Californians spent $6.4 billion to replace the old Bay Bridge eastern span because it was unlikely to survive a major earthquake. Now, mounting revelations of construction problems are calling into question whether the new bridge can withstand the Big One.

Tests showing signs of saltwater intrusion into the bridge tower’s foundation and damage to its anchor rods could be the most serious seismic issues for the project. But they aren’t the only ones. Substandard welds on the suspension span’s decks and water leaks near rods that secure the main cable also trouble engineers outside Caltrans who are experts in bridge construction and integrity.

The bridge is a designated “lifeline” — a road guaranteed to be accessible to emergency relief efforts soon after an earthquake. How its seismic issues are resolved will affect millions of people in San Francisco and the East Bay when a major quake hits and the outside world tries to rush in to help.

Despite all the recent bad news, Caltrans’ chief engineer for the bridge project, Brian Maroney, says the span can endure a massive quake. “The bridge is incredibly safe, but there are some things we need to do,” he said. “It’s on our shoulders. We have the responsibility to finish what we’ve started.”

Tower troubles

After 32 high-strength steel rods that helped hold down seismic shock absorbers on the span failed in 2013 from water-borne corrosion, Caltrans studied similar rods that anchor the tower to its base.

At the time, Caltrans said the 424 tower rods were not under as much stress as the rods that had failed and were in a dehumidified area that was not exposed to water. Both assertions turned out to be overly optimistic.

Caltrans now acknowledges that at least half the rods were put under greater stress when engineers bent back the tower in 2011 and 2012 to offset the expected pull from the bridge’s heavier and longer eastern side.

As for water damage, Caltrans noticed flooding last year in many of the 25-foot-long rods’ sleeves. It blamed a botched grouting and caulking job by the bridge’s contractor, drained the water and suggested everything was probably fine.

Two recent discoveries cast doubt on those assurances. Tests show one rod may have snapped because of corrosion, and signs of damage have been spotted on two others. And water is flooding back into some of the sleeves, possibly saltwater from the bay. The likely source, experts say, would be bay water infiltrating the concrete foundation through gaps or cracks — endlessly replenishing any water that Caltrans can remove.

Saltwater could threaten the steel reinforcing embedded in the concrete foundation and cause swelling, experts say. That, in turn, could create major cracks in the foundation. The foundation steel rebar is protected with epoxy, but the coating is not foolproof.

Joe Nicoletti, a structural engineer who advised Caltrans during construction, said the foundation and its rods work together to resist the forces on the tower in a catastrophic earthquake.

He said those forces are not great, in part because the deck is seismically isolated from the tower and will sway independently off the main cable. Bridge designers also incorporated many more rods than the span needed, a “belt and suspenders” approach, Nicoletti said.

When Nicoletti assessed the tower foundation for Caltrans in 2012 after questions emerged about its integrity, he concluded it “has a large margin of safety against unforeseen events.”

But on Friday, Nicoletti said the latest problems cut into that safety margin. “You will need some of those rods in a catastrophic earthquake,” he said.

Just how many rods would be needed was discussed at a recent meeting of state and local transportation officials who make up an oversight committee for the project.

Maroney, the chief bridge engineer, said that even with half the rods intact, the tower would only be “perturbed” by a major quake, moving a few inches.

“It will be a little bit deformed, a little bit out of place,” Maroney said. He said a recent analysis showed the tower would tip only slightly, even with no rods at all.

“We regularly put things in that we hope we never use,” Maroney said of the rods, “but they are there just in case.”

David Williams, a consultant who specializes in earthquake engineering for bridges and marine foundations, said he urged two years ago — before the revelations about flooded rod sleeves and possible saltwater intrusion — that bridge officials evaluate the tower’s anchorage for seismic stability.

Williams, who has worked on the BART transbay tube retrofit and plans for the world’s longest suspension bridge, over the Strait of Messina in Italy, said strong earthquakes generate extreme pulses, heaving and side-to-side shaking. Anchor rods are vital safety features, he said.

He said it’s not clear that the Bay Bridge rods can do the job.

“They need to demonstrate that it is actually stable” in the massive quake the bridge is supposed to be able to withstand, Williams said. “Having one tower is inherently unstable — there is only one tower and one cable” to absorb all the forces on the deck.

“I don’t honestly know if it is stable or not,” Williams said. “It’s a huge question. ... If the tower starts to get overstressed and it becomes unstable, it just falls over.”

Bob Bea, an emeritus civil engineering professor at UC Berkeley who studies why major infrastructures fail, said he has reviewed Caltrans’ findings that estimate the quake forces on the tower and is not satisfied.

Caltrans must explain why it needed so many rods in the first place, he said, before suggesting that the tower can safely stay in place without them.

