Thursday, December 19, 2013
Transbay site work reaches milestone
by Jessica Kwong
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.
Read more at SFExaminer.com