Dispute over Bay Bridge cracks

Leaks invade foundation — risks, repairs debated

It wasn’t long after workers finished pouring concrete at the bottom of the new eastern Bay Bridge’s tower foundation that the cracks emerged.

Some of the fissures that began to show up in April 2007 were minor, but the two largest were anything but — they were more than 10 feet long and cut through the 20-inch-thick, steel-bar-reinforced concrete layer designed to block corrosive salt water from reaching the foundation frame and tower anchor bolts that provide stability in a major earthquake.

Caltrans made what turned out to be a crucial decision that spring: Rather than demolish the crack-riddled slab and start over, it approved the contractor’s plan to

inject the fissures with industrial-grade glue.

Now the concrete repair has failed, and water is flowing into the foundation and filling the sleeves that hold the 25foot-long rods anchoring the tower. Some of the 400-plus rods have developed rust and micro-cracks, and at least one rod has broken.

Confronted with the stubborn flooding, Caltrans and the three-official panel that oversees the eastern span project recently made another potentially fateful decision: They would study a way to deal with the rods, but not install equipment that could detect and even counter the threat of water-borne corrosion to the foundation itself, overriding the advice of federal highway officials and some of the state’s own engineering consultants.

Caltrans confident

Caltrans and the bridge’s design firm maintain that the foundation’s steel frame is robust enough to do its main job — provide stability in a major earthquake — even if it is beset by corrosion.

“We continue to have complete confidence” that if salt water keeps invading the foundation, the structure can “withstand a 1,500-year seismic event throughout the 150year bridge design life,” Robert Dameron, an engineer with the design firm joint venture T.Y. Lin International/Moffatt and Nichol, wrote in a September memo to Caltrans officials.

But experts outside Caltrans say there is no way to be sure the foundation can retain its strength, given the unpredictability of saltwater corrosion’s effects inside steel-and-concrete structures.

“You don’t want to shrug it off,” said Jack Tinnea, a 35year veteran bridge-corrosion consultant who has worked with government agencies and companies on marine projects from Alaska to Mexico. “I have no idea where (the water) is traveling, and neither do they.”

Running late

When the foundation concrete cracks emerged in 2007, Caltrans quickly realized that 22 of them were wider than the agency deemed acceptable. But the bridge project was already behind schedule, and ordering the foundation rebuilt would have added months to the job.

Instead, Caltrans had the cracks filled with highstrength industrial glue, then lowered the structure into the bay.

By 2014, water started showing up in the sleeves that hold the 25-foot-long anchor rods. At first the source appeared to be rain, but later tests showed it was salt water seeping in through the foundation.

After convening a panel of experts, Caltrans officials downplayed the flooding danger to the foundation, which now sits atop 13 steel-and-concrete piles driven into the bay floor.

“I think concrete is gray and it cracks — and every concrete pile cap will crack,” said Caltrans’ chief engineer on the bridge project, Brian Maroney, referring to the foundation frame.

“I expect some — a very small amount of — water to get in there,” he said.

Caltrans isn’t convinced that the micro-cracks found on many of the foundation rods make them vulnerable to premature failure, although several outside experts have said they could be. It’s also not convinced that the fact that one tower anchor rod snapped is any sign that other rods are in jeopardy.

As a result, Maroney said, Caltrans shouldn’t worry about trying to shore up the foundation cracks with better glue. Plugging the base of the rod sleeves, he believes, will keep new water from being drawn into the foundation.

Inspections seen as difficult

Once that is finished, all Caltrans needs to do is to have scuba divers periodically check the concrete surrounding the foundation for signs of new corrosion and damage, Maroney told the three-official bridge oversight panel in October.

“Essentially, you accomplish the intent of this particular investigation through ongoing maintenance?” Will Kempton, the head of the state Transportation Commission and a member of the oversight panel, asked Maroney. “Yes sir,” Maroney replied. Several outside experts, however, said there are risks to that plan. For starters, the foundation is now encrusted with barnacles and other sea life that cover up the concrete, potentially blocking any damage from the view of scuba divers.

“The question is where the concrete is not sound,” said Tinnea, who wrote a 2011 guide for corrosion control in bridges for the National Association of Corrosion Engineers. “Clearly, they have concrete that is not sound if they have water coming in.

“Anywhere the water passes they are going to have accelerated corrosion,” Tinnea said, “which could lead to dramatic section loss — we see it way too often.”

Monitoring equipment

Tinnea said Caltrans should try to seal the cracked concrete foundation base — not with industrial-grade glue, but with a rubberized material capable of expanding and keeping water out.

At the very least, Tinnea and other bridge-engineering experts said, Caltrans should install monitoring equipment inside the foundation to try to

Lurking undetected

detect any corrosion — an idea that the bridge oversight panel rejected last month after Maroney gave assurances that Caltrans scuba divers could do the job with visual checks.

