a singular coordinated project. Wind, sun, and shade pattern studies were done with the projected massing, and plants were specifically chosen and located based on future anticipated future site conditions. The planting scheme for Section 3 was specifically designed to evolve while still maintaining the core design intent, which had allowed for flexibility in swapping out certain plants that were not thriving. The limited width of the High Line offered the opportunity to create a public promenade that winds through various immersive experiences of different ecotypes and does not require normative width. Section 3 additionally incorporates alternate paths where people can walk more slowly, sit, talk, and relax.

The design and construction teams developed highly detailed construction sequences to minimize staging. All construction machinery and building materials had to be craned onto the park. For all sections, the construction process began with the rehabilitation and remediation of the structure, then site preparation of structural steel and concrete repair and lead paint abatement, followed by waterproofing and installation of drainage systems. Next, concrete planking and pre-cast furniture were installed while utilities were laid below. Stairs, elevators and additional special features were integrated into the railway structure. Lastly, the layers of the green roof system and engineered soils needed to support the plantings was placed, and tens of thousands of plants were installed.

Throughout the High Line:

• 1.45 miles of trails were incorporated on top of the former industrial railway, creating over 23 blocks of walkway unencumbered by vehicular traffic and linking the neighborhoods of Chelsea, Greenwich Village, and Midtown West. The entire park is universally accessible, including all park features. 
• There are 11 entrances to the elevated park, with 5 elevators and 1 at-grade access point. Access points are adjacent to public transportation stops with 7 bus lines, 5 subway lines, bike-sharing facilities, and bike racks all within a half-mile radius.
• Over 500 species of plants and cultivars, about 50% of which are North American native, were chosen for their hardiness, adaptability, diversity, seasonal variation, color, and texture. Over 30% of native vegetation is endemic to the NYC region planted to attract pollinator species. The High Line adds 125,640 sf (3.5 acres) of cultivated gardens to Manhattan.  
• 200 species of perennials, 40 different grasses, over 75 different bulb species, and over 150 species of trees and shrubs are planted on site.
• Each year, the park features multicultural contemporary art, exhibiting over 200 pieces created by artists from 43 countries since its opening in 2009. 
• The majority of hardscape surfaces are open-jointed, acting as pervious pavers that enhance the retention of stormwater on site by directing runoff towards planting beds, thereby reducing both irrigation needs and stormwater impact on city sewers.
• Energy-efficient LED lighting makes up 81% of the total lighting on-site. Light fixtures are positioned below the handrails, and all light is directed below eye level, illuminating pathways while reducing light pollution.
• Reclaimed wood and recycled steel are incorporated into custom furniture and decking. There are more than 230 benches and seating areas on the High Line. 

Section 1 – From south to north

• The Tiffany & Co. Foundation Overlook is a dramatic balcony which sits above Gansevoort Street, marking the point at which the High Line was severed in the 1990s when its southern portion was demolished. The Overlook provides views eastward over the industrial awnings and cobblestone streets of the Meatpacking District and westward to the Hudson River.
• At the top of the Gansevoort Stair, the Gansevoort Woodland is made up of dense plantings and a grove of gray birch and serviceberry trees. The woodland’s raised planting beds creates a greater soil depth than is found on most of the High Line. Shade-tolerant species, including redbuds, Pennsylvania sedge, and perennial bluestar thrive in the woodland, and its autumn foliage makes it one of the most picturesque spots on the High Line in September and October.
• The Washington Grasslands, between Little West 12th and 13th Streets, is the widest section of the High Line. Tall grasses, green in the early summer and golden in the fall, line the path, which passes under The Standard, a hotel that bridges over the park. Groupings of the High Line’s distinctive “peel-up” benches provide clustered seating in this section. The original railroad tracks crisscross in the planting beds.
• The High Line curves gently as it splits into 2 levels just north of 14th Street. The upper level, known as the Diller-von Furstenburg Sundeck, is lined with custom wood lounge chairs that roll on wheels along railroad tracks and receive full afternoon sun, even in the winter. In the warmer months, a thin scrim of continuously recycled water skims the surface of the western side of the path, buffering noise from the West Side Highway and allowing visitors to wade barefoot and referencing the Hudson River, which is at its nearest here. Along the lower level, railroad tracks were reinstalled in plantings derived from the High Line’s self-sown landscape. 
• At West 15th Street, the High Line enters the Chelsea Market Passage, a semi-enclosed former loading dock space for what was once an industrial bakery for the National Biscuit Company, also known as Nabisco. The building was converted for public use as Chelsea Market in the 1990s. This semi-enclosed passage has an upper and lower level to provide a city-block-long refuge on hot summer days. On the lower level, the High Line Porch provides café seating. 
• The Northern Spur Preserve evokes the wild landscape that grew on the High Line before it was a park, featuring crabapples, asters, sedges, catmint, and phlox. Visitors cannot enter the section, but instead view it from the observation deck above the preserve.
• Hundreds of tons of steel suspended above a busy avenue make up the High Line’s most monumental feature, the Tenth Avenue Square. As part of the High Line’s transformation into a park, the steel beams of the square’s upper deck were removed to make way for wooden steps and ramps, creating an amphitheater-like space that allows visitors to inhabit the structure. The southwest side of the Tenth Avenue Square hosts a grove of three-flowered maples, establishing a shaded seating area and offering views south across the Hudson River to the Statue of Liberty.
• North of West 17th Street, the High Line sweeps gently toward the Hudson River and begins a mile-long straightaway north through Chelsea. Inspired by the self-sown landscape that grew on the High Line when the trains stopped running, the Chelsea Grasslands is planted with wild grasses and wildflowers that add color and texture throughout the four seasons. This section also gives visitors a unique perspective on the old and new architecture of the neighborhood. Between West 18th and West 19th Street, new buildings designed by leading architects are juxtaposed with the industrial brick architecture of the neighborhood’s older factories and warehouses.

