Rising sea levels, irregular weather patterns, and increasing storm surges impose enormous costs on the public and private sectors. Of the estimated $33 billion in damages in the state of New York caused by Hurricane Sandy, more than $19 billion was suffered in New York City, according to global reinsurance firm Aon Benfield, and the city alone received $13.6 billion in recovery assistance from the Federal Emergency Management Agency (FEMA) between 2012 and 2014.
Independent of any potential new projects to retrofit coastal cities, the last comprehensive report by the American Society of Civil Engineers (ASCE) estimated in 2013 that to remedy the existing infrastructure deficit alone would require investment of over $3.6 trillion by 2020. Therefore, it is unrealistic to expect public expenditures to save urban waterfronts by building massive new levee systems, like those in New Orleans, or by elevating entire districts, as Chicago did in the 1850s.
Now, in a concept generated for the Living with Water competition— held by the city of Boston, the Boston Redevelopment Authority (BRA), the Boston Harbor Association, and the Boston Society of Architects—a team of architects at Boston-based Utile has proposed a different solution for an 89-acre (36 ha) segment of the city’s industrial waterfront called the 100-Acres district.
The 100-Acres district is a classic example of tidelands filled for industrial uses and now increasingly in danger of being reclaimed by the water the fill was meant to displace. The site is largely undeveloped, and Summer Street, the main north–south connection to the heart of downtown Boston, has
already been raised to 28.5 feet (8.7 m) above sea level to span the rail lines to the east. Also, the 2.2 million-square-foot (204,000 sq m) Boston Convention and Exhibition Center, already at the 28.5-foot (8.7 m) elevation, is expanding by 1.3 million square feet (121,000 sq m) just to the east.
Linked, but Self-Sufficient
The traditional pattern of urban development creates a gridded network of public streets containing a variety of public infrastructure,
often installed below street grade and including water, sewer, power, natural gas, and telecommunications cable lines, in addition to traffic and transit systems and pedestrian and bicycle circulation paths. But with sea levels anticipated to rise through the century, storm surges and daily tidal shifts will put some portions of many waterfront sites under water and will leave most of those utilities and services unusable and residents isolated. The economic and urban value of land and buildings, and thus the tax base, could be reduced permanently.
The Utile team offers an alternative to raising an existing system of streets, including the network of public utilities and services (with privately owned blocks at the center of this complicated system). Instead, the Utile team—led by Elizabeth Christoforetti and Matthew Littell, with landscape and engineering firms Atelier Dreiseitl and BuroHappold and consultant Lambert Advisory—proposes a phased strategy of linking new, mostly self-sufficient blocks into a smaller, urban network, elevated above anticipated water levels.
The network’s resilience—and urbanity—would increase with each new building connected to it. Instead of the existing model of a distant central plant, such as a power plant or water distribution facility, dispersing services through a treelike hierarchy of lines radiating from the center, the new inverse model is analogous to the internet, in which each additional self-sufficient computer connected to it increases the network’s resilience to district outages.
So, for example, if a building produces its own power and heat from a solar array, an internal microturbine, or a fuel cell, when that building is connected in a ring with those systems in other buildings, excess supply in one building can meet excess demand in another. But each building remains self-sufficient. Distributed generation by building—rather than from distant power plant—connected by alternative looped feeds with smart switches that automatically isolate problem areas and balance load demands can create a more resilient power grid.
While it is possible in Utile’s concept to include a cogeneration plant—a facility that recaptures heat that is a byproduct of on-site energy production—on a districtwide basis, the essential concept is to decentralize production to provide resilience. Recapturing heat through cogeneration—as well as reducing losses during transmission thanks to on-site generation—increases energy efficiency by as much as two-thirds. Also, on-site water and electricity storage, the latter through batteries, can supplement water and power supplies within the network.
Telecommunications networks can be wireless systems or be connected using fiber-optic lines along multipurpose slender elevated street bridges. Because they are pressurized, water supply systems from central sources may also be run along those bridges and supplemented with on-site storage through water towers and cisterns, which were in common use a century ago.
