WALKING through the new stations of the Second Avenue Subway, which opened on January 1 in New York City, is a rewarding experience for Mr Ken Griffin.
Griffin was the chief architect for the project, which finally delivered on a near century-old promise to extend the city’s Subway network to the upper east side of Manhattan. Around 155,000 weekday passengers are now using the four stations on the 4km extension, which runs from an expanded Lexington Avenue and 63rd Street station to 96th Street and Second Avenue via 72nd and 86th Streets.
“As an architect, I have worked on projects like this for over 40 years,” Griffin says. “Since they opened, I have often walked through the stations by myself, observing what is going on. People don’t know who I am and what I do but it is personally very rewarding and reassuring to hear how the stations have been received and the positive things being said; how comfortable people feel using the stations; how well-lit they are; and the fact that there is an escalator at every entrance.”
Project manager Mr Michael Trabold says he has had a similar experience. He recalls how people have approached him as he has walked through the site wearing high-visibility clothing to thank him for the work that has taken place.
“You realise you have created something that is having an impact on people’s lives,” Trabold says. “And a positive impact. Once it is open the people forget how long it took and how much it cost.”
Griffin is a vice president and Trabold an associate president at Aecom, which was appointed in April 2006 by Metropolitan Transportation Authority (MTA) in a joint venture partnership with Arup to provide full engineering and architectural services for the $US 4.451bn project. The JV design team had previously completed conceptual and preliminary engineering for the project. Ground was broken in April 2007, and while the project schedule and budget was revised in 2009, it was delivered on-time and on-budget according to these revisions.
Bringing together expertise from different companies, according to Trabold, was a major advantage for the project due to the varying experiences of the people involved. However, differences in philosophies and approaches when it actually came to do the work was a potential early stumbling block. Griffin says that in order to foster shared thinking and objectives, the emphasis from day one was not whether employees were from Aecom or Arup, but that they were from the Second Avenue Subway.
“We learned to leave our company in our old office,” Griffin says. “We didn’t have Aecom or Arup mugs, but Second Avenue Subway mugs, and Second Avenue Subway hard hats. The client sat among us as well and we were all part of the Second Avenue Subway team. In fact, if you brought in something or wore the branding of your employer, that was frowned upon.”
Pooling expertise in this way helped the project to deliver a number of innovative solutions not previously seen on New York City’s subway.
This includes altering acoustics in order to limit noise. Working with recordings taken at existing subway stations, Arup acousticians created digital models of the environment using the company’s SoundLab technology. This was subsequently analysed to identify ways to mitigate the effects. Solutions included utilising continuous-welded track with sleepers encased in concrete-covered rubber, ceilings lined with perforated metal panels backed with sound-absorbing fibreglass, and a carefully-positioned public address system, part of the line’s audio system that is optimised for intelligibility.
Optimal temperature control is another area where new solutions were deployed. Air tempering was used for the first time in stations, which is typically 10 degrees below the outside ambient and offers gradual temperature control to the exit.
Griffin says the project emphasised improving conditions for passengers by promoting a sense of calmness in the environment. This consideration is readily apparent in the open but simple station design. He says the design team wanted to make passengers feel less claustrophobic than in typical cut-and-cover New York subway stations, which are often criticised for feeling cramped and dingy, and were afforded this flexibility through the use of mining and TBM excavation.
With a width of 17-19.5m and a length of up to 485m, the Second Avenue Subway stations are some of the largest caverns excavated in North America, and according to New York governor, Mr Andrew Cuomo, have marked a new age for how stations are designed and built in New York.
The new stations are column-free at both the mezzanine and platform-level, and incorporate what Griffin describes as timeless but simple design features, evident in the white tiling, stainless steel and granite surfaces. Art displays are also a major element of each station, and collectively the Second Avenue Subway is now the largest public art display in New York state.
