Ever wonder how BART tunneled under the streets of San Francisco? Check out this film from our archives. Watch the full version on our YouTube page or at the link in bio. Two Calweld oscillating tunnel-boring machines were used to bore twin mile-long tunnels between the Mission Street lines and the Market Street lines. BART quickly picked up on the nickname of the machine, “the Mole”—which was how these machines were affectionately referred to in tunnel digs around the world—when it commissioned