Integrated firm AECOM and global firm Arup celebrated the completion of the first phase of the Second Avenue Subway for the Metropolitan Transportation Authority (MTA) earlier this year.
It is the first major expansion of New York City subway system done by the AECOM-Arup Joint Venture (JV) in nearly a century. The 1.8 mile stretch of track runs between 63rd and 96th streets and consists of three new stations, and one upgraded station. The JV provided full engineering and architectural services for Phase 1 of the $4.451-million 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,” says New York MTA transit/rail manager senior VP Julie D’Orazio.
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,” says Arup principal Craig Covil.
Serving about 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.
Multiple Roles and 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 JV responded to this situation with services that extend beyond conventional engineering.
Among these were tunnelling, with AECOM-Arup taking a total design approach to the tunnel construction, encompassing 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, 22ʹ1ʺ diameter tunnels for 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.
Geotechnical services were also provided as AECOM-Arup’s geotechnical experts applied their cross-disciplinary skills in foundation and landfill engineering, hydrology, engineering geology and other specialised services to reduce design and construction risks.
Another service provided was acoustics. Working with recordings taken at existing subway stations, as part of the JV 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 typical of 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 fibreglass and new, carefully orientated public-address speakers as part of a complete audio system that is optimised for intelligibility.
Moreover, tunnel ventilation services were provided. 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 comply 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.
Further, pedestrian modelling services were provided. 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.
Lastly, station services were provided. The JV 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, 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.