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Central Subway: A "Boring" Success

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Monday, March 2, 2015

If you think packing up your moving boxes is a laborious affair, check out this time-lapse video of the disassembly of the Central Subway’s twin tunnel boring machines (TBMs), affectionately known as Mom Chung and Big Alma.

Last June the Central Subway project marked a major milestone as the TBMs broke through into the subway’s retrieval shaft located in North Beach, completing the excavation of both tunnels. With the excavation finished, focus turned toward extricating the massive TBMs from the retrieval shaft. A slow and methodical process was used to de-pressurize and take apart the machines into multiple pieces. Removal of the TBMs was completed late last year with final site cleanup being completed in early January.

While TBM removal stole most of the attention, other Central Subway work crews were busy on multiple fronts including on the site of the future Union Square-Market Street Station, where workers successfully installed all 468 foundation support beams, and at the subway’s portal, underneath the I-80 freeway, where work is now 50 percent complete.

While work on the Central Subway continues, Mama Chung and Big Alma (eager to tear up more dirt) take a rest as they await resale to another tunneling project.

Learn more about the Central Subway or follow its progress by visiting our sister blog,

You may also enjoy the project's year in review from December: