Mom Chung and Big Alma to bore SFMTA Central Subway tunnels

Written by Jenifer Nunez, assistant editor
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Mom Chung one of two tunnel boring machines that will construct and excavate SFMTA’s Central Subway tunnels.
Barnard Impregilo Healy

The San Francisco Municipal Transportation Agency (SFMTA) revealed the names of two tunnel boring machines (TBMs) that will excavate and construct the Central Subway tunnels.

The two tunneling machines will be named Big Alma, after “Big Alma” de Bretteville Spreckels, and Mom Chung, after Dr. Margaret “Mom” Chung.

The first of the machines, Mom Chung, is expected to arrive in San Francisco in April. The 300-foot-long machine will be assembled within an excavation on 4th Street between Harrison and Bryant streets and will start building the tunnel for southbound trains about two months later. Big Alma will arrive soon after Mom Chung to construct the northbound tunnel.

“These two state-of-the-art machines will help us connect our most dense and fastest growing neighborhoods in San Francisco. From South of Market to Chinatown, the Central Subway will bridge our vibrant communities and vastly improve transportation options for residents and visitors,” said San Francisco Mayor Edwin Lee.

The names were selected by the public in an online poll held in January. Participants could select up to two names, one for each TBM. Of the 1,453 responses, Big Alma was the top vote-getter at 682 votes. Mom Chung took second place with 487 votes, closely followed by Firebelle Lil (451 votes), Mary Ellen (437 votes) and Juana (148 votes).

In tunneling tradition, the custom of naming TBMs is believed to bring good luck to tunneling projects. The names will remain in official use by the SFMTA and the tunneling contractor throughout the duration of the project.

The Central Subway Project will extend the T Third Line from the 4th Street Caltrain Station to Chinatown, providing a direct, rapid transit link from the Bayshore and Mission Bay areas to SoMa and downtown. Four new stations will be built along the 1.7-mile Central Subway Project alignment, a street-level station and three subway stations.

The Central Subway Project is the second phase of the SFMTA’s Third Street Light Rail Transit Project. The $1.6-billion project will be funded using a variety of federal, state and local sources, including $942.2 million from the federal New Starts program. Of the total New Starts investment, $177.4 million has already been awarded to the Central Subway Project and a Full Funding Grant Agreement was awarded in October 2012.

Categories: ON Track Maintenance, Rapid Transit/Light Rail, Track Machinery