Transit center takes shape, showing how a city transforms

Iron workers bolt together connections between structural steel beams over First Street as work continued on the Transbay Terminal on Monday night. Construction workers continued making progress on the structural steel portion of the Transbay Terminal in San Francisco , Calif., on Monday, May 11, 2015. The project reached a milestone as the decks that crossed over First Street were placed over the blocked roadway over the previous weekend and work continued overnight to finish the project. less Iron workers bolt together connections between structural steel beams over First Street as work continued on the Transbay Terminal on Monday night. Construction workers continued making progress on the ... more Photo: Carlos Avila Gonzalez, The Chronicle Photo: Carlos Avila Gonzalez, The Chronicle Image 1 of / 19 Caption Close Transit center takes shape, showing how a city transforms 1 / 19 Back to Gallery

Even by the standards of today’s downtown San Francisco, where new towers seem to pop up on all sides, what’s happening on First Street is one for the books.

Each night, masses of steel are being bolted into place across four lanes of the roadway that connects the Financial District to the Bay Bridge, forming a gaunt span that begins 25 feet above the sidewalk. This is the most visible section yet of the skeleton for the new Transbay Transit Center, the long-promised “Grand Central Station of the West” set to open in 2017.

The methodical leap occurred with neither fanfare nor fuss, but it deserves notice nonetheless — if only to remind us that the reshaping of a city is more profound and lasting than the controversies stirred by the initiatives that put large changes in motion.

Keep this in mind as Mayor Ed Lee’s administration suggests tearing down the north end of Interstate 280 and rerouting the train tracks scheduled to make their way to the transit center in 10 years or so. Or as a privately financed arena proposal for the Golden State Warriors is attacked by a handful of well-connected critics who would rather see the land go to UCSF Mission Bay.

Such dramas are inevitable in a city like San Francisco, where symbolic brushfires often draw more attention than deeper shifts. Grand plans are floated, to sink or swim. The ones that stay in motion must navigate the rapids of politics and second-guessing. After all that comes the last part, the physical transformation, the chapter in the saga that attracts relatively little attention — until “suddenly” the landscape is disrupted right before our eyes.

In the case of the transit center that will parallel Mission Street for a quarter mile, spanning First and Fremont streets along the way, it’s replacing the original Timothy Pflueger-designed terminal that was demolished in 2011. But not until last winter did anything appear above the ground. Even then, the first few sections rose to the west of First Street, hidden behind office towers unless you knew where to look.

This month, the show became impossible to miss.

First Street is closed each night between 8 p.m. and 6 a.m. while steel is installed for the future station’s “bones,” the girders and beams and decking that extend across the roadway’s 104-foot width. Around them are the spider-like “basket columns” that form the outer frame and will give the elongated structure its march of steady rippled curves.

Work occurs during the day as well, both above the ground and inside the enormous subterranean concourse areas intended to welcome commuter trains from the Peninsula and high-speed rail from Southern California.

But the head-turning advances take place under cover of darkness, an eastward extension that will cross Fremont Street and then conclude at Beale Street next March.

Someday, I’ll wager, the Warriors arena will rise in a similar way across from UCSF Mission Bay, next to a waterfront park at 16th Street. Maybe we’ll even live to see I-280 rolled back (though given the city’s ever-thicker traffic molasses, I’m not betting on that scenario). The saber-rattling showdowns will be footnotes in the past.

That’s what happened with the new transit center.

Our new terminal has been in the cards since 1999, when voters decreed that any new terminal must be in the same location as the one that opened in 1939 with a direct connection to the Bay Bridge.

Another five years passed while decision-makers came to embrace the idea of turning it into a rail hub as well, conceiving a larger neighborhood plan that includes a handful of extra-tall towers to help fund the project by way of land sales and developer fees.

At the 11th hour, critics sought to move the terminal several blocks to the east. The skin of the future terminal was changed from clear glass to perforated metal to cut costs. The much-hyped rooftop park was threatened briefly, and tower developers blustered in an unsuccessful bid to make the city agree to lower the fees they’re required to pay.

Nor have the dramas ended. There’s the very real question of how the terminal’s second phase will be financed, the one intended to extend rail service north from Fourth and King streets and make Transbay into something more than an oversized bus station.

The Lee administration’s theoretical redo of I-280 and the rail approach would open a new can of unknowns.

In the meantime, that basket frame and its steel innards will continue to expand. The basket will be coated in those perforated metal panels.

In the months to come we’ll also see a new bridge across Howard Street so that buses will once again have a direct connection to the Bay Bridge — and our imperfect but intriguing future will draw closer by the day.

Place appears on Wednesdays. John King is The San Francisco Chronicle’s urban design writer. E-mail: jking@sfchronicle.com Twitter: @johnkingsfchron