MARE ISLAND -- In a cavernous shop where U.S. Navy submarines were once built, fabricators are deep into manufacturing the large custom steel saddles and cables for the Bay Bridge to restore the seismic safety features lost when 32 large anchor rods broke in March.
In a media tour Wednesday of the XKT Engineering machine shop where some of the work is underway, Caltrans engineers explained how the $10 million to $15 million retrofit strategy works and showed off the process for making the parts and pieces bound for the new eastern span.
None of the state engineers said anything new about when the span will open to traffic. Instead, the event was clearly meant to demonstrate progress on the permanent solution to the embarrassing screw-up that forced the three agencies overseeing the $6.4 billion bridge project to postpone the planned Sept. 3 opening for weeks or months until the retrofit is finished.
As for the temporary steel shims that outside bridge experts have said would allow the bridge to open to traffic in the interim, Caltrans Toll Bridge Program Manager Tony Anziano confirmed that outside peer review panelists and the Federal Highway Administration are expected to submit their seismic safety conclusion in mid-August.
No decision about an opening date will happen until after the analysis is finished, Anziano said.
In the meantime, XKT Engineering is forging ahead on a highly accelerated schedule.
The fix involves replacing the earthquake clamping forces lost when 32 out of 96 very large bolts -- 3 inches in diameter and 10 to 17 feet long -- snapped in March. The rods are embedded in two seismic stabilizers called shear keys sandwiched between the travel deck and the cap on the marine pier east of the main tower.
There's not enough room to replace the anchor rods in place, so engineers turned to an exterior fix.
A heavy steel saddle will be bolted to the top of each shear key, and cradle 142 steel ropelike tendons that snake down the outside of the pier cap.
Crews will tighten the cables and anchor them into the concrete pier cap. The entire saddle and cable assembly will be encased in a reinforced steel concrete blister.
"The retrofit will have the same tie-down forces as the original bolts," Caltrans senior engineer Bill Casey told the reporters.
Inside the fabricator's shop, the sheer size and scope of the endeavor is in full view. The saddles are actually comprised of seven layers of 3-inch-thick steel plates pushed through presses and shaped into tightly fitting, 24-foot lengths with curved ends. Grooves are then cut into the saddle pieces using milling machines outfitted with precision computer programs and titanium blades.
Each seven-layer saddle sandwich, as Caltrans engineer Jason Gramlick explained, will go into a giant press, where it will be mashed together. The seams will be welded on the outside.
After the 144,000-pound saddles are lifted by crane from a barge and placed onto the shear keys at the bridge, the contractor will thread the cables through the grooves and fill the tubes with grout. The entire saddle will be painted to protect against corrosion.
If federal engineers flash a green light on the use of the temporary shims and the bridge opens before the retrofit work is finished, the repairs will not impede traffic.
The contractor, American Bridge/Fluor Enterprises, will do the repairs from beneath the travel deck and bring up crews and materials from the water, Bay Bridge spokesman Andrew Gordon said.
XKT Engineering previously provided piles, expansion joints and service platforms for the skyway portion of the new eastern span and has worked on retrofits of the Golden Gate, Richmond-San Rafael, Benicia and Carquinez bridges.
In addition to XKT, Steward Machine Company of Birmingham, Ala., is also doing some of the fabrication work; Schwager Davis Inc. of San Jose is supplying the steel tendons; Harris-Salinas Rebar Inc. of Livermore is providing 260,000 pounds of reinforcing steel for the concrete; and Gonsalves & Santucci Inc. of Concord will be doing the concrete work.