Section 2 – from south to north

• As the High Line continues north from the Chelsea Grasslands’ prairie-like landscape, a dense planting of flowering shrubs and small trees indicates the beginning of Section 2 of the park between West 20th and West 22nd Streets. In the Chelsea Thicket, species like winterberry, gray birch, and large American hollies provide year-round textural and color variation. This is the deepest soil placement on the High Line without planters – soil depths are up to 36 in, while an additional under-planting of low grasses, sedges, and shade-tolerant perennials further emphasizes the transition from grassland to thicket.
• The High Line widens between West 22nd and West 23rd Streets, where an additional pair of rail tracks once served the loading docks of adjacent warehouses. The extra width in this area was used to create a gathering space, with Seating Steps made of reclaimed teak anchoring the southern end of a 4,900-sf lawn. At its northern end, the Lawn rises several feet into the air and creates views of Brooklyn to the east and the Hudson River and New Jersey to the west.
• Between West 25th and West 26th Streets, adjacent buildings create a microclimate that once supported a dense grove of tall shrubs and trees. Now, the Philip A. and Lisa Maria Falcone Flyover, a metal walkway rising 8 ft above the High Line, rises above groundcover plants on the undulating terrain below and leads visitors upward into a canopy of sassafras and magnolia trees. At various points, tangential overlooks branch off the walkway, creating an immersive environment with views of the plantings below and the city beyond.
• Hovering above the historic rail on the east side of the High Line at West 26th Street, the Viewing Spur’s frame is meant to recall the billboards that were once attached to the High Line. Now the frame enhances, rather than blocks, views of the city. Tall shrubs and trees flank the Viewing Spur’s frame, while a platform with wooden benches provides a space to view 10th Avenue and Chelsea.
• Between West 26th and West 29th Streets, the Wildflower Field is dominated by hardy, drought-resistance grasses and wildflowers and features a mix of species that ensures variation in blooms throughout the growing season. The simplicity of the straight walkway running alongside the wildflowers interspersed between the original railroad tracks highlights the green axis of the High Line as it moves through the city.
• At West 29th Street, the High Line begins a long, gentle curve toward the Hudson River, signifying a transition to the West Side Rail Yards. The High Line’s pathway echoes the curve, and a long bank of wooden benches sweep westward along the edge of the pathway forming the Radial Bench. Planting beds behind and in front of the benches line the curve with grasses and perennials.

