NBC Bay Area got a first-hand look Saturday inside San Francisco's Central Subway Project that will transport people between the Caltrain station and Chinatown with several stops in between--and possibly to North Beach.
NBC Bay Area went 70 feet below ground where the Muni tunnel is being dug.
Two huge, 750-ton tunnel-boring machines are doing the work around the clock, digging about 50 feet per day. And at times, they have to dip 100 feet below ground to get underneath the BART tunnel along Market Street.
And things got a little tight.
"To make a perpendicular cross with the BART tunnels and separation was about 7 to 10 feet," Central Subway Program Director John Funghi said. "So the clearance from the top of our tunnel to the bottom of the BART tunnel was a 7 to 10 foot separation."
"This was one of the biggest engineering challenges of the project going under existing tracks," Funghi added. "From a complexity issue, the engineering challenge--building a tunnel underneath an existing operating line."
But San Francisco Mayor Ed Lee said it is one of the most important projects for the future of San Francisco. It's expected to open in 2019.
"Construction phase goes to May," Muni Spokesman Paul Rose said. "Then, we'll take out the bore machines, continue work on the stations. 2018 the work will be done. 2019 the service will start."