The CEE Department at Lehigh offered a field trip for all junior and senior CivE’s to the construction site of the new 2nd Avenue Subway being built in downtown Manhattan. The bus left campus at 5:30am, a Friday morning and we were in New York City by 7:15, right above the site. There were 16 of us students with a proctor and as we climbed down underneath the busy, traffic-filled street, we were handed hardhats, gloves, and safety vests and glasses. We entered an underground chamber with hundreds of other students and sat down for a short introductory presentation. The Moles are a special civil engineering society based around NYC that contains many of the designers and workers that helped construct a lot of big projects in the area over the years. Every year they offer a tour of a current, active site for civil engineering students of all colleges around. The site of the 2nd Avenue Subway is about as large as you can get.
Our tour consisted of 14 different stations, where a representative from a company explained their unique role in the project. We were not allowed to take any pictures so I’ll list the stations as best as I can from my memory:
1. Remediating concrete piles of any buildings whose foundations were damaged or settling unevenly due to the tunneling
2. Removing sludge wastewater out of the tunnels to set concrete walls around launch zone
3. Preparing the launch zone, or initial downward excavation where tunneling began, by digging around and redirecting utility lines
4. Using form work to mold concrete sections of the underground walls
5. Installing scaffolding underground to support concrete ceiling until fully dried
6. The actual process of tunneling directly below the street
7. The design of the station chamber that was 66′ tall!
8. The excavation of the station chamber from the street level 100′ above us
9. The geotechnical design of a single earth column at one end of the chamber
10. Laying the subway track down along with the electronics (lighting) in the tunnels
11. Earth freezing process – the tunnel cuts directly through solid bedrock except for one end where the weak soil layer dips down. Tunneling through that would have caused a sink hole in the street above. They decided to freeze that soil until the concrete tunnel was fully in place by running cooling pipes all throughout that ground area.
I forgot the other stations, but the ones here give an idea of how big the project really is. I could physically see the scale of it and it amazed me. All the firms that came together to work on this subway system cover every single aspect of civil engineering. Walking through those tunnels as it was being constructed was definitely one of the coolest experiences I’ve had at Lehigh.