Section 3 – From east to west

• The Rail Track Walk consists of 3 linear walks located in different areas along the High Line at the Rail Yards. They expose the High Line’s historic rail tracks, evoking the space’s history as an active freight rail line. On these walks, visitors can interact with artifacts such as the rail “frog” and rail switches or rest in one of several alcove pockets of peel-up benches located throughout the pathways. Planting beds featuring a naturalistic landscape border the pathways.
• As the High Line runs west over 11th Avenue, the main pathway gradually slopes up about 2 ft, creating an elevated catwalk over the avenue known as the 11th Avenue Bridge with views of the park, the city, and the Hudson River. Lush display gardens on either side of the catwalk separate the main pathway from the more intimate linear bench seating running along the railing on either side.
• Just west of 11th Avenue is a unique design feature for children, the Pershing Square Beams. Here the High Line’s concrete deck is stripped away, revealing the original framework of steel beams and girders. The structure itself is transformed into a series of sunken areas – coated in a silicone surface for safety – in which children can run, climb, and play. The area also includes a series of play elements developed exclusively for the High Line, such as a rotating beam, periscopes, a gopher hole, and talking and viewing tubes.
• At the park’s northernmost point is the Interim Walkway, which features a simple path through the existing self-seeded plantings and 4 gathering spaces.The interim walkway is designed as a temporary feature of a section that is still to be redeveloped and does not include lighting. This area of the High Line will undergo complete renovation and remediation following an additional capital campaign and the completion of Hudson Yards.

Friends of the High Line
In 1999, the Friends of the High Line (FHL) was formed by two local residents to save the High Line from demolition and transform it into a public park. Today, the nonprofit conservancy employs over 100 full-time employees with an organizational mission “to engage the vibrant and diverse community on and around the High Line through excellence in operations, stewardship, innovative programming, and world-class design and to raise the essential private funding to help complete the High Line’s construction and create an endowment for its future operations.”

Public-Private Partnership
At the time of its inception, there were few examples of public-private partnerships engaged in the acquisition, design, construction, funding, and operations of public parks. The client for the High Line is the public-private partnership between the City of New York and FHL. The city entities associated with the High Line are the NYC Department of Parks and Recreation, the Office of the Deputy Mayor for Economic Development, the NYC Economic Development Corporation, and the NYC Department of City Planning. While the City of New York owns the High Line, FHL maintains and operates the park, has raised nearly $135 million for the capital costs of the park, and raises nearly 100% of the annual operating costs. 

Sustainable Practices
Friends of the High Line works to maintain the park by integrating sustainable practices into its day-to-day operations. An elevated park poses several challenges due to limitations on space, with both the operations and horticulture teams constantly innovating for the most efficient ways to compost plant debris, recycle, and remove trash. The Horticulture department composts nearly 100% of plant material on-site, in addition to brewing compost tea (800 gallons were applied to the park soil in 2016) and testing soil quality on site. All compost is recycled back into the garden beds. The gardeners utilize an integrated pest management approach, mechanically removing pests to maintain plant health and introducing beneficial organisms as needed. Over the course of a typical season, 1,260,000 Lacewings are released as a control for leafhoppers, lace bugs, and aphids. In addition, 6.75 billion nematodes are released into the soil as a control for white grubs. These practices eliminate the use of chemicals in the landscape and allow for a greater diversity of organisms to thrive – protecting human health, the resiliency of the soil and the ecosystem as a whole. New plant material is sourced locally and sustainably, with some plants propagated in the staging areas of the High Line itself. In the winter, snow removal is done by hand or with brush attachments to small vehicles, eliminating salt and other harmful chemicals and increasing the longevity of paving materials in the park.

• Demolition and removal of the structure was estimated to cost $27 million. However, removal of the High Line’s structure would have negated the city’s prior investment in its original use as a transportation project that cost the city $125 million in 1930, the equivalent of $1 billion in 2002.
• Repurposing the High Line was predicted to provide tax revenue to the City of New York equal to 200-300% of the estimated capital costs of $65 million. As of 2018, while the city’s investment in the High Line is closer to $140 million, the incremental tax revenue for the city is closer to $1.4 billion, more than 900% of the capital costs.

• The High Line illustrates the power of well-designed public space to attract visitors. Furthermore, it has inspired many cities to re-look at their unused or abandoned structures and adapt them as public space instead of demolishing or privately developing them. Friends of the High Line has devised a peer-to-peer group of infrastructure reuse projects designated as the High Line Network to advise and support other grassroots public realm projects. 
• The High Line displays the critical importance of a strong and enabled client to support a bold design vision, guide the project through regulatory and administrative hurdles, raise funds and garner public support, and then finally to care for the park and ensure its long-term success. 
• While some planted areas of the High Line experience damage from sun scorch and wind due to the changing built context, overall, the plants are much larger and healthier than had been anticipated, especially considering the typical shallow planting depths of 18 to 24 in. The planting has become a major draw for visitors, and is listed in the top three reasons for visiting per the FHL Visitors Study. While peak visitation is May through October, the park is used year-round, and many who visit in the late fall, winter, and early spring come to see the seasonal landscape variation. With its high level of biodiversity, the plantings have captured the public imagination, with several lectures and publications focusing solely on the subject.