Because public sewerage systems depend on gravity to flow, disposing of effluent in high-water conditions becomes risky or impracticable, and sloping such sewer lines, or relying on sewage pumping, diminishes the system’s resilience. Protection against siphoning of sewage during high-water conditions will be important. As underground sewerage systems dependent upon gravity flow become inundated, alternative on-site sewage treatment would be needed.
Decentralized sewage-treatment systems add cost, but their use is not unprecedented. On-site bioreactor package plants—small sewage treatment plants using membrane technology—can process blackwater and graywater for nonpotable uses, as was done at the Oregon Health Sciences University’s Center for Health & Healing in Portland. The Gates Foundation recently demonstrated an on-site sewage treatment device called the Omniprocessor, designed and built by Seattle-based engineering firm Janicki Bioenergy, which incinerates feces to power a steam engine, producing electricity and potable water as byproducts. Though designed for use in the developing world, one day some versions might be used to power buildings anywhere.
How can it be economically feasible to build such an inverse, linked building network? Development economics for such a plan are challenging even in cities where property values are high. But, compared with elevating a traditional urban grid, phasing a smaller-scaled, supplementary elevated network that connects block centers with slender elevated street bridges would be significantly more cost-effective.
The essence of Utile’s new urban block morphology creates a new set of shared spaces in the private/ public realm in elevated courtyards at the center of each block rather than at the periphery. These spaces are interlinked gradually into a networked public-space grid that is above grade—and above flood level.
An example shows how the inverse linked building network strategy is far more economical than the traditional urban grid. An average 250-by-250-foot (76 by 76 m) city block, with a 60-foot (18 m) right-of-way including sidewalks—as is assumed by the Utile team—would require 1,240 lineal feet (378 m) of streets for each block. In contrast, linking buildings across the right-of-way requires only 60 lineal feet (18 m) of multipurpose bridges—a mere 4.8 percent of the space required by the conventional peripheral street block.
Utile proposes north–south bridges connecting buildings that are 42 feet (12.8 m) wide and flanked by walkways. At that size, the 2,520 square feet (234 sq m) of a single public bridge linking the buildings is only 3.4 percent of the 74,400 square feet (7,000 sq m) of a lower street grid. For four bridges, the area is still less than 14 percent of the street grid. Utile thinks the local east–west connections can be one-way and could even be as narrow as 25 feet (8 m), reducing public cost. Internal courtyards measuring 120 by 120 feet (37 by 37 m) would be only about 20 percent of the traditional street grid.
Utile expects that block dimensions would be fixed in the north–south direction but that they might remain flexible parallel to the east–west streets to allow for a range of building types and uses and corresponding structure depths. However, because blocks will last longer than particular buildings, a more universal block pattern would offer the greatest flexibility to adapt to uses over periods as long as the century for which Utile plans.
The Public Realm
As conceived by Utile, the inverse linked building network strategy would not destroy the public realm of traditional gridded streets, though relocating circulation to a first level at least 20 feet (6 m) above grade becomes a central planning and design challenge.
Utile envisions buildings not as isolated monolithic objects, but as variegated enclosures built around common courtyards through which the public circulates. Shared streets may go around or through the courtyards that, when connected, would constitute a network of diverse urban plazas. Space that traditionally has been private would become the heart of the shared public realm. Open space, which under the traditional model is external to a building, becomes integrated throughout it. Trees growing at grade could penetrate into open courtyards and let light filter down through courtyards to tall spaces below.
An elevated neighborhood of blocks around courtyards can emerge with multitiered open spaces—new, soft tidal marshes at the water’s edge, floodable spaces occupying former road networks, and elevated hardscapes used for pedestrian connectivity, commerce, and community.
The inverted block structure could increase the income stream from buildings developed within it and facilitate leasing. Buildings could connect above the elevated circulation plane, increasing leasable space. Moreover, especially in urban fringe areas converting from industrial to urban uses, there often are not enough retail tenants to occupy all the ground-level space surrounding entire blocks. As the scale of retail companies and supply systems has changed, the amount of retail space created by traditional retail grids is now vastly larger than what existing retailers can fill, especially the smaller retailers sought by new urbanists.
Concentrating retail space around courtyards focuses activity there while leaving peripheral space available for other, more profitable uses, such as office and residential space, which do not work well at grade. In a typical 250-foot-square block (76 m), there would likely be no more than 240 lineal feet (73 m) of retail space, compared with 1,000 lineal feet (305 m) of peripheral space. Because buildings are valued as the capitalized value of their income streams, building capital values could increase, along with tax revenues.