Officials say the rods were installed out of an abundance of caution.

“Obviously it is beyond what we absolutely needed — they were looking for absolutely no uplift,” Maroney said of the bridge designers.

“We would like to have no damage,” Maroney said. But a bit of shifting “is acceptable.”

Deck concerns

As Caltrans seeks to get to the bottom of the tower-rod problem, experts warn it has another major earthquake concern: substandard welded joints that attach deck sections to each other on the suspension span.

The welds hold together 14 giant steel boxes that form the two bridge decks. Several of the boxes, which were made in China, did not fit together neatly when they were assembled at the bridge site. To make them work, Caltrans approved welding that did not measure up to the agency’s own bridge code, officials have acknowledged.

Even the chief designer of the span, Marwan Nader, admitted in a 2011 briefing to bridge officials that some of the problem joints will probably suffer “local damage” in a big earthquake.

Roumen Mladjov, a structural engineer and bridge builder who served on the advisory panel that picked the Bay Bridge design in 1998, said the welds joining the misaligned deck sections create unneeded stresses on the span.

Caltrans officials told him the misaligned stretches are limited and do not pose a significant hazard, he said. “They say they are very local and extend a few millimeters here or there,” Mladjov said.

He disagrees, saying larger sections of the decks are at risk.

And there are other problems, Mladjov said — steel bars that were installed under the bridge during construction to make it easier for workers to weld sections together. They were designed to be temporary, but Caltrans modified the bridge plans so they could remain.

In a quake, those bars can concentrate shaking forces and put the bridge in greater danger, Mladjov said. Engineers who studied collapsed structures after the Northridge earthquake in 1994 concluded that similar steel bars had contributed to some of the failures.

In a letter last month to bridge officials, Mladjov warned, “It is obvious that for this bridge all, or most, of the safety margins are already exhausted. This is unacceptable for any new bridge structure and specifically for the S.F.-Oakland Bay Bridge, which is the busiest bridge in the Bay Area.”

Mladjov was responding to an April 1 letter from the executive director of the Metropolitan Transportation Commission, Steve Heminger, who told the engineer that he was “satisfied that the concerns you addressed have been dealt with during the design oversight of the construction activities.”

“It is my belief that the new east span, with proper maintenance, will last the design life and beyond,” and will survive any large earthquake, Heminger said.

Heminger did not return phone calls, but there are indications that his confidence in the bridge has been shaken. After The Chronicle reported news of the potential saltwater intrusion into the tower foundation last week, Heminger told KPIX-TV that the bridge was “the project from hell.”

Maroney said he is convinced the bridge’s joints can handle extreme seismic loads. As for the margin of safety, he said, “I think you have plenty.”

Leaks at cable rods

Also causing seismic concerns for Caltrans are leaks in the guardrail system on the suspension span, allowing water to reach some of the 274 steel rods anchoring the main cable.

The rods are fused with bundles of steel cable and then bolted to steel blocks inside the belly of the span. For more than a year during construction, they were exposed to the open air.

The rods are critical because they alone would hold the cable in place during an earthquake. Caltrans said the rods are now in a dehumidified zone, but one expert who has examined powdery residue found on them says the leaks are already causing corrosion.

“There’s a lot of rust on the rods,” said Yun Chung, a retired engineer with Bechtel who advised the firm about using bolts in massive infrastructure projects. “They have been under high humidity for some time.”

Several of the rods shifted during construction when the bridge decks were suspended from the cable, putting them perilously close to the walls of the steel blocks. In an earthquake, they could bang into the blocks and be damaged.

Caltrans recently ordered that the rods be adjusted to try to move them away from the blocks.

“It’s not just one area that concerns me,” Chung said. “The bridge still can be saved, if a corrosion specialist takes a detailed tour and they identify all of the weak points and take measures to deal with the issues. Once things start to corrode, there’s no turning back.”

Maroney said that Caltrans will address the leaks before any significant corrosion damage is inflicted.

“You can’t ignore it,” Maroney said. “We don’t need to spend taxpayer money like it’s an emergency, but we need to zip up the bridge.”

He added, “As a bridge engineer, I know that steel and water don’t mix. My goal is to have it zipped up ... before the next rainy season.”

Engineers see the cascade of corrosion and weld-related problems on the span as warning signs that the seismic risk is real.

Bea, the UC Berkeley expert, said Caltrans has to break out of what he called its reactive mode.

“We don’t know if the bridge is safe — that is the part that I’ll call concerning,” he said. “Until somebody takes a deep breath and performs a comprehensive set of analyses, we won’t truly know that it is safe.”

Jaxon Van Derbeken is a San Francisco Chronicle staff writer. E-mail: jvanderbeken@sfchronicle.com