A new approach to lighting and illumination is another distinctive feature, with surfaces from the floor to the concrete ceiling lit in different ways. Griffin says this provides a more pleasant but safe passenger environment while promoting smooth passenger flow between the platforms and the stations’ two exits.
This is a key departure from the previous mandate for New York subway stations, which have four exits, and Griffin says are sometimes difficult to identify on the surface. He says that two larger entrances at either end, helped to reduce costs, and their location in plazas and at key interchanges has improved visibility at street level.
Griffin adds that while the station is an interesting passenger environment, specific elements were designed with the future in mind. “One of our major priorities was to introduce things that would enable the station to adapt to changes in technology,” Griffin says. “We have left space in the areas above and behind the architectural finishes. We also left room for additional capacity in the “service carriers,” which house the electrical and communication conduit and devices at the platform and mezzanine level. We designed spare conduits for future upgrades so new conduits would not be required, and left space in electrical panels for future expansion of communication systems.”
Passenger use of the stations is also not left to chance. The Second Avenue Subway team also worked alongside the Operations Planning team at New York City Transit on pedestrian modelling for each station.
Simulations of 3000 uptown and downtown train arrival combinations fed into the development of dynamic pedestrian model simulations for all stations during the morning rush hour. These simulations were subsequently used as a design tool to inform the optimal circulation paths for moving passengers between trains and street level. In particular, they took into account the complex movements associated with transfer passengers at 63rd Street, and the use of elevators at 86th and 72nd Streets.
“My personal observations of the 72nd Street station and the southeast entrance when the station gets busy is that it is a very comfortable experience for the passengers,” Griffin says. “We have planned with 2030-35 in mind, so we can accommodate a high circulation of passengers, and as ridership increases, we can introduce measures to facilitate this growth. It is a modular station design. For example, where we have concrete stairs at present, these are designed in such a way that it is straightforward to introduce an escalator directly in this space in the future.”
Designing an architecturally-pleasing environment that is adaptable to future need has not come at the cost of sustainability. Green materials were used throughout the project, including environmentally-friendly concrete, the primary building material. The granite panels were sourced from quarries in Pennsylvania and Virginia and were used in combination with terra cotta and porcelain ceramic wall panels. Glass was also used for entrance canopies and in entrances located inside buildings to maximise the use of natural light. Energy is saved through the use of escalators with a sleep mode and maintenance is minimised by not having any painted surfaces.
Preparing materials off-site ahead of installation was an approach used throughout the project in order to overcome the most significant challenge facing the Second Avenue Subway: minimising disruption to residents and businesses in the city that never sleeps.
Trabold says that while the project’s main work zones were on Second Avenue, the team was required to retain four lanes of operating traffic. In a 30m-wide right-of-way, with 2m reserved for the sidewalk compared with 6m previously, he says this left the subway project with around 9-12m to work in, which inevitably increased costs and implementation time.
Typically, subway entrances are located on sidewalks, which results in congestion and pedestrian choke points. He says that the team overcame this problem for the new line by using entrances located inside buildings and plaza areas where possible. But there will still issues. Following complaints at 72nd Street, work on entrance in the building had to move onto the street level.
Another difficulty was posed by restrictions on blasting, particularly at the 86th Street cavern. “We had up until 22.00 initially,” Trabold says. “However, the community objected to that so the cut-off point became 20.00. This made it much more difficult to do the work, and to arrange spoil removal through the night.”
Working in the confines of densely-populated neighbourhoods led MTA to engage in a significant amount of community outreach work. This began with meetings with local residents in the initial stages of the project and continued with the establishment of a community information centre where people could get information on what was happening, and were able to voice concerns.
Site visits were also arranged at weekends where hundreds of residents were able to see first-hand how the project was progressing. These tours were led by Dr Michael Horodniceanu, president of MTA Capital Construction, who Trabold says referred to residents as “constituents,” an important distinction as it reflected the importance to MTA of keeping its neighbours onside throughout the project process.
