Second Central Subway TBM launched

A second 750-tonne tunnel boring machine (TBM) has begun work on San Francisco’s Central Subway metro extension.

The city’s transit agency (SFMTA) has now launched ‘Big Alma’, who joins her sister Mom Chung in the construction of a $1.6 billion extension of the Muni Metro’s T Third Street line.

The TBM, which is named after 19th century socialite and philanthropist ‘Big Alma’ de Bretteville Spreckels, will now set about work on a 1.5-mile long tunnel beneath the city.

Announcing the launch of Big Alma, Mayor Edwin M. Lee said: “Today we are another big step closer to building the 21st century transportation system our world-class city needs and deserves.

“The Central Subway and the tunnels we are excavating today are essential to our vision, and crucial to building and maintaining a reliable, modern public transportation system for San Francisco residents and visitors.”




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