EVAN DUCHARME/SPECIAL TO THE  S.F. EXAMINERWork continues Wednesday at the Transbay Transit Center site downtown.

EVAN DUCHARME/SPECIAL TO THE S.F. EXAMINERWork continues Wednesday at the Transbay Transit Center site downtown.

Transbay site work reaches milestone

Sixty-five feet below ground level between Mission, Howard, Second and Beale streets, crews working on the Transbay Transit Center project reached a quiet milestone.

A 10- to 12-hour concrete pour completed Saturday was the last one necessary until excavation wraps up early next year. That makes 10 mat slab pours to date, each between 4,000 to 6,000 cubic yards of concrete. Rail tracks will eventually sit on the slabs.

“This is achieving a big milestone for our project,” said project superintendent Jordan Smith of Webcor/Obayashi, the general contractor, at the site Wednesday. “Essentially half of the project has mat slab. What that allows us to do is continue on schedule on the walls and columns and rebar on one side.”

Construction has made good time, with the foundation for the western half of the 600,000-cubic-yard hole in the ground already set with mat slab.

The multilayer process started in early September and involved drilling 65-foot-long micropiles on the dirt base to anchor the coming structure, four inches of concrete slab, a waterproofing layer, another 4 inches of concrete slab, rebar reinforcement and finally 5 feet of mat slab that Caltrain and high-speed rail will arrive on.

Dirt is still visible in the easternmost portion of San Francisco’s biggest hole in the ground, with excavation slated to end in mid-January. The final mat slab pours will occur in mid-February.

In the western section and portions that already have mat slab, work has begun to focus on solidifying the walls, which also require waterproofing, rebar and a concrete finish. With construction materials, timing is paramount.

“It’s kind of a dance down there in terms of how things have to move forward,” said Monique Hawn, superintendent for Turner Construction, another contractor.

Hitting this milestone also enables another contractor to insert structural steel starting in the middle of the site and moving outward in both directions. The recent cold snap has had no bearing on the construction process and less-than-normal rainfall has “immensely” helped the project stay on schedule, Hawn said.

There has been “an amazing safety record,” added Transbay Joint Powers Authority spokeswoman Stephanie Reichin.

The first phase of the $4 billion project involves creating a five-story transit center with one above-grade bus level, a ground floor, concourse and two below-grade rail levels and a rooftop park. The project broke ground in August 2010 and is scheduled to be completed by fall 2017. It is expected to accommodate more than 100,000 passengers each weekday.Bay Area NewsTransbay Transit CenterTransittransportation

If you find our journalism valuable and relevant, please consider joining our Examiner membership program.
Find out more at www.sfexaminer.com/join/

Just Posted

Passengers ride the 14-Mission Muni bus on Friday, March 12, 2021. (Jordi Molina/Special to S.F. Examiner)
Transit officials fear Free Muni pilot could hurt already-strained service levels

Supporters say fare cuts could increase ridership, help low-income residents

The vacant property at 730 Stanyan St. in the Haight currently houses a safe sleeping site for the homeless. <ins>(Kevin N. Hume/S.F. Examiner)</ins>
Affordable housing project on former McDonald’s site delayed as city adds units

The start of construction on an affordable housing project on the site… Continue reading

Visitors read a notice hanging on the Polk Street entrance to City Hall on Thursday, March 26, 2020, shortly after the building was closed. (Kevin N. Hume/S.F. Examiner)
City Hall reopening to the public on June 7 after long closure due to COVID-19

San Francisco will reopen City Hall to the public on June 7… Continue reading

Historic streetcars are undergoing testing on The Embarcadero to prepare for their return to service on May 15.<ins></ins>
What to expect for Muni Metro’s relaunch on May 15

Significant service restoration includes downtown subway tunnels and historic streetcars

San Francisco 49ers quarterback Jimmy Garoppolo (10) and running back Raheem Mostert (31) celebrate after Mostert scores his fourth rushing touchdown in the third quarter as the 49ers take on the Green Bay Packers in the NFC Championship game at Levi’s Stadium in Santa Clara, Calif. on Sunday, Jan. 19, 2020. (Kevin N. Hume/S.F. Examiner)
49ers on prime-time TV five times in 2021

Usually a team that finishes in last place and won only six… Continue reading

Most Read