“The project was very disruptive to people’s lives. They were having to put up with this for seven to 10 years,” Trabold says. “MTA was very receptive to people’s concerns and treated them with sensitivity and respect.”
In addition, the project looked to promote social sustainability in the local community wherever possible; whether this was employing local electricians, carpenters and labourers, or engaging with local schools and colleges to use the site for educational purposes and to inspire the next-generation of engineers.
“Local college students regularly spent a day on the site where Aecom, Arup and the contractors could present the project to the students and other aspiring architectural engineers,” Griffin says. “One particular elementary school teacher would often walk the site with their students at street level so they could get a feel for what was going on. At an open-house for the 96th Street station just before the new line opened, some of the first people allowed to walk the station were those local school children and their teacher.”
When it came to the excavation work, the Second Avenue Subway team was faced with tunnelling beneath some of the most congested urban infrastructure in the world: telecommunications, sewers, electrical lines, gas, steam and water pipes litter the ground below Manhattan’s streets, and all could pose big problems for a major project.
Thankfully Trabold reports that when excavation got underway there were no huge surprises. Intensive studies meant that the utilities engineers expected to be there were there, apart from differences of a few feet in some cases. Yet there were a few notable unexpected items, including the wall of an old brewery at 96th Street, which was not mapped. Excavation teams also located foundations from the old Second Avenue tram line, and an existing sewer, the external structure of which was incorporated into the 96th Street station, a move which Griffin says saved a lot of money.
Great care and attention was also paid to preserving existing buildings during the excavation process. Trabold says in some cases the foundations for the structures, including timber piles, dated from the early 1900s. While in surprisingly good condition, they were showing signs of some deterioration and were reinforced. In one case an entire building had to be evacuated while it was rehabilitated to guarantee resident safety.
Ground conditions also posed some complications for the tunnelling work. A recent article in the New York Times showed a map of what is now New York City from the 1730-40s. The Hudson River is clearly visible, but Manhattan is dotted with areas of wet swampland as well as rivers and streams. Inevitably this makes tunnelling in the area a lot more problematic than it might appear on the streets of modern-day New York.
TBMs were used to excavate two parallel running tubes, and in a first for New York City, reinforcing steel fibres rather than steel rods were used between sections. Trabold says that the rock line is particularly high between 72nd and 86th streets. However, at around 92nd Street the rock line drops dramatically, and here the TBM excavating the eastern tube encountered a problem with weak fractured rock. Ground freezing was required to overcome the problem, which took a few months to carry out. However, with work able to progress on the western tube during this process, it did not delay tunnelling.
Teams also faced the challenge of integrating the new infrastructure with an existing cut-and-cover tunnel from the 1970s Second Avenue project which runs between 99th and 105th street. Trabold says they were not obliged to use this infrastructure but the decision was made to utilise what was a significant investment at the time. Adjustments were subsequently made to integrate with the alignment, and the tunnel is now in use to store trains for the 96th Street station, and is available to use as part of the next stage of the project.
Inevitably other cities have been keeping a close eye on what New York has been doing in the last 10 years, and it is very likely that the lessons of the Second Avenue Subway will be felt around the country. Griffin says that in particular transit schemes in Washington, Boston, Los Angeles, and Chicago could soon benefit from what was achieved.
The project is also serving as a confidence booster to New York. While challenging and certainly not cheap, Griffin and Trabold agree that the Second Avenue Subway shows that it is still possible to deliver large infrastructure projects in the city on time and on budget. And with this positive experience behind it, it is unlikely that New Yorkers will have to wait another 60 years for another extension to their subway network.
“The last two or three years have been very challenging,” Trabold says. “There has been a lot of pressure to complete a lot of work in a short period of time. Every day it seemed like there was a new problem to be solved. But when January 1 came around and we opened, we had time for a breather, and little bit of reflection. We could look back at what we had done and had achieved over the past 10 years with a great deal of pride.”