We like to think of the High Line as a mile-and-a-half-long recycling project. A former industrial structure given new life as a public green space, the High Line takes the idea of reuse to another level.
Wherever possible in the planning, design, construction, and operations of the High Line, Friends of the High Line and the Parks Department strive to make sustainable choices. Beyond the scope of the High Line itself, we believe the project can serve as a model for adaptive reuse and sustainable practices for parks and planning projects around the world.
Design and Construction: The World's Longest Green Roof
The High Line's landscape uses the same technology as a green roof, and has the same environmental benefits: a reduction of storm-water runoff by up to 80%; a mediation of the "Heat Island" effect created by hard, reflective city surfaces; and plantings that create shade, oxygen, and habitat for insects and birds.
The High Line's "Living Roof" system, set atop the waterproofed concrete of the structure itself, is made of several layers:
- A perforated black plastic "egg-crate" drainage panel to provide water retention, drainage, and aeration to the soil
- A layer of crushed pea-gravel to act as a buffer, regulating the speed at which water drains
- Woven filter fabric to keeps soil particles from clogging the drains
- A layer of coarser, clay-based subsoil
- A layer of finer, more nutrient-rich topsoil
- A top layer of gravel mulch to aid in water retention and prevent soil erosion due to wind
Drainage: The High Line's pathway system was designed both to reduce storm water runoff and to reduce the amount of water brought in for the plants. The paths are made of open-jointed concrete planks allowing rain water to drain between planks and into adjacent planting beds. Strategic location of the drains at low points in the planting beds maximizes water flow through the beds, reducing the amount of runoff.
Materials: All materials brought in for the High Line landscape—the concrete in the planks, steel, wood, and other materials were selected based on life-cycle costs to reduce the need to replace and dispose of materials after a short time. The wood used on the High Line is an FSC-certified ipe hardwood, sustainably harvested from a managed forest, selected for it durability and reputed life-span of up to 100 years.
Lighting: The High Line's innovative lighting system uses energy-efficient LED lights to safely illuminate the pathways and plantings without causing overhead glare or wasting energy.
Water Feature: The water feature on the High Line's Diller – von Furstenberg Sundeck uses a closed-circulation system, which reduces the amount of water used in the feature.
Greening the High Line: Plant Selection and Sustainability
The High Line's unique landscape was created in partnership with Netherlands-based planting designer Piet Oudolf. For inspiration, Oudolf looked to the existing landscape that grew on the High Line after the trains stopped running. The plant selection focuses on native, drought-tolerant, and low-maintenance species, cutting down on the resources that go into the landscape.
Site-Specific Landscape: Varied conditions of light, shade, exposure, wind, and soil depth on the High Line in its out-of-use state led to an incredibly complex variety of growing conditions, or "micro-climates". The original, self-seeded landscape reflected this variation – where the High Line was narrow and sheltered by adjacent buildings, water was retained, soil was deeper, and vegetation was thicker, including several groves of tall shrubs and trees. Where the High Line was exposed to winds off the Hudson, the landscape was dominated by several varieties of tough, drought-resistant grasses and wildflowers.
The current park landscape was created to reflect the original micro-climates on the High Line. By basing the planting design on naturally-created plant communities, we create a well-adapted, site-specific landscape, cutting down on water and other resources needed to maintain it.
Local Sourcing: Most of the High Line’s plants are native species, and many were produced by local growers. Locally-grown plants are better adapted to grow successfully in our climate, reducing the amount of plant failure and replacement costs. The High Line’s ecosystem provides food and shelter for a variety of wildlife species including native pollinators. Whenever possible, we source materials within a 100-mile radius, including some plants from the New York City Parks Department’s Greenbelt Native Plant Center.
A Commitment to Sustainable Operations
Equally important to the High Line’s design is the way in which it is maintained and operated on an ongoing basis. In all of our operations, we strive towards sustainability with the same level of care that went into the park's design.
Watering: In addition to rainwater runoff (see "drainage" section, above), we provide supplementary watering as needed. Though drip irrigation is used on specific sites on the High Line (largely where our young groves of trees require a more consistent water source in the summer), the landscape relies for the most part on hand-watering. This way, our gardeners are able to tailor the amount of water based on the needs of individual species and weather conditions, and conserve water. Many of the plants are drought-tolerant and once established will only need supplemental watering in the cases of drought.
Composting: We are in the process of establishing on-site composting facilities that will be able to recycle our garden waste into compost. We are exploring the possibility of partnering with local businesses to compost their food waste to reduce the amount of compostable material entering the waste stream.
Pesticides: The High Line does not use pesticides or chemical fertilizers. Through sound horticultural practices and using well-adapted plants, the need for using pesticides and chemical fertilizers is reduced. We are in the process of developing an Integrated Pest Management program to sustainably address any issues dealing with potential pests and diseases. The compost produced on-site will provide the nutrients necessary for healthy plant growth. Healthy plants are found to be much more resistant to pest and diseases than plants that are ill-adapted or stressed.
Solvents, Cleaners, and Other Chemicals: The High Line promotes environmentally-sound purchasing through the use of Green Seal-certified cleaning solutions and post-consumer paper products for our recurring maintenance needs.
Snow Removal: On the High Line, we drastically reduce the dependence on the use of rock salt or chemicals to melt snow and ice by relying on manual methods of snow and ice removal. We create a safe walking path by removing snow with a power broom wherever possible, and hand-shoveling when necessary. If needed, we apply an eco-friendly ice melting product that is safe for the plants and environment.