Central Subway tunnels reach key milestone

The South of Market portal entrance that will allow passengers to access 1.7 miles of tunnels that will make up San Francisco’s $1.56 billion Central Subway Project has been completed, project organizers announced Monday.

With the completion of this structure, located at Fourth and Harrison streets, the San Francisco Municipal Transportation Agency reports that the tunneling portion of the project remains on-time and on-budget.

SFMTA spokesman Paul Rose said Monday:

“Now we can continue to build the stations and construct the trackway.”

While passengers still won’t be able to board the new north-south serving subway system until 2019, the completion of the tunneling portion of the project marks a major milestone, according to the SFMTA.

San Francisco Mayor Ed Lee maintains that the Central Subway Project is worth the wait, as it:

“… will serve residents and visitors alike, especially in our growing neighborhoods of Mission Bay, SOMA, Visitacion Valley.”

The tunneling contract consisted of two massive tunnel boring machines that traversed the city between 40 and 120 feet below street level.

The two 350-foot-long tunnel boring machines that each weighed 750 tons, were affectionately named after historical figures, Dr. Margaret “Mom” Chung and “Big Alma” de Bretteville Spreckles.

The machines began their tunneling at Fourth and Harrison streets in the South of Market neighborhood in 2013 and resurfaced almost a year later in the North Beach neighborhood via Chinatown.

While there has been discussion about the extension of the Central Subway Project to the North Beach neighborhood, Rose said the Chinatown station currently remains the northernmost station planned.

The Chinatown station will be near the intersection of Columbus Avenue and Union Street, according to the SFMTA.

The portal at Fourth and Harrison streets will be where San Francisco Municipal railway’s existing T-Third line will connect with the new Central Subway.