A landscape architect’s most transformative space-making tool is grading. Grading is used functionally to channel run-off and provide adequate drainage. Beyond the purely functional, however, grading creates heaving bulges and recesses, small dips and peaks, and swaths of smooth, flat areas for an unfolding, undulating sequence of spaces.
Manipulating topography is a powerful way to create small and large scaled spaces, conceal and reveal vistas, suggest intimate areas, and shape the ‘ah-ha’ moments in the park and public spaces. Sculpted topography works in concert with pathways and trees to choreograph the park experience. It maximizes the sense of anticipation, pulling a visitor through the park or signaling a place to sit and stay in one place just a bit longer. It defines the very character of the areas of the park.
Reshaping and engineering the landscape is a fundamental strategy of the Master Plan. The major re-grading begins just south of Liggett Terrace. Here, in the Hammock Grove, fill is added to build a higher woodland “threshold” masking views of the spaces beyond. Moving southward through the Hammock Grove, visitors emerge and traverse the gentle grading of the open Play Lawn. At the Play Lawn, the land drops imperceptibly on its western edge to bring people to the public plaza at Liberty Terrace, which sits along the water’s edge.
On the other side of the Play Lawn, its rolling grass rises to form the lower reaches of the Hills. The Hills themselves are the most dramatic form of the re-sculpted land. Across the southern half of the Island, grading is used to define the various areas and smoothly transition from one to the next. At the South Prow, the Hills frame the low-lying Wetland Gardens and set them off in dialogue with the wide expanse of New York Harbor.
The West 8 Team suggested the creation of a vertical landscape as the central concept in their competition entry, articulating the Hills’ potential for an unparalleled view and transformative landscape. Throughout the Park and Public Space Master Plan design process, there has been extraordinary rigor in validating that this concept could be developed into a real landscape which meets standards for landscape design, visitor experience, construction, creation of habitat and maintenance.
The conceptual design of the Hills was developed in concert with the team’s engineering consultants, ARUP. Working together, the West 8 Team determined feasible ways of building the Hills using standard engineering methods.
They concluded that building requires a “pre-loading” construction phase where weight from fill is applied to the hill areas so that the earth beneath stabilizes and drains out trapped water over time, approximately 18 months. The engineers and designers worked in concert with cost estimators to ensure that the phasing and overall topography plan fit within the project budget.
The Hills are engineered using construction methods keyed to three different grades. Hill grade is measured in terms of a ratio of the vertical rise to the horizontal run. An area where the elevation rises by one foot as you move three feet across has a ratio of 1:3 (also described as a 33% slope), and an area where the elevation rises by one foot as you move one foot across has a ratio of 1:1 (also described as a 45% slope).
For areas where the side slopes have a ratio of 1 (vertical) to 3 (horizontal) or flatter, reinforced earth is not required. The slope is conventional fill embankment using common borrow or cement-treated dredge material. The fill is compacted in layers and top dressed with topsoil.
Construction Methods for Slopes
Where the hill slopes are between 1 (vertical) to 3 (horizontal) and 1 (vertical) to 1 (horizontal) the mounds are constructed around a core of recycled demolition material and dredged material. This core is then surrounded by a reinforced earth slope of select granular fill. The two fill zones are separated by geotextile (permeable fabric) mats. Bi-axial and uni-axial grid reinforcement are embedded within. Topsoil is placed over the granular fill and turf reinforced sod matting is installed to protect plantings.
For slopes at 1 (vertical) to 1 (horizontal) or steeper (up to 70°), the hill sections are constructed out of a series of reinforced earth walls and reinforced sloped embankment at a ratio of 1 (vertical) to 3 (horizontal). This creates a terrace effect at the steepest slope sections. This construction requires three different fill materials with separation geotextile laid at each interface.
Recycled building demolition material and dredged material form the core, surrounded by select granular fill material. Outside the core, the wall facing can have a variety of finish treatments. It can be exposed and sculpted masonry or concrete or it can be planted. A planted facing consists of wire baskets filled with two to four-inch stone covered with galvanized welded wire faces. The face is then prepared with a turf mat and planted to conceal the wire basket structures
The design of the Hills evolved throughout the master planning process, in parallel with understanding of the engineering, fill and materials required. Hill locations were shifted. The team worked out the accessibility of pathways. Each hill was shaped and re-shaped to make it an enjoyable place to be, to frame views, and to maximize views from the top. Forms and slopes were adjusted to make the Hills a more productive habitat and better growing medium for vegetation ranging from ground covers to large trees. Each hill is asymmetrical with one steeper face and other shallower faces. These are sculpted in relationship to each other.
SECTIONS OF THE GREAT PROMENADE
The South Prow Overlook and a stretch of the western Promenade will be elevated seven feet above the existing grade. This strategy, using fill material, creates two parallel pathways, one lower and one higher. Raising the Great Promenade has many benefits:
• It increases the locations and variety of view points — just a seven-foot elevation creates a different perspective on the Harbor than the view from the same spot at grade.
• It creates areas for seating and separates pedestrians from bicycles in an area where people are likely to linger and enjoy the views.
• By raising the grade, trees planted on the upper level will have their roots lifted above the future flood elevation level, ensuring decades of growth and shade.
“The Way it Works” explains how the elements of the park and public space function. While the design is at the master plan stage, considerable work underlies the plan to ensure a strong foundation for future implementation. The West 8…
The program brief for the park and public space is based on a number of key principles:
• To provide unique experiences that capitalize on the attributes of the Island and its harbor location
• To create a destination that…
Parks are more pleasurable and more memorable if they have a rich layering of spatial qualities. The new topography at the southern portion of Governors Island cultivates the views of the Harbor. The park and public spaces will be designed…
Clear, organized circulation is essential to the legibility of the park and public spaces and to the safety of users. A network of pathways and roads serves pedestrians, bicyclists, and service vehicles, with a hierarchy of path uses and path…
There is a conscious effort to correlate paving treatments and expression to the character of different park and public space areas and experiences. The horizontal plane underfoot (or under bicycle tires) contributes significantly to the experience.
Stretches of path and…
Edging is another key element of the Park and Public Space Master Plan. Edging surrounds and defines the perimeters of lawn and planted areas and the “pillow-shaped” topography. Edging serves multiple functions: clarifying paths, guiding bicyclists, and retaining grade. Its…
Seating, lighting and other furnishings are critical to the visitor’s experience of any public space or park. An array of well-designed and well-located furnishings makes for a comfortable and inviting experience. Furnishings help establish character and feel. They also must…
The Historic District’s protected conditions, higher elevations and quality top soils make for ideal conditions to grow large, beautiful shade trees and support other plantings. On the southern half of the Island, poor quality soil, exposure to harsh salty winds,…
The Park and Public Space Master Plan includes conceptual-level designs for three buildings to serve visitors and their needs for rest, refreshment, and information: Soissons Ferry Pavilion, the Shell at Liberty Terrace, and the Cube at Yankee Landing.