Soils: The Dirt Company
Custom precast planks: Designed by James Corner Field Operations and Diller Scofidio + Renfro, made by BPDL
Bonded Aggregate: Soleco
Metal Grating: Ohio Grating
Lighting: I2 systems; BK- lighting; GE lighting solutions; Technilum
Furniture: James Corner Field Operations and Diller Scofidio + Renfro
Fences/Gates/Walls: James Corner Field Operations and Diller Scofidio + Renfro
Irrigation: Charter Plastics; Paige Grounding Systems; Pentek Boxes; Apollo Valves; Rainbird Sensors; Netafim
Lumber/Decking/Edging: Sawkill Lumber; East Teak Lumber
Recreation Equipment: James Corner Field Operations and Diller Scofidio + Renfro
Elevators: James Corner Field Operations and Diller Scofidio + Renfro; IRIS Elevators
Stairs: James Corner Field Operations and Diller Scofidio + Renfro
Green Roofs/Living Walls: Zinco
Signage: Designed by Pentagram; James Corner Field Operations and Diller Scofidio + Renfro, built and installed by Winsor Fireform

Project Team

Official Project Credit: James Corner Field Operations (project lead); Diller Scofidio + Renfro; Piet Oudolf 

Core Specialists (all sections)
Structural/MEP Engineering/Life Safety Engineering: Buro Happold
Structural Engineering/Historic Preservation: Robert Silman Associates
Lighting: L’Observatoire International
International Signage, Identity, and Wayfinding: Pentagram Design, Inc.
Irrigation: Northern Designs Civil and Traffic
Engineering: Philip Habib & Associates

Section 1 Specialty Consultants 
Soil Science: Pine & Swallow Associates, Inc.
Environmental Engineering: GRB Services, Inc.
Cost Estimating: VJ Associates
Code Consultant: Code Consultants Professional Engineers
Water Feature Engineering: CMS Collaborative
Public Space Management: ETM Associates
Surveying: Control Point Associates, Inc.
Expediting: Municipal Expediting Inc.
Technical Specifications: Paul DiBona Specifications LLC
Resident Engineer: LiRo/Daniel Frankfurt
Landscape Construction Management: SiteWorks
Community Liaison: Helen Neuhaus & Associates
General Contractor: KiSKA Construction
Construction Management: Bovis Lend Lease

Section 2 Specialty Consultants
Environmental Engineering/Site Remediation: GRB Services, Inc.
Soil Science: Pine & Swallow Associates, Inc.
Public Space Management: ETM Associates
Cost Estimating: VJ Associates
Code Consulting: Code Consultants Professional Engineers
Surveying: Control Point Associates, Inc.
Expediting: KM Associates
Resident Engineer: HDR + LiRo
Landscape Construction Management: SiteWorks
General Contractor: CAC
Community Liaison: Helen Neuhaus & Associates
Construction Management: Bovis Lend Lease

Section 3 Specialty Consultants
Play Safety Consultant: Site Masters Inc.
Environmental Consulting: Roux Associates, Inc.
Elevator Consultant: IRIS Elevators
Soil Science: Craul Land Scientists, Inc.
Security Design: MKJ Communications
Cost Estimating: Dharam Lally & Smith
Building Code Consultant, Expediting: JAM Consultants Inc.
Site Surveyor: Control Point Associates, Inc.
Construction Manager, Landscape Design: Sciame
Construction Manager, Site Preparation: LiRo
Subcontractors: BPDL, CAC, Concrete Industries One, Steven Dubner Landscaping, Egg, L&L Painting, Sunny Border, Venture, FMB, Sawkill Lumber, Site Works, ATTA Inc., Landscape Structures, Studio dell’ Arte, Optical Mechanics Inc. VGS

Role of the Landscape Architect

The Landscape Architect/Project Lead led the overall design concepts and design development throughout the project; worked closely with the City of New York and Friends of the High Line to deliver a holistic, implementable design; led the large, multi-disciplinary team; led the agency approvals strategy; provided overall project management from design through construction; provided full landscape architecture services from Schematic Design through Construction Administration, including planting, paving, furnishing, and layout; and led public engagement and construction processes.