Under San Francisco’s streets is Mom Chung, the massive subway tunnel-digging machine that will help provide the city with a Central Subway, the new subterranean transit line that’s estimated to be completed come 2019. Mom Chung started digging this past July and for the last five months has been hard at work barreling through up to 40 feet of bedrock, clay and sand a day in hopes of finishing it on time.
Weighing in at 750 tons, Mom Chung is working alongside another monstrous machine, Big Alma, to excavate the long tunnels from Caltrain Station in SoMA all the way through Union Square to end up in Chinatown. Those above on land won’t feel a thing as these two beats are hard at work since they’re running from 4o to 120 deep, but those working in the tunnels must be feeling quake-like vibrations! The Central Subway blog is providing a detailed look at the process, which is pretty fascinating. There’s also a number of fun TBM Twitter accounts that share pics of their findings and provide a goofy personality to both Big Alma and Mom Chung.