Three weeks after steel bolts snapped on the new Bay Bridge, Caltrans is still working to find the cause, choose a permanent fix and identify all the steel parts on the rest of the span that came from the same manufacturer.
A possible manufacturing glitch or nuts that were perhaps wrenched too tightly are among the reasons under investigation. And the long-term engineering solution mentioned most often is an exterior steel sheath that would clamp together the affected bridge pieces.
But there are no definitive answers yet, and the $1 million dollar price tag being bandied about in the media in the past few days is a "highly preliminary estimate," said a Caltrans spokesman. The bridge construction budget includes a $300 million contingency fund.
Caltrans Director Malcolm Dougherty has put into writing the agency's investigation plan, which includes a reinspection of all other parts for the bridge supplied by Ohio-based Dyson.
"I want to reiterate that safety of the bridge once opened is the paramount and controlling factor in all decision-making on this issue," Dougherty wrote in his March 29 memo issued shortly after the agency briefed Bay Area transportation leaders.
Among Dougherty's directives:
High-strength steel can become brittle if exposed to hydrogen during the manufacturing or galvanizing processes, according to metallurgical engineers. Hydrogen atoms work their way into the spaces between the other elements and weaken the bonds that make the product strong.
The dearth of details is frustrating as the $6.4 billion bridge nears the end of 11 years of construction, agreed Senate Transportation Committee Chairman Mark DeSaulnier, D-Concord.
Over and over, Caltrans has said that it does not expect the bolt problems to delay the Labor Day opening of the new bridge, even though it can't say how it will overcome the construction setback.
"It's been 24 years since Loma Prieta, and we know the current bridge we're using is unsafe," DeSaulnier said. "But I'm relying on (California Business, Transportation and Housing) Secretary Brian Kelly to make sure that Caltrans gets the work done and can give us a report within two weeks."
The furor centers on the third of the 96 threaded steel rods -- 3 inches thick and 9 to 24 feet long -- that snapped in early March after crews tightened them down with nuts.
The rods are part of two massive steel and concrete seismic components called shear keys -- 11.2 feet tall by 11.2 feet wide by 5.75 feet deep apiece -- sandwiched between the bridge deck and the top of the pier just east of the main tower.
Bolted to the bridge deck above and the pier below, the devices help counteract movement during an earthquake and keep the two parts aligned.
With only 5 feet of clearance, crews don't have enough room to replace the broken rods, and engineers are looking for another way to clamp the pieces together.
The remaining 192 rods within adjacent shear keys and bearings can be replaced, Caltrans has said.
The devices are part of the new span's numerous seismic safety features and don't affect its day-to-day structural integrity. In other words, they are only critical during a big temblor.
Even with the broken rods, the new bridge is much safer than the existing cantilever, which rests on wooden timbers floating in the bay mud.
We asked Caltrans why steel rods snapped on the new Bay Bridge, how they intended to fix the problem and how much the repair will cost, but they don't have many answers:
Question: What exactly is the fix being proposed?
Answer: Several potential fixes are being considered, but one has not been selected yet.
Question: Where will Caltrans obtain the replacement rods?
Answer: It has not been determined whether those rods will need to be replaced, and if they do need to be replaced, where they will be obtained.
Question: How will Caltrans test the new rods to make sure they won't break?
Answer: Fabrication and testing data is still being compiled. Once all of that data has been gathered, Caltrans will know which tests need to be conducted to ensure that any new rods meet our specifications.
Question: What is the cost of the repairs?
Answer: The cost of the fix has not been determined, as a fix for the broken rods has not been selected and it has not been determined whether other rods will need to be replaced.