SAN FRANCISCO (CBS SF) – For months the barriers near Union Square have been the only visible sign to San Franciscans that work on the Central Subway was underway.

The city’s first subway effort in two generations is now 65 percent finished and the underground stations that will move passengers along the expanded “T” line are slowly taking shape.

The Central Subway will run north from the Caltrain station, heading underground as it passes under Moscone Center and Market Street before ending at another subway stop in Chinatown.

The project’s largest station will be under the tourist mecca of Union Square, and KPIX 5 got an exclusive look inside.

“Across the street from Macy’s, right down into the station,” explains John Funghi, project manager for the Central Subway. “We purchased some substandard underground parking and have converted it into the northern entrance of the station.”

Funghi is walking through what will become the Union Square Muni station, partially carved out of the old Union Square parking garage.

From that entrance, it’s a deep plunge below the city, into a massive excavation that reveals the true size of this project — a three-level stack of pedestrian walkways, platforms and escalators.

Work is going on 12 hours a day, six days a week.

“We’re employing techniques that may be prevalent in Europe,” Funghi said. “Techniques that haven’t been fully utilized here in the us.”

The largest single space is just beneath Stockton Street, and the crews that are working at the bottom of the room are actually digging their way to the tunnels that were carved out between South-of-Market and North Beach.

The upper level of that space is the corridor that will take passengers from Union Square over to Market Street.

At the corner of Stockton and Powell is the Southern end of the station.

“This is the old Apple store entrance that we purchased from BART for a dollar,” says Funghi.

At this end of the site, work is going on just a few feet away from commuters passing through the Powell Street Muni/BART station.

As for the digging that’s creating the new stations, there is a massive amount of dirt and mud generated. Most of it is delivered to Treasure Island, and with 30 more feet to dig before crews finally hit the tunnels, there is more mud to come.

The Central Subway is the city’s first transportation tunneling project since the 1960s. In that respect – there are two bits of good news from below ground.

First, that infamous San Francisco soil wasn’t as bad as expected.

“We’ve encountered some pretty good ground,” Funghi said. “Competent ground that’s very conducive to tunneling.”

That could make future projects more feasible – which leads to the subject of money.

With a budget of about $1.6 billion, the 1.7-mile Central Subway costs about $176,000 per foot. By way of perspective, New York City just opened the Second Avenue Subway, just two miles of work that ended up costing nearly $4.5 billion.

The job is also relatively on schedule. Workers on 4th street are laying groundwork for the surface tracks, and just up the street, they’re pouring the foundation inside what will be the Yerba Buena subway station.

“It looks like we’ll be finished from the south a little bit earlier, then be completing from the south and moving north,” Funghi said. “ We’re slated to be done in 2019.”