Going underground for city renewal
For more than half a century, the construction of urban freeways has sometimes been a blight on the United States landscape. What was meant to help in certain instances has taken away connectivity and open space. Replacing them with tunnels can reunite communities, provide new greenspace, and open up room for other amenities, writes Mike Wongkaew.
One of the unintended consequences of America’s huge road building program in the 1950s and 1960s was a mass of freeways running through the middle of urban areas. The Federal-Aid Highway Act of 1956 modernized the country’s road network, but by prioritizing traffic over people it also divided communities, brought air and noise pollution, and removed amenities from neighborhoods that the roads passed through or over.
As that mid-20th century infrastructure reaches the end of its natural life, urban planners and politicians are embracing a more people-centric vision as they seek replacement options. Cities are increasingly planning for a greener and more resilient future: one in which trees replace concrete and economic regeneration benefits people, businesses and the environment.
Tunneling advances liberate space above ground
Huge advances in tunneling technology offer cities the opportunity to regenerate their environments and improve the lives of residents by taking transportation underground and greening former urban highways.
The advent of larger, more powerful and sophisticated Tunnel Boring Machines (TBMs) during the 21st century has made underground infrastructure more feasible and practical. The large diameters of TBMs combined with computerized control and monitoring systems has helped to make tunnelling safer and more cost efficient as well as reducing disruption and environmental impact above ground.
AECOM deployed the world’s largest ever TBM, with a diameter of 17.6m (57.7 ft), in the construction of 5 km (3.1 mile) undersea tunnel that formed part of the Tuen Mun-Chek Lap Kok Link project in Hong Kong. The tunnel, a critical element of a project that has enhanced transportation around Hong Kong’s port and international airport, was a major engineering and construction feat that drew in AECOM expertise from Asia, the US and Europe.
Thanks to the latest generation of TBMs, tunnelling is gaining acceptance in the US as an important option for urban transport design.
Regenerating communities
The city of Seattle replaced the Alaskan Way Viaduct, an elevated stretch of State Route that carried 110,000 vehicles daily through the downtown and waterfront area, with a 3.2km bore tunnel that was built while the freeway remained open. The vacated land has been reclaimed for a revitalized waterfront that includes parks, walkways and commercial and cultural spaces.
A similar regeneration is underway in the state of New York where the Kensington Expressway, which divided communities in East Buffalo in the 1960s, is set to undergo a complete renovation. The state has revealed plans to send the six-lane highway underground and cover it with green space and improved facilities for residents.
Governor Kathy Hochul of New York, said that reconnecting neighborhoods “severed by asphalt highways,” was a cornerstone of the infrastructure vision to improve life in the state, and helped to promote equity in communities impacted by freeways.
“Better infrastructure means better quality of life, and the communities around the Kensington Expressway in Buffalo and across our state deserve nothing less,” she said. “These projects will help right the wrongs of the past through safer and reliable transit networks, landscapes designed to bring communities together, and routes that are friendlier for pedestrians and bikers.”
We are also seeing highways reimagined in other parts of New York, like in the Bronx where AECOM has helped reconnect the community to the waterfront, parklands and greenspaces that had been greatly restricted since the Bronx expressway was completed in 1963.
A full toolkit for urban renewal
Building tunneling in a city is a huge and complex operation. It requires a vast range of integrated services including planning and design, environmental assessments, extensive consultation with stakeholders and financing even before ground has been broken.
Once the TBM moves in, the heavy engineering can begin. This is when construction and project management is critical for bringing projects in on time and on budget. AECOM’s expertise encompasses all these disciplines, and we have extensive experience delivering successful tunneling projects in the US from New York’s Second Avenue Subway to the LA Metro Rail System.
A tunnel is only the beginning of the urban regeneration story. Making the best use of the land vacated by freeways is equally critical. Cities that want to optimize the return on their infrastructure investment can also benefit from the services we provide which include urban design, climate change adaption, integrated transport planning and resilience strategies.
We are passionate about building beautiful, sustainable urban environments that benefit people and the planet, and excited about bringing our expertise to America’s cities.