A relatively inexpensive corrosion monitoring system could easily detect the telltale electrical current given off by the corrosion process and alert bridge officials to the extent of the problem, said Lawrence Kahn, a Georgia Tech professor of structural engineering and expert in concrete durability.

“You should monitor significant structures,” Kahn said. “This is a significant structure. You don’t know how much this is going to corrode. The cost of maintaining and monitoring is infinitesimal compared to the cost of failure.”

It’s difficult to predict whether corrosion is already brewing in the foundation, even if Caltrans is correct that the anchor rods have not fallen victim and the steel skeleton has ample margin for error, said Preet Singh, an engineering professor at Georgia Tech who specializes in concrete and corrosion.

Corrosion may thrive underneath concrete for years before being discovered, Singh said.

“They have to have an active corrosion monitoring system,” he said. “If there is a confined space, corrosion cannot be predicted.”

Bob Bea, an emeritus professor of civil engineering at UC Berkeley and a risk-analysis expert, agreed that corrosion often defies formulas and prediction models.

“There are very, very high uncertainties,” Bea said. “One of the most maddening things about corrosion and salt water is that it routinely occurs where you don’t expect it.”

Experts say that should Caltrans find corrosion, it could counter the problem with a system that would charge the steel structure with electricity. That current would short-circuit the corrosion reaction.

Tinnea pointed out that Caltrans has plenty of experience with such a corrosion-fighting system. In 1983, it installed one at the base of the Richmond-San Rafael Bridge.

But Caltrans’ Maroney told the bridge oversight panel that underwater visual checks will suffice. He said he would make sure Caltrans’ maintenance unit “never forgets” about the need to check for foundation damage.

Besides, he told the oversight panel, even a corroded steel frame could fulfill its seismic mission.

“There is an abundance of capacity,” Maroney said, “and I feel very comfortable with it.”

He said a monitoring system would be valuable only many years in the future, possibly after the bridge’s expected 150-year life span.

That went against the advice of a team of federal highway officials, two bridge experts who served on a peer advisory panel to Caltrans and the bridge’s design engineering firm. They have all raised the idea of monitoring the foundation for corrosion.

Rust danger

T.Y. Lin International/Moffatt and Nichol, the design engineering firm, told a panel of bridge and corrosion experts in July that Caltrans should consider both corrosion monitoring and, “if needed,” a system to prevent corrosion on the structure.

The firm said the foundation’s concrete should form a naturally corrosion-resistant layer because it is highly alkaline, allowing it to serve as a chemical barrier to the corrosive effects of salt water.

But with the flooding that is already happening, the firm acknowledged, rust could form “in discrete, localized patches.” The rust can swell the steel many times its volume and push against the concrete, causing it to bend or crack, the firm said.

However, the firm told Caltrans in its September memo that the foundation steel frame has twice the strength it needs to ride out a large earthquake, so it could suffer extensive corrosion and still do its job.

Backup checks

The memo’s author, Dameron, did not address his firm’s earlier advice that Caltrans consider monitoring and protection equipment. Reached by phone, he referred questions to Caltrans.

Two bridge experts on the Caltrans advisory panel that met in July also backed the idea of corrosion monitoring. Bob Bittner — a veteran engineer and marine foundation consultant — said he was satisfied that the 20-inch layer of concrete was sufficient to protect the structure, and told fellow experts that corrosion there “is not considered a concern.”

But he urged that the agency develop a plan to “monitor corrosion and arrest corrosion should it become an issue.”

Another veteran bridge design and engineering expert and Caltrans adviser, John Kulicki, called for a “plan to monitor active corrosion and consider contingency plans of what to do in case of finding” it.

Feds urge plan

Kulicki did not respond to a call seeking comment. Bittner referred questions to Caltrans.

In September, a Federal Highway Administration official, Vince Mammano, told the three-official bridge oversight panel that Caltrans should track the flooding rate into the foundation and consider installing an electrically charged system to circumvent the chemical reaction that causes corrosion.

“We’re encouraging a plan to apply continuing corrosion protection” to the foundation, Mammano told the oversight panel, whose members include Kempton of the state Transportation Commission, Caltrans chief Will Dougherty and Steve Heminger, head of the Metropolitan Transportation Commission.

“Some of the maintenance opportunities I think would include evaluating the benefit of (a corrosion protection system) for the piles and looking for longer-term (corrosion protection) in the bridge,” Mammano said. “There’s been some discussion back and forth with the team on that.”

For experts like Bea, the UC Berkeley emeritus professor, Caltrans must do more than just wait and see if corrosion problems materialize.

“This is still a mess. It is not acceptable,” Bea said. “We have got ample evidence of potentially important challenges to the strength of this system.

“Stopping the water is No. 1,” he said. “That is the source of our corrosion threat.”