During intermittent floods, a new urban building network could deliver goods and services via the resilient, supplementary, smaller scaled elevated street network. Emergency transports might also use such a system, though rooftop helipads might be interspersed. The elevated network would become more robust and resilient as the blocks are developed in phases.
As the new urban building network develops in the 100-Acres district, starting with elevation of A Street where it intersects with Summer Street as a new high street development spine, the existing street network below would gradually convert to an atgrade public realm for recreation, parking, and other activities that can withstand intermittent flooding and rising tidal flows. Deteriorating infrastructure at the edges of the area could be removed and the land regraded and planted to become a more absorbent water management system and urban parkland. As a mixture of residential, commercial, recreational, lodging, medical, and other uses and services develops, parking demand could decline. Shared and autonomous vehicles may also facilitate remote or alternative parking scenarios.
To give the public access to privately owned land at grade and coordinated access above, private developers could provide public easements for connections and build circulation through blocks and buildings as part of each development project in exchange for being able to develop at higher density above ground level. If the market can support additional development, such density bonuses and conversion of industrial areas to urban uses could increase the city’s tax base to a level where revenues pay off bonds used to build infrastructure offered by the city as an incentive for development. The private sector could lease its ground plane to the public sector for gradual conversion to open space and other floodable uses in exchange for construction of public infrastructure and provision of maintenance, while the private sector retains parking rights for floodable areas under the buildings.
In the case of the 100-Acres, Utile notes that 40 percent of the land already consists of private parking lots held by just four major landowners—Procter & Gamble/Gillette, the U.S. Post Office, Beacon Capital Partners, and the Archon Group, a global real estate investment services and asset management firm. If BRA or another public entity can aggregate the parking lots and streets in exchange for brownfield remediation, construction of public infrastructure, and maintenance of floodable areas—while permitting private owners to retain development air rights at higher density—then the public sector might own the majority of the ground plane, giving the public the ability to control circulation, floodplain management, and public access.
Conversely, the BRA might only help facilitate land acquisition by private developers with enough resources, commitment, and control to invest the larger sums necessary to create a connected, integrated, elevated inverse urban network. Either public or private investors would need to invest for long-term returns.
One could assume that the optimal time for private or public investors to acquire undeveloped land would be now, when land values are assumed to be at their lowest, rather than later when values could escalate from conversion of properties from industrial to more urban uses made more resilient under the Utile plan. However, rising sea levels and increased storm surges could also raise the costs of elevated infrastructure and increase liabilities beyond economic feasibility.
One could argue that for the 100Acres district, those value increases will not come unless sound public/ private partnerships exist to create the elevated inverse blocks, because otherwise the land would simply be inundated. And rational private developers would build there only with firm assurance that the elevated network will be built. Yet the city has little money to build elevated infrastructure without private investment. So both public and private developers need each other, and concrete, enforceable public/ private partnerships can be a better way to direct development than traditional regulatory techniques.
Precedents exist for elements of this type of development. The 1733 plan for Savannah, Georgia, created a public space at the center of each ward from which one can look in all four directions through to another public space. There are mixed precedents regarding elevated pedestrian levels. The High Line in New York City demonstrates that an elevated pedestrian way can draw new activity and development. The Minneapolis Skyway system demonstrates that enclosed sky bridges can draw pedestrian traffic from the streets, but not enough retail interest to sustain the system or enough public space to activate it or vehicular circulation to service it.
In the case of the 100-Acres district in Boston, rising sea levels and storm surges create the need to combine vehicular and pedestrian circulation, as well as decentralized infrastructure, elevated above the street—and a potential opportunity to integrate the public realm. The focused, resilient central urbanity of the inverse block structure could be developed more cost-effectively than elevating a neotraditional peripheral street grid, but it also might create an alternative to simply moving to higher ground, the more economical alternative.
WILLIAM P. MACHT is a professor of urban planning and development at the Center for Real Estate at Portland State University in Oregon and a development consultant.
(Comments about projects profiled in this column, as well as proposals for future profiles, should be directed to the author at firstname.lastname@example.org.)