A few facts about San Francisco’s ongoing Central Subway project are beyond dispute:
It’s late. It’s over budget. It’s one of the most expensive public transit projects in terms of cost per mile in U.S. history. It stops well short of North Beach and Fisherman’s Wharf despite the fact that those neighborhoods will want train service in the future, and local businesses along the construction route hold it almost as an article of faith that the build is hurting revenue.
But it’s also really, really cool.
Hoping to keep San Franciscans enamored of the novelty and civic appeal of just how big of an undertaking the Central Subway is, the SFMTA uploaded a three-minute video to YouTube last week giving a boots-on-the-ground (or under it, as the case may be) look at construction of Chinatown Station.
The whole thing begins with a dizzying 12-story descent via crane into the depths of old San Francisco. The trip down reveals story after story laced with enormous support beams, a virtual underground city of scaffolding, and dozen of helmeted contractors laboring away like dwarves in their mines while the rest of the city goes about its business high above.
The video does not provide much in the way of explanation or guidance for what we’re seeing—the yellow plastic is weatherproofing material, for the record—but at least it drives home the ambition and concrete-encased grandeur of the work being done, which presumably was the idea.
SF Bay notes that almost all of the work involved with the excavation and construction on the line happening underground is the major driver in the ongoing delays, partly due to the fact that the city has employed the so-called New Austrian Tunneling Method (NATM) for the subway.
NATM dates to the 1960s and is particularly well suited for SF, as the German concrete pump company Putzmeister explains:
The method exhibits great resistance to the geological pressures seen in an earthquake-prone area. [...] Unlike the classical methods such as the Belgian or German approaches, where the tunnel is immediately supported without allowing it to deform naturally, NATM allows the deformation of the rock mass before stabilizing the tunnel, which reduces the amount of additional support materials required.
Obviously, that’s a coup for tunnel-making in San Francisco. But as tunnel engineer Fran Wilhelmstoetter told Tunnel Business Magazine (a trade publication for excavation companies) in 2016, “Using NATM it is still possible to create the [necessary] underground space, but it is more complicated with more steps involved,” citing Chinatown Station as an example.
Still, at least YouTubers can now get a close-up view of what’s really going on down there every day. The city hopes to have the Central Subway in operation by the end of 2019, although the worst case scenarios push the opening as far as 2021.
- SF’s Central Subway [Curbed SF]
- Central Subway Tour [YouTube]
- New Austrian Method [Putzer]
- Underground Station Design [Tunneling Online]
- It’s Late, It’s Expensive, It’s Chinatown Station [SF Bay]