From tunnel to track, the Aecom-Arup joint venture engineered New York City’s newest subway line
The Aecom-Arup joint venture celebrated the completion of the first phase of the Second Avenue Subway for the Metropolitan Transportation Authority (MTA). The first major expansion of New York City’s subway system in nearly a century, the 1.8 mile stretch of track runs between 63rd and 96th streets and consists of three new stations, plus one upgraded station. The Aecom-Arup joint venture provided full engineering and architectural services for the first phase of the $4.451bn landmark project, which broke ground in April 2007.
"The on-time completion of the first phase of the Second Avenue Subway is a major achievement. The engineering and design ingenuity represents our best-in-class approach to large-scale transit projects. We thank the MTA and the governor’s office for their guidance and support; because of it the project met the completion deadline set in 2009. We are excited for New York City residents to experience this iconic new subway line," Julie D’Orazio, Aecom senior vice president, NY Metro transit/rail manager said.
The Second Avenue Subway is part of Governor Andrew Cuomo’s proposed programme for improving transportation infrastructure throughout the state, to ensure those who live, work, and travel in New York have a safe, efficient, balanced, and environmentally sound transportation system.
"The opening of the Second Avenue Subway will immediately improve the quality of life for thousands of New Yorkers. Designing and delivering such a complex project required the complete collaboration and unwavering effort of a robust team of engineers and contractors, and would not have been possible without the strong leadership and vision of the MTA and the governor’s office,” Craig Covil, Arup principal explained.
Serving approximately 200,000 daily riders, the first phase of the Second Avenue Subway will improve travel for both city and suburban commuters on Manhattan’s east side. On an average weekday, it will relieve overcrowded conditions on the nearby Lexington line by as much as 13% (23,500 riders). The project, initially imagined in 1929 and derailed by the Great Depression, will eventually run 8.5 miles along the east side of Manhattan.
"The Second Avenue Subway is a transformative project that takes a leap forward in engineering and design innovation of a transit system. We are very proud to have been a part of the project. Its success is a testament to the hard work, dedication, and close collaboration with the contractors," Liam Dalton, project manager at Aecom commented.
Multiple roles, critical responsibilities
An intricate balance of infrastructure, buildings, and transit, the Second Avenue Subway project called for a comprehensive approach, one that recognised the social, economic, and environmental issues facing the city of New York. Capitalising on its multidisciplinary capabilities and global expertise, the Aecom-Arup joint venture responded to this situation with services that extend beyond conventional engineering.
Aecom-Arup took a total design approach to the tunnel construction, one that encompassed life safety issues, ventilation systems, material science, and other factors to create a cost-effective and sustainable design. A tunnel-boring machine was employed to excavate the 12,800 feet of twin-track, 22'-1" diameter tunnels in the first phase of the Second Avenue Subway. The one expanded and three new stations on the line are some of the largest underground excavations in North America, ranging from 57 to 64 feet in width and up to 1,591 feet in length. Adding to the complexity of the job, these mined caverns all have escalator and elevator connections to street level — features much appreciated by riders who have long endured stairway-only access.
The Second Avenue Subway is sited below and amid some of the most congested urban infrastructure in the world. Navigating the maze of telecommunications, electrical, gas, steam, water, and sewage lines that lie below the asphalt required intensive study and farsighted solutions. Aecom-Arup’s geotechnical experts applied their interconnected skills in foundation and landfill engineering, hydrology, engineering geology, and other specialised services to reduce design and construction risks.
Working with recordings taken at existing subway stations, as part of the joint venture efforts Arup’s acousticians used the firm’s SoundLab technology to create digital models of the environment and determine the best way to quiet the bone-rattling noise typically found in the subway. The solutions include joint-free train tracks with ties that are encased in concrete-covered rubber, ceilings lined with perforated metal panels that are backed with sound-absorbing fiberglass (instead of the echo-prone tile and stone used in other parts of the transit system), and new, carefully oriented public-address speakers as part of a complete audio system that is optimised for intelligibility.
The design for the Second Avenue Subway included three new stations 96th, 86th, 72nd street, and the reuse of existing subway stations and tunnels at 63rd street, which required significant updates to be in compliance with modern codes and standards. This, combined with the limited space for the mechanical and electrical systems, necessitated careful planning and creative engineering solutions to bring the existing systems up to code while remaining cost effective. In some instances, mechanical ventilation was employed while other areas necessitated air conditioning treatments.
In the absence of a robust set of design guidelines for a new, modern subway line, the Aecom-Arup team worked with New York City Transit (NYCT) Operations Planning to set out design parameters and performance metrics. Using a newly developed model to simulate 3,000 uptown and downtown train arrival combinations, the team generated dynamic pedestrian model simulations for all stations for the morning rush hour. These simulations were used as a design tool to inform the optimal circulation paths for moving passengers between trains and the street level, even taking into account the complex movement associated with transfer passengers at 63rd street, and the challenges at 86th and 72nd streets, where abnormally deep stations necessitate increased use of elevator access.
Aecom-Arup led the multidisciplinary design of the four new underground stations. Working from a new set of NYCT station guidelines developed specifically for the Second Avenue Subway project, the design includes architectural detailing, ADA Compliance, high ceilings, column-free design, dramatic lighting, top-level acoustics, added safety and security, and world-class artwork. All this combines to make these new stations a historic addition to the NYC subway system and the Upper East Side community.