Tutor Perini construction crews work underneath Union Square on Wednesday night during a media tour as the Central Subway tunnel project reached a significant milestone. (Joe Fitzgerald Rodriguez/S.F. Examiner)

Tutor Perini construction crews work underneath Union Square on Wednesday night during a media tour as the Central Subway tunnel project reached a significant milestone. (Joe Fitzgerald Rodriguez/S.F. Examiner)

Crews reach milestone in construction of Central Subway

“Clank!” the machine rang, followed by silence. “Clank!” and silence once again. “Clank!”

The sound of a concrete-pouring machine echoed from underground, out onto Stockton and Market streets on the surface, signaling the effort below.

More than 100 feet under Macy’s in Union Square, dozens of yellow- and orange-clad workers from Tutor Perini construction company reached a key milestone in building the Central Subway.

On Wednesday night, the last ounce of concrete creating the Central Subway’s Union Square station floor was poured, leaving only a few major milestones left before the tunnels and stations are completed in 2019, according to the San Francisco Municipal Transportation Agency.

That floor was finished that night. In two years, more than 38,000 daily travelers will rely on the trains that coast through the $1.6 billion subway.

The project as a whole is delayed by 10 months, as the San Francisco Examiner previously reported. The delays impact Chinatown neighbors near that subway station, but the Union Square subway station construction is on schedule, according to the SFMTA.

“You need the right mindset to do this,” said John Funghi, the Central Subway’s program director. The workers must endure small spaces, dark tunnels, the (distant, but real) threat of gas leaks and more hazards found when digging stories deep into the bowels of The City.

On Wednesday, Funghi allowed several media outlets — including the Examiner — to get a taste of that work, during a rare tour of the Central Subway construction.

Reporters walked through a future entrance to the Union Square station, which rests in its parking garage, under the plaza. What now is slats of plywood jury-rigged into a door will soon be a full fledged subway station entrance.

Immediately inside, a railing constructed of simple 2-foot-by-4-foot wood, slotted into metal posts, was all between reporters and a 40-foot drop below, the least of the impressive heights. Peering over, piles of earth littered with blue plastic child-sized swimming pools (to mix concrete in), and construction machines, would soon house future escalators down to the station.

Other features were half finished: Sparks flew as workers welded steel at an emergency exit that leads to Macy’s men’s store, and a brick wall at the end of the station would soon be knocked down to create an underground walkway to BART.

The only way to see the breadth of the work, however, was to walk into the station on the extreme sides, on a narrow 2-foot-wide steel catwalk.

Some on the tour experienced a sense of vertigo, as the slight drop opened up into an 80-foot chasm to the concrete pouring below. Wide steel pylons, half the width of a car, bridged the walls.

Funghi noted that construction underneath San Francisco’s businesses, from Chinatown to Union Square, takes skill to undertake and not disturb the surrounding earth. In some portions, the excavation of the station skirted just 7 feet away from a BART tunnel — a delicate digging procedure, akin to surgery with a jackhammer.

The station platform stood below, 335 feet long, held by more than 107 cubic yards of poured concrete. Workers stay until 11 p.m. some nights, though at the Chinatown Station workers are active 24 hours a day to catch up with the recently revealed delay, Funghi said.

Down below, the two tunnel openings to the future Chinatown station could be seen, just a stone’s throw from where the last ounces of concrete splashed.

The grey matter gurgled and then rushed out of an oversized hose, the circumference of a jug of water. The hose moved with so much power, it had to be tied by rope to beams above, as some workers knelt on it, while it wriggled, writhed and bucked beneath them.

It was like a construction rodeo. Instead of bragging rights, however, a station was being built.

The concrete filled the floor between hundreds of slender steel struts, which criss-crossed in a grid at the station’s lowest point, about 105 feet below street-level. Other workers then shoveled the concrete, and tamped it down with a tool resembling an overly-wide mop.

“We’ve bottomed out the station,” Funghi said, beaming proudly. Transit

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