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A comment on Why New York City Stopped Building Subways. Parent comment

Re:Why New York City Stopped Building Subways by woodruffw on Monday April 16, 2018 @04:24PM (#16852379)
In addition to what others have said about the disruptiveness of cut-and-cover, it's worth noting that Manhattan's bedrock is almost entirely schist[1].

I don't know whether that was ever factored into the decision to bore instead of cut, but I'd bet that cutting through schist is a lot harder than the chalk and clay of London and Paris.

[1]: https://blog.epa.gov/blog/tag/manhattan-schist/

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Re:Why New York City Stopped Building Subways by nerdponx on Monday April 16, 2018 @04:27PM (#16852412)
The original subway tunnels were built with cut and cover, so that isn't an issue.
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Re:Why New York City Stopped Building Subways by woodruffw on Monday April 16, 2018 @07:12PM (#16853808)
I did some research, and it looks like the IRT was constructed with a mixture of cut-and-cover and boring[1]. The schist apparently isn't too much of an issue when you have dynamite[2] ;)

[1]: https://mhdh.library.columbia.edu/exhibits/show/irt/laying-t...

[2]: https://www.nypl.org/blog/2015/05/04/subway-